Current Shareware 1994 January/SHAR194.ISO/sys_util/inter37a.zip/INTERRUP.D

Text File | 1993-10-03 | 345KB | 9,260 lines

Interrupt List, part 4 of 10
This compilation is Copyright (c) 1989,1990,1991,1992,1993 Ralf Brown
--------D-2142-------------------------------
INT 21 - DOS 2+ - "LSEEK" - SET CURRENT FILE POSITION
    AH = 42h
    AL = origin of move
        00h start of file
        01h current file position
        02h end of file
    BX = file handle
    CX:DX = offset from origin of new file position
Return: CF clear if successful
        DX:AX = new file position in bytes from start of file
    CF set on error
        AX = error code (01h,06h) (see AH=59h)
Notes:    for origins 01h and 02h, the pointer may be positioned before the
      start of the file; no error is returned in that case, but subsequent
      attempts at I/O will produce errors
    if the new position is beyond the current end of file, the file will
      be extended by the next write (see AH=40h)
BUG:    using this method to grow a file from zero bytes to a very large size
      can corrupt the FAT in some versions of DOS; the file should first
      be grown from zero to one byte and then to the desired large size
SeeAlso: AH=24h,INT 2F/AX=1228h
--------v-214203-----------------------------
INT 21 - VIRUS - "Shake" - INSTALLATION CHECK
    AX = 4203h
Return: AX = 1234h if resident
SeeAlso: AX=3DFFh,AX=4243h
--------v-214243-----------------------------
INT 21 - VIRUS - "Invader" - INSTALLATION CHECK
    AX = 4243h
Return: AX = 5678h if resident
SeeAlso: AX=4203h,AX=4B04h
--------D-214300-----------------------------
INT 21 - DOS 2+ - GET FILE ATTRIBUTES
    AX = 4300h
    DS:DX -> ASCIZ filename
Return: CF clear if successful
        CX = file attributes (see AX=4301h)
        AX = CX (DR-DOS 5.0)
    CF set on error
        AX = error code (01h,02h,03h,05h) (see AH=59h)
Notes:    under the FlashTek X-32 DOS extender, the filename pointer is in DS:EDX
    under DR-DOS 3.41 and 5.0, attempts to change the subdirectory bit are
      simply ignored without an error
SeeAlso: AX=4301h,AX=4310h,AH=B6h,INT 2F/AX=110Fh
--------D-214301-----------------------------
INT 21 - DOS 2+ - "CHMOD" - SET FILE ATTRIBUTES
    AX = 4301h
    CX = new file attributes (see below)
    DS:DX -> ASCIZ filename
Return: CF clear if successful
        AX destroyed
    CF set on error
        AX = error code (01h,02h,03h,05h) (see AH=59h)
Notes:    will not change volume label or directory attribute bits, but will
      change the other attribute bits of a directory (the directory
      bit must be cleared to successfully change the other attributes of a
      directory, but the directory will not be changed to a normal file as
      a result)
    MS-DOS 4.01 reportedly closes the file if it is currently open
    for security reasons, the Novell NetWare execute-only bit can never
      be cleared; the file must be deleted and recreated
    under the FlashTek X-32 DOS extender, the filename pointer is in DS:EDX
    DOS 5.0 SHARE will close the file if it is currently open in sharing-
      compatibility mode, otherwise a sharing violation critical error is
      generated if the file is currently open
SeeAlso: AX=4300h,AX=4311h,INT 2F/AX=110Eh

Bitfields for file attributes:
 bit 7    shareable (Novell NetWare)
 bit 6    unused
 bit 5    archive
 bit 4    directory
 bit 3    volume label
    execute-only (Novell NetWare)
 bit 2    system
 bit 1    hidden
 bit 0    read-only
--------O-214302-----------------------------
INT 21 - DR-DOS 3.41+ internal - GET ACCESS RIGHTS
    AX = 4302h
    DS:DX -> ASCIZ pathname
Return: CF clear if successful
        CX = access rights (see below)
        AX = CX (DR-DOS 5.0)
    CF set on error
        AX = error code
Desc:    Determine which operations the calling program may perform on a
      specified file without being required to provide a password.
Notes:    this protection scheme has been coordinated on all current Digital
      Research/Novell operating systems (DR-DOS 3.41+, DRMDOS 5.x, and
      FlexOS 2+)
    this function is documented in DR-DOS 6.0 and corresponds to the
      "Get/Set File Attributes" function, subfunction 2, documented in
      Concurrent DOS.
    only FlexOS actually uses the "execution" bits; DR-DOS 3.41+ treats
      them as "read" bits.
    DR-DOS 3.41-5.x only use bits 0-3.  Only DR-DOS 6.0 using a
      DRMDOS 5.x security system allowing for users and groups uses bits
      4-11.
SeeAlso: AX=4303h

Bitfields for access rights:
 bit 0    owner delete requires password
 bit 1    owner execution requires password (FlexOS)
 bit 2    owner write requires password
 bit 3    owner read requires password
 bit 4    group delete requires password
 bit 5    group execution requires password (FlexOS)
 bit 6    group write requires password
 bit 7    group read requires password
 bit 8    world delete requires password
 bit 9    world execution requires password (FlexOS)
 bit 10 world write requires password
 bit 11 world read requires password
--------O-214303-----------------------------
INT 21 - DR-DOS 3.41+ internal - SET ACCESS RIGHTS AND PASSWORD
    AX = 4303h
    CX = access rights
         bits 11-0: access rights (see AX=4302h)
         bit 15: new password is to be set
    DS:DX -> ASCIZ pathname
    [DTA] = new password if CX bit 15 is set (blank-padded to 8 characters)
Return: CF clear if successful
    CF set on error
        AX = error code
Notes:    if the file is already protected, the old password must be added after
      the pathname, separated by a ";"
    this function is documented in DR-DOS 6.0 and corresponds to the
      "Get/Set File Attributes" function, subfunction 3, documented in
      Concurrent DOS.
SeeAlso: AH=0Fh,AH=17h,AX=4302h,AX=4305h,AX=4454h
--------O-214304-----------------------------
INT 21 U - DR-DOS 5.0-6.0 internal - GET ENCRYPTED PASSWORD
    AX = 4304h
    DS:DX -> ASCIZ filename
    ???
Return: CF clear if successful
        CX = AX = 0000h if no password assigned to file
    CF set on error
        AX = error code (see AH=59h)
Note:    this function is only supported by DR-DOS 5.0 and 6.0 and DRMDOS 5.1
SeeAlso: AX=4303h,AX=4305h
--------O-214305-----------------------------
INT 21 U - DR-DOS 5.0-6.0 internal - SET EXTENDED FILE ATTRIBUTES
    AX = 4305h
    DS:DX -> ASCIZ filename
    ???
Return: CF clear if successful
    CF set on error
        AX = error code (see AH=59h)
Desc:    this function allows the extended attributes, and optionally the
      encrypted password, of a file to be set.
Note:    this function is only supported by DR-DOS 5.0 and 6.0 and DRMDOS 5.1
SeeAlso: AX=4304h,AX=4311h
--------O-214306-----------------------------
INT 21 - DR-DOS 6.0 - GET FILE OWNER
    AX = 4306h
    DS:DX -> ASCIZ filename
Return: CF clear if successful
        AX = CX = value set with AX=4307h
    CF set on error
        AX = error code (see AH=59h)
SeeAlso: AX=4307h
--------O-214307-----------------------------
INT 21 - DR-DOS 6.0 - SET FILE OWNER
    AX = 4307h
    CX = ??? (owner identification number?)
    DS:DX -> ASCIZ filename
Return: CF clear if successful
    CF set on error
        AX = error code (see AH=59h)
SeeAlso: AX=4306h
--------N-214310-----------------------------
INT 21 - Banyan VINES 2.1+ - GET EXTENDED FILE ATTRIBUTES
    AX = 4310h
    DS:DX -> ASCIZ filename
Return: CF clear if successful
        CH = attributes (see AX=4311h)
    CF set on error
        AX = error code (01h,02h,03h,05h) (see AH=59h)
Note:    the filename may be a directory but must be on a VINES file service
SeeAlso: AX=4300h,AX=4311h,AH=B6h,INT 2F/AX=110Fh
--------N-214311-----------------------------
INT 21 - Banyan VINES 2.1+ - SET EXTENDED FILE ATTRIBUTES
    AX = 4311h
    CH = new attributes
        bit 7: unused
        bit 6: shareable
        bit 5: execute-only
        bits 4-0: unused
    DS:DX -> ASCIZ filename
Return: CF clear if successful
    CF set on error
        AX = error code (01h,02h,03h,05h) (see AH=59h)
Note:    the filename may be a directory but must be on a VINES file service
SeeAlso: AX=4301h,AX=4305h,AX=4310h,INT 2F/AX=110Eh
----------214380-----------------------------
INT 21 - Novell DOS 7 - UNDELETE PENDING DELETE FILE
    AX = 4380h
    ???
Return: ???
SeeAlso: AH=41h,AX=4381h
----------214381-----------------------------
INT 21 - Novell DOS 7 - PURGE PENDING DELETE FILE
    AX = 4381h
    ???
Return: ???
SeeAlso: AH=41h,AX=4380h
--------D-214400-----------------------------
INT 21 - DOS 2+ - IOCTL - GET DEVICE INFORMATION
    AX = 4400h
    BX = handle
Return: CF clear if successful
        DX = device information word (see below)
        AX destroyed
    CF set on error
        AX = error code (01h,05h,06h) (see AH=59h)
Notes:    value in DH corresponds to high byte of device driver's attribute word
      if handle refers to a character device
    Novell NetWare reportedly does not return a drive number in bits 5-0
      for a disk file
SeeAlso: AX=4401h,INT 2F/AX=122Bh

Bitfields for device information word:
 character device
  bit 14: device driver can process IOCTL requests (see AX=4402h)
  bit 13: output until busy supported
  bit 11: driver supports OPEN/CLOSE calls
  bit  7: set (indicates device)
  bit  6: EOF on input
  bit  5: raw (binary) mode
  bit  4: device is special (uses INT 29)
  bit  3: clock device
  bit  2: NUL device
  bit  1: standard output
  bit  0: standard input
 disk file
  bit 15: file is remote (DOS 3+)
  bit 14: don't set file date/time on closing (DOS 3+)
  bit 11: media not removable
  bit  8: (DOS 4 only) generate INT 24 if no disk space on write or read past
        end of file
  bit  7: clear (indicates file)
  bit  6: file has not been written
  bits 5-0: drive number (0 = A:)
--------D-214401-----------------------------
INT 21 - DOS 2+ - IOCTL - SET DEVICE INFORMATION
    AX = 4401h
    BX = handle (must refer to character device)
    DX = device information word (see AX=4400h)
        (DH must be zero)
Return: CF clear if successful
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4400h,INT 2F/AX=122Bh
--------D-214402-----------------------------
INT 21 - DOS 2+ - IOCTL - READ FROM CHARACTER DEVICE CONTROL CHANNEL
    AX = 4402h
    BX = file handle referencing character device
    CX = number of bytes to read
    DS:DX -> buffer
Return: CF clear if successful
        AX = number of bytes actually read
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    format of data is driver-specific (see below for some specific cases)
SeeAlso: AX=4400h,AX=4403h,AX=4404h,INT 2F/AX=122Bh
--------N-214402-----------------------------
INT 21 - Network Driver Interface Specification (NDIS) 2.0.1 - PROTOCOL MANAGER
    AX = 4402h
    BX = file handle for device "PROTMAN$"
    CX = 000Eh (size of request block)
    DS:DX -> request block (see below)
Return: CF clear if successful
        AX = number of bytes actually read
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h"FTPSOFT"

Format of request block for GetProtocolManagerInfo:
Offset    Size    Description
 00h    WORD    01h
 02h    WORD    returned status (see below)
 04h    DWORD    returned pointer to structure representing parsed user config
 08h    DWORD    unused
 0Ch    WORD    returned BCD version of NDIS on which Protocol Manager is based

Format of request block for RegisterModule:
Offset    Size    Description
 00h    WORD    02h
 02h    WORD    returned status (see below)
 04h    DWORD    pointer to module's common characteristics table (see below)
 08h    DWORD    pointer to list of modules to which the module is to be bound
 0Ch    WORD    unused

Format of request block for BindAndStart:
Offset    Size    Description
 00h    WORD    03h
 02h    WORD    returned status (see below)
 04h    DWORD    caller's virtual address in FailingModules structure
 08h    DWORD    unused
 0Ch    WORD    unused

Format of request block for GetProtocolManagerLinkage:
Offset    Size    Description
 00h    WORD    04h
 02h    WORD    returned status (see below)
 04h    DWORD    returned dispatch point
 08h    DWORD    unused
 0Ch    WORD    returned protocol manager DS
Note:    the dispatch point may be called as follows instead of using this IOCTL
    STACK: WORD  protocol manager DS
           DWORD pointer to request block
    Return: AX = returned status
        STACK popped

Format of request block for GetProtocolIniPath:
Offset    Size    Description
 00h    WORD    05h
 02h    WORD    returned status (see below)
 04h    DWORD    pointer to a buffer for the ASCIZ pathname of PROTOCOL.INI
 08h    DWORD    unused
 0Ch    WORD    buffer length

Format of request block for RegisterProtocolManagerInfo:
Offset    Size    Description
 00h    WORD    06h
 02h    WORD    returned status (see below)
 04h    DWORD    pointer to structure containing parsed user config file
 08h    DWORD    unused
 0Ch    WORD    length of structure

Format of request block for InitAndRegister:
Offset    Size    Description
 00h    WORD    07h
 02h    WORD    returned status (see below)
 04h    DWORD    unused
 08h    DWORD    poitner to ASCIZ name of the module to be prebind initialized
 0Ch    WORD    unused

Format of request block for UnbindAndStop:
Offset    Size    Description
 00h    WORD    08h
 02h    WORD    returned status (see below)
 04h    DWORD    failing modules as for BindAndStart
 08h    DWORD    if not 0000h:0000h, pointer to ASCIZ name of module to unbind
        if 0000h:0000h, terminate a set of previously dynamically
          bound protocol modules
 0Ch    WORD    unused

Format of request block for BindStatus:
Offset    Size    Description
 00h    WORD    09h
 02h    WORD    returned status (see below)
 04h    DWORD    must be 0000h:0000h
        on return, points to root tree
 08h    DWORD    0000h:0000h
 0Ch    WORD    unused under DOS

Format of request block for RegisterStatus:
Offset    Size    Description
 00h    WORD    0Ah
 02h    WORD    returned status (0000h, 0008h, 002Ch) (see below)
 04h    DWORD    0000h:0000h
 08h    DWORD    pointer to 16-byte ASCIZ module name
 0Ch    WORD    0000h
Note:    not supported by the 10NET v5.0 PROTMAN$ driver

Values for status code:
 0000h    success
 0001h    wait for release--protocol has retained control of the data buffer
 0002h    request queued
 0003h    frame not recognized
 0004h    frame rejected
 0005h    frame should be forwarded
 0006h    out of resource
 0007h    invalid parameter
 0008h    invalid function
 0009h    not supported
 000Ah    hardware error
 000Bh    transmit error
 000Ch    unrecognized destination
 000Dh    buffer too small
 0020h    already started
 0021h    binding incomplete
 0022h    driver not initialized
 0023h    hardware not found
 0024h    hardware failure
 0025h    configuration failure
 0026h    interrupt conflict
 0027h    MAC incompatible
 0028h    initialization failed
 0029h    no binding
 002Ah    network may be disconnected
 002Bh    incompatible OS version
 002Ch    already registered
 002Dh    path not found
 002Eh    insufficient memory
 002Fh    info not found
 00FFh    general failure
 F000h-FFFFh reserved for vendor-specific codes, treated as general failure

Format of common characteristics table:
Offset    Size    Description
 00h    WORD    size of table in bytes
 02h    BYTE    NDIS major version
 03h    BYTE    NDIS minor version
 04h    WORD    reserved
 06h    BYTE    module major version
 07h    BYTE    module minor version
 08h    DWORD    module function flag bits
        bit 0: binding at upper boundary supported
        bit 1: binding at lower boundary supported
        bit 2: dynamically bound
        bits 3-31 reserved, must be 0
 0Ch 16 BYTEs    ASCIZ module name
 1Ch    BYTE    upper boundary protocol level (see below)
 1Dh    BYTE    upper boundary interface type
        for MACs: 1 = MAC
        for data links and transports: to be defined
        for session: 1 = NCB
        any level: 0 = private (ISV-defined)
 1Eh    BYTE    lower boundary protocol level (see below)
 1Fh    BYTE    lower boundary interface type
        same as offset 1Dh
 20h    WORD    module ID filled in by protocol manager
 22h    WORD    module DS
 24h    DWORD    system request entry point
 28h    DWORD    pointer to service-specific characteristics
        0000h:0000h if none
 2Ch    DWORD    pointer to service-specific status, or 0000h:0000h if none
 30h    DWORD    pointer to upper dispatch table (see below)
        0000h:0000h if none
 34h    DWORD    pointer to lower dispatch table (see below)
        0000h:0000h if none
 38h  2 DWORDs    reserved, must be 0
Note:    for compatibility with NDIS 1.x.x, a major version of 00h is
      interpreted as 01h

Values for boundary protocol level:
 00h    physical
 01h    Media Access Control
 02h    Data link
 03h    network
 04h    transport
 05h    session
 FFh    not specified

Format of dispatch table:
Offset    Size    Description
 00h    DWORD    -> common characteristics table (see above)
 04h  4 BYTEs    ???
 08h    DWORD    -> ??? function (called with 12 bytes of stack arguments)
 0Ch    DWORD    -> ??? function (called with 10 bytes of stack arguments)
 10h    DWORD    -> ??? function (called with 16 bytes of stack arguments)
 14h    DWORD    -> ??? function (called with 4 bytes of stack arguments)
 18h    DWORD    -> ??? function (called with 18 bytes of stack arguments)
 1Ch    DWORD    -> ??? function (called with 12 bytes of stack arguments)

Format of MAC Service-Specific Characteristics Table:
Offset    Size    Description
 00h    WORD    length of table in bytes
 02h 16 BYTEs    ASCIZ MAC type name, "802.3", "802.4", "802.5", "802.6", "DIX",
        "DIX+802.3", "APPLETALK", "ARCNET", "FDDI", "SDLC", "BSC",
        "HDLC", or "ISDN"
 12h    WORD    length of station addresses in bytes
 14h 16 BYTEs    permanent station address
 24h 16 BYTEs    current station address
 34h    DWORD    current functional adapter address (00000000h if none)
 38h    DWORD    pointer to multicast address list
 3Ch    DWORD    link speed in bits/sec
 40h    DWORD    service flags (see below)
 44h    WORD    maximum frame size which may be both sent and received
 46h    DWORD    total transmit buffer capacity in bytes
 4Ah    WORD    transmit buffer allocation block size in bytes
 4Ch    DWORD    total receive buffer capacity in bytes
 50h    WORD    receive buffer allocation block size in bytes
 52h  3 BYTEs    IEEE vendor code
 55h    BYTE    vendor adapter code
 56h    DWORD    pointer to ASCIZ vendor adapter description
 5Ah    WORD    IRQ used by adapter
 5Ch    WORD    transmit queue depth
 5Eh    WORD    maximum supported number of data blocks in buffer descriptors
 60h  N BYTEs    vendor-specific info

Bitfields for service flags:
 bit 0    supports broadcast
 bit 1    supports multicast
 bit 2    supports functional/group addressing
 bit 3    supports promiscuous mode
 bit 4    station address software settable
 bit 5    statistics always current
 bit 6    supports InitiateDiagnostics
 bit 7    supports loopback
 bit 8    MAC does primarily ReceiveChain indications instead of ReceiveLookahead
    indications
 bit 9    supports IBM source routing
 bit 10 supports MAC reset
 bit 11 supports Open/Close adapter
 bit 12 supports interrupt request
 bit 13 supports source routing bridge
 bit 14 supports GDT virtual addresses (OS/2 version)
 bit 15 multiple TransferDatas allowed durign a single indication
 bit 16 MAC normally sets FrameSize = 0 in ReceiveLookahead
 bit 17-31 reserved, must be 0

Format of NetBIOS Service-Specific Characteristics Table
Offset    Size    Description
 00h    WORD    length of table in bytes
 02h 16 BYTEs    ASCIZ type name of NetBIOS module
 12h    WORD    NetBIOS module code
 14h  N BYTEs    vendor-specific info

Format of MAC Service-Specific Status Table:
Offset    Size    Description
 00h    WORD    length of table in bytes
 02h    DWORD    seconds since 0:00 1/1/70 when diagnostics last run
        (FFFFFFFFh = never)
 06h    DWORD    MAC status bits (see below)
 0Ah    WORD    current packet filter flags
        bit 0: directed/multicast or group/functional
        bit 1: broadcast
        bit 2: promiscuous
        bit 3: all source routing
        bits 4-15: reserved, must be zero
 0Ch    DWORD    pointer to media-specific status table or 0000h:0000h
 10h    DWORD    seconds past 0:00 1/1/70 of last ClearStatistics
 14h    DWORD    total frames received (FFFFFFFFh = not counted)
 18h    DWORD    frames with CRC error (FFFFFFFFh = not counted)
 1Ch    DWORD    total bytes received (FFFFFFFFh = not counted)
 20h    DWORD    frames discarded--no buffer space (FFFFFFFFh = not counted)
 24h    DWORD    multicast frames received (FFFFFFFFh = not counted)
 28h    DWORD    broadcast frames received (FFFFFFFFh = not counted)
 2Ch    DWORD    frames with errors (FFFFFFFFh = not counted)
 30h    DWORD    overly large frames (FFFFFFFFh = not counted)
 34h    DWORD    frames less than minimum size (FFFFFFFFh = not counted)
 38h    DWORD    multicast bytes received (FFFFFFFFh = not counted)
 3Ch    DWORD    broadcast bytes received (FFFFFFFFh = not counted)
 40h    DWORD    frames discarded--hardware error (FFFFFFFFh = not counted)
 44h    DWORD    total frames transmitted (FFFFFFFFh = not counted)
 48h    DWORD    total bytes transmitted (FFFFFFFFh = not counted)
 4Ch    DWORD    multicast frames transmitted (FFFFFFFFh = not counted)
 50h    DWORD    broadcast frames transmitted (FFFFFFFFh = not counted)
 54h    DWORD    broadcast bytes transmitted (FFFFFFFFh = not counted)
 58h    DWORD    multicast bytes transmitted (FFFFFFFFh = not counted)
 5Ch    DWORD    frames not transmitted--timeout (FFFFFFFFh = not counted)
 60h    DWORD    frames not transmitted--hardware error (FFFFFFFFh = not countd)
 64h  N BYTEs    vendor-specific info

Bitfields for MAC status bits:
 bits 0-2    operational status
        000 hardware not installed
        001 hardware failed startup diagnostics
        010 hardware configuration problem
        011 hardware fault
        100 operating marginally due to soft faults
        101 reserved
        110 reserved
        111 hardware fully operational
 bit 3    MAC bound
 bit 4    MAC open
 bit 5    diagnostics in progress
 bits 6-31 reserved
--------I-214402-----------------------------
INT 21 U - IBM SYSTEM 36/38 WORKSTATION EMULATION - VDI.SYS - GET ???
    AX = 4402h
    BX = handle for character device "GDMS"
    CX = number of bytes to read (>= 4)
    DS:DX -> buffer (see below)
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        AX = number of bytes read

Format of returned data:
Offset    Size    Description
 00h  4 BYTEs    ???
 04h    DWORD    pointer to ???
 08h  4 BYTEs    ???
--------m-214402-----------------------------
INT 21 U - LASTBYTE.SYS v1.19 - IOCTL - GET ??? TABLE
    AX = 4402h
    BX = handle for device "LA$TBYTE"
    CX = 0004h
    DS:DX -> DWORD to hold address of 39-byte table of ???
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        AX = number of bytes read
Program: LASTBYTE.SYS is part of the shareware "The Last Byte" memory
      management package by Key Software Products
SeeAlso: AX=4402h"HIGHUMM"
--------m-214402-----------------------------
INT 21 - HIGHUMM.SYS v1.17+ - IOCTL - GET API ADDRESS
    AX = 4402h
    BX = handle for device "KSP$UMM"
    CX = 0004h
    DS:DX -> DWORD to hold entry point
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        AX = number of bytes read
Program: HIGHUMM.SYS is part of the shareware "The Last Byte" memory management
      package by Key Software Products
SeeAlso: AX=4402h"LASTBYTE"

Call HIGHUMM.SYS entry point with:
    AH = 00h allocate UMB (same as XMS function 10h) (see INT 2F/AX=4310h)
        DX = size in paragraphs
        Return: BX = segment number (if successful)
            DX = size of requested block/size of largest block
    AH = 01h deallocate UMB (same as XMS func 11h) (see INT 2F/AX=4310h)
        DX = segment number of UMB
    AH = 02h request a bank-switched memory block
        DX = size in paragraphs
        Return: BX = segment number (if successful)
            DX = size of requested block/size of largest block
    AH = 03h release a bank-switched memory block
        DX = segment number
    AH = 04h transfer data to/from high memory
        DS:SI -> source
        ES:DI -> destination
        CX = length in bytes
        Note: enables bank-switched memory, does the copy, then disables
        bank-switched memory
    AH = 05h get a word from bank-switched memory
        ES:DI -> word to read
        Return: DX = word
    AH = 06h put a word to bank-switched memory
        ES:DI -> word to write
        DX = word
    AH = 07h put a byte to bank-switched memory
        ES:DI -> byte to write
        DL = byte
    AH = 08h enable bank-switched memory
        DS:SI -> 6-byte status save area
    AH = 09h disable bank-switched memory
        DS:SI -> 6-byte save area from enable call (AH=08h)
    AH = 0Ah assign name to UMB or high bank-switched block
        DX = segment number
        DS:SI -> 8-byte blank-padded name
    AH = 0Bh locate UMB block by name
        DS:SI -> 8-byte blank-padded name
        Return: BX = segment number (if successful)
            DX = size of block
    AH = 0Ch locate bank-switched block by name
        DS:SI -> 8-byte blank-padded name
        Return: BX = segment number (if successful)
            DX = size of block
Return: AX = status code
        0001h successful
        0000h failed
        BL = error code
            80h not implemented
            B0h insufficient memory, smaller block available
            B1h insufficient memory, no blocks available
            B2h invalid segment number
Note:    only functions 00h and 01h are always available; the remaining
      functions are only enabled if the proper commandline switch is given
--------c-214402-----------------------------
INT 21 - SMARTDRV.SYS - IOCTL - GET CACHE STATUS
    AX = 4402h
    BX = file handle for device "SMARTAAR"
    CX = number of bytes to read (min 28h)
    DS:DX -> buffer for status record (see below)
Return: CF clear if successful
        AX = number of bytes actually read
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4403h"SMARTDRV",INT 2F/AX=4A10h/BX=0000h

Format of SMARTDRV status record:
Offset    Size    Description
 00h    BYTE    write-through flag (always 01h)
 01h    BYTE    writes should be buffered (always 00h)
 02h    BYTE    cache enabled if 01h
 03h    BYTE    driver type (01h extended memory, 02h expanded)
 04h    WORD    clock ticks between cache flushes (currently unused)
 06h    BYTE    cache contains locked tracks if nonzero
 07h    BYTE    flush cache on INT 19 reboot if nonzero
 08h    BYTE    cache full track writes if nonzero
 09h    BYTE    double buffering (for VDS) state (00h off, 01h on, 02h dynamic)
 0Ah    DWORD    original INT 13 vector
 0Eh    BYTE    minor version number
 0Fh    BYTE    major version number
 10h    WORD    unused
 12h    WORD    sectors read            \
 14h    WORD    sectors already in cache     > may be scaled rather than
 16h    WORD    sectors already in track buffer /  absolute counts
 18h    BYTE    cache hit rate in percent
 19h    BYTE    track buffer hit rate in percent
 1Ah    WORD    total tracks in cache
 1Ch    WORD    number of tracks in use
 1Eh    WORD    number of locked tracks
 20h    WORD    number of dirty tracks
 22h    WORD    current cache size in 16K pages
 24h    WORD    original (maximum) cache size in 16K pages
 26h    WORD    minimum cache size in 16K pages
 28h    DWORD    pointer to byte flag to increment for locking cache contents
--------d-214402-----------------------------
INT 21 - CD-ROM device driver - IOCTL INPUT
    AX = 4402h
    BX = file handle referencing character device for CD-ROM driver
    CX = number of bytes to read
    DS:DX -> control block (see below)
Return: CF clear if successful
        AX = number of bytes actually read
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    the data returned depends on the first byte of the control block; the
      remainder of the control block is filled by the driver
SeeAlso: AX=4403h"CD-ROM",INT 2F/AX=0802h

Values for data being requested:
 00h    device driver header address
 01h    drive head location
 02h    reserved
 03h    error statistics
 04h    audio channel info
 05h    raw drive bytes (uninterpreted and device-specific)
 06h    device status
 07h    sector size
 08h    volume size
 09h    media change status
 0Ah    audio disk info
 0Bh    audio track info
 0Ch    audio Q-Channel info
 0Dh    audio sub-channel info
 0Eh    UPC code

Format of control block:
Offset    Size    Description
 00h    BYTE    data being requested (see above)
---function 00h---
 01h    DWORD    device driver header address (see also AH=52h)
---function 01h---
 01h    BYTE    addressing mode
        00h HSG
        01h Red Book
 02h    DWORD    current location of drive's head
        logical sector number in HSG mode
        frame/second/minute/unused in Red Book mode
        (HSG sector = minute * 4500 + second * 75 + frame - 150)
---function 03h---
 01h  N BYTEs    undefined as of 5 Aug 88 specification
---function 04h---
 01h    BYTE    input channel (0-3) for output channel 0
 02h    BYTE    volume for output channel 0
 03h    BYTE    input channel (0-3) for output channel 1
 04h    BYTE    volume for output channel 1
 05h    BYTE    input channel (0-3) for output channel 2
 06h    BYTE    volume for output channel 2
 07h    BYTE    input channel (0-3) for output channel 3
 08h    BYTE    volume for output channel 3
Notes:    output channels 0 and 1 are left and right, 2 and 3 are left prime and
      right prime; a volume of 00h is off
    the default setting is for each input channel to be assigned to the
      same-numbered output channel at full (FFh) volume
---function 05h---
 01h    BYTE    number of bytes read
 02h 128 BYTEs    buffer for drive bytes
---function 06h---
 01h    DWORD    device parameters (see below)
---function 07h---
 01h    BYTE    read mode
        00h cooked
        01h raw
 02h    WORD    sector size in bytes
---function 08h---
 01h    DWORD    volume size in sectors
---function 09h---
 01h    BYTE    media change status
        00h don't know
        01h media unchanged
        FFh media has been changed
---function 0Ah---
 01h    BYTE    lowest audio track number
 02h    BYTE    highest audio track number
 03h    DWORD    start address of lead-out track (Red Book format)
--function 0Bh---
 01h    BYTE    track number (set by caller)
 02h    DWORD    starting point of track (Red Book format)
 06h    BYTE    track control info
        bits 15,14,12: track type (notice: bits not contiguous!)
            000 two audio channels, no pre-emphasis
            001 two audio channels with pre-emphasis
            010 data track
            100 four audio channels, no pre-emphasis
            101 four audio channels with pre-emphasis
            other reserved
        bit 13: digital copy permitted
---function 0Ch---
 01h    BYTE    CONTROL and ADR byte (as received from drive)
 02h    BYTE    track number
 03h    BYTE    point or index
 04h    BYTE    minute    \
 05h    BYTE    second     > running time within track
 06h    BYTE    frame    /
 07h    BYTE    zero
 08h    BYTE    "AMIN" or "PMIN"     \
 09h    BYTE    "ASEC" or "PSEC"      > running time on disk
 0Ah    BYTE    "AFRAME" or "PFRAME" /
---function 0Dh---
 01h    DWORD    starting frame address (Red Book format)
 05h    DWORD    transfer address
 09h    DWORD    number of sectors to read
Note:    copies 96 bytes of sub-channel info per sector into buffer
---function 0Eh---
 01h    BYTE    CONTROL and ADR byte
 02h  7 BYTEs    UPC/EAN code (13 BCD digits,low-order nybble of last byte is 0)
 09h    BYTE    zero
 0Ah    BYTE    "AFRAME"

Bitfields for device parameters:
 bit 0    door open
 bit 1    door unlocked
 bit 2    supports raw reading in addition to cooked
 bit 3    writable
 bit 4    can play audio/video tracks
 bit 5    supports interleaving
 bit 6    reserved
 bit 7    supports prefetch requests
 bit 8    supports audio channel control
 bit 9    supports Red Book addressing in addition to HSG
 bit 10 audio is playing
--------m-214402-----------------------------
INT 21 - Quarterdeck - QEMM-386 v5+ - GET API ENTRY POINT
    AX = 4402h
    BX = file handle for device "QEMM386$"
    CX = 0004h
    DS:DX -> DWORD buffer for API entry point
Return: CF clear if successful
        buffer filled (see INT 67/AH=3Fh for entry point parameters)
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    Quarterdeck recently (June 1993) documented this function, but the
      documentation incorrectly states that it is only available for
      QEMM 6+
SeeAlso: AX=4402h"HOOKROM",INT 2F/AX=D201h/BX=5145h,INT 67/AH=3Fh
--------Q-214402-----------------------------
INT 21 U - Quarterdeck - HOOKROM.SYS - GET HOOKED VECTOR TABLE
    AX = 4402h
    BX = file handle for device "HOOKROM$"
    CX = 0004h
    DS:DX -> DWORD buffer for address of hooked vector table (see below)
Return: CF clear if successful
        DS:DX buffer filled
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h/SF=01h

Format of hooked vector table entry:
Offset    Size    Description
 00h  5 BYTEs    FAR jump to actual interrupt handler
        (end of table if first byte is not EAh)
 05h    BYTE    interrupt vector number
--------d-214402-----------------------------
INT 21 - Advanced SCSI Programming Interface (ASPI) - INTERFACE
    AX = 4402h
    BX = file handle for device "SCSIMGR$"
    CX = 0004h
    DS:DX -> buffer for function address
Return: CF clear if successful
        AX = 0004h
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    the function address is called with the address of a SCSI Request
      Block on the stack and the caller must clean up the stack
SeeAlso: AX=440Ch"ASPITAPE",INT 11/AH=FFh"WD7000"

Format of SCSI Request Block (64 bytes):
Offset    Size    Description
 00h    BYTE    request number
        00h "HA_INQ"     host adapter inquiry
        01h "GET_TYPE"     get device type
        02h "EXEC_SIO"     execute SCSI I/O
        03h "ABORT_SRB"     abort SRB
        04h "RESET_DEV"     reset SCSI device
        05h "SET_HAPRMS" set host adapter parameters
 01h    BYTE    request status
        00h not done yet
        02h aborted
        04h SCSI I/O error
        80h invalid
        81h no adapter
        82h no device attached
        else status
 02h    BYTE    host adapter ID
 03h    BYTE    request flags
        bit 3: ???
 04h    DWORD    reserved
---request 00h---
 08h    BYTE    (returned) number of host adapters
 09h    BYTE    (returned) target adapter ID
 0Ah 16 BYTEs    (returned) manager ID
 1Ah 16 BYTEs    (returned) adapter ID
 2Ah 16 BYTEs    (returned) parameters
---request 01h---
 08h    BYTE    target ID
 09h    BYTE    logical unit number
 0Ah    BYTE    (returned) device type
        01h streamer
---request 02h---
 08h    BYTE    target ID
 09h    BYTE    logical unit number
 0Ah    DWORD    data allocation length
 0Eh    BYTE    sense allocation length
 0Fh    DWORD    data buffer pointer
 13h    DWORD    next request pointer (for linking)
 17h    BYTE    CDB length
 18h    BYTE    (returned) host adapter status
        11h select timeout
        12h data overrun
        13h bus error
        14h bus failure
 19h    BYTE    (returned) target status
        02h sense data stored in SRB
        08h target busy
        18h reservation error
 1Ah    DWORD    post routine address
 1Eh    WORD    real mode Post DS
 20h    DWORD    SRB pointer
 24h    WORD    reserved
 26h    DWORD    SRB physical address
 2Ah 22 BYTEs    SCSIMGR$ workspace
 40h  N BYTEs    CCB (20-24 bytes)
---request 04h---
 08h    BYTE    target ID
 09h    BYTE    logical unit number
 0Ah 14 BYTEs    reserved
 18h    BYTE    (returned) host adapter status (see above)
 19h    BYTE    (returned) target status (see above)
 1Ah    DWORD    post routine address
 1Eh 34 BYTEs    workspace

Format of CCB:
Offset    Size    Description
 00h    BYTE    command code
        01h rewind
        05h get block size limits
        08h read
        0Ah write
        10h write file marks
        11h SCSI Space (set position?)
        12h SCSI Inquire
        19h erase
        1Bh load/unload media
 01h    BYTE    flags
        bits 4-0: vary by function
        bits 7-5: logical unit number
 02h    BYTE    "adr_1"
 03h    BYTE    "adr_0"
 04h    BYTE    length
 05h    BYTE    control
    ...
 06h/0Ah 14 BYTEs buffer for sense data
--------m-214402-----------------------------
INT 21 U - Qualitas 386MAX v6.00+ - IOCTL INPUT - GET STATE
    AX = 4402h
    BX = file handle for device "386MAX$$"
    CX = number of bytes to read
    DS:DX -> BYTE 03h followed by 386MAX state buffer (see below)
Return: CF clear if successful
        buffer at DS:DX+1 filled
        AX = number of bytes actually copied
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Notes:    if the value given in CX is less than the size of the state record
      (5Ah for v6.01, 66h for v7.00), only a partial state record will be
      returned
    the state is 40h bytes for 386MAX (actually ASTEMM) v2.20 ("386MAX$$"
      did not exist yet, use "QMMXXXX0" and then "EMMXXXX0" instead) and
      56h bytes for v5.11.
    to invoke 386MAX API functions, push DX onto the stack, load DX with
      the word at offset 25h in the returned state, load all other
      registers as needed for the desired function, and execute an
      OUT DX,AL or OUT DX,AX; DX will be set to the pushed value on return
      if it is not otherwise modified by the API function.    For safety,
      in case a function is not supported or 386MAX is not present, SP
      should be saved and restored around the API call.
    Windows 3.1 Standard mode, LAN Manager, and Windows for Workgroups all
      use the 386MAX API; LAN Manager and Windows for Workgroups reportedly
      make some calls incorrectly
SeeAlso: AX=4403h/SF=03h"386MAX",INT 67/AH=3Fh

Format of 386MAX v6.01+ state:
Offset    Size    Description
 -1    BYTE    (call) 03h
 00h  6 BYTEs    signature "386MAX"
 06h  4 BYTEs    version string "N;NN" (i.e. "6;01" for v6.01)
 0Ah    WORD    segment of low-memory portion of 386MAX.SYS
 0Ch  2 BYTEs    ???
 0Eh    WORD    segment of ??? memory block or 0000h
 10h    WORD    bit flags 1 (see below)
 12h    WORD    (v6.01) starting address of video memory in KB
        (v7.00) low memory size in bytes
 14h  2 BYTEs    ???
 16h    WORD    total high DOS memory in KB
 18h  2 BYTEs    ???
 1Ah    WORD    available shared memory in KB
 1Ch    WORD    KBytes extended memory used by 386MAX
 1Eh  2 BYTEs    ???
 20h    WORD    total extended memory in KB
 22h    WORD    IO port to write (OUT DX,AL) to invoke 386MAX INT 15 functions
 24h    WORD    IO port to write (OUT DX,AL) to invoke 386MAX API functions
 26h    WORD    ??? (depends on DOS version)
 28h  2 BYTEs    ???
 2Ah    DWORD    machine type (see below)
 2Eh    WORD    ???
 30h    WORD    ???
 32h    WORD    system configuration flags (see below)
 34h    WORD    debugging flags 1 (see below)
 36h    WORD    debugging flags 2 (see below)
 38h  2 BYTEs    ???
 3Ah    WORD    segment of first MCB in high memory chain???
 3Ch    WORD    feature flags 1 (see below)
 3Eh    WORD    feature flags 2 (see below)
 40h    WORD    feature flags 3 (see below)
 42h    WORD    segment of first 386MAX control block??? (see below)
 44h    WORD    amount of memory to report available on INT 15/AH=88h
 46h  4 BYTEs    ???
 4Ah    WORD    number of K at start of address space swapped with fast
        extended memory (SWAP= parameter)
 4Ch  2 BYTEs    ???
 4Eh    WORD    ???
 50h    WORD    debugging flags 3 (see below)
 52h    DWORD    old INT 21h
 56h    DWORD    pointer to 386MAX's EMS (INT 67h) handler
---386MAX v7.00---
 5Ah    DWORD    KB of extended memory managed by 386MAX
 5Eh    DWORD    bytes of extended memory (EXT= parameter)
 62h  4 BYTEs    ???

Bitfields for bit flags 1:
 bit 1    ???
 bit 2    ???
 bit 3    ??? (cleared by calling INT 67 functions)
 bit 4    high RAM present???
 bit 5    386MAX in AUTO mode
 bit 6    386MAX enabled
 bit 7    386MAX is providing EMS services
 bit 8    ???
 bit 9    A20 enabled??? (see INT 15/AX=2402h)
 bit 10    Weitek support enabled
 bit 11    ???
 bit 12    ???
 bit 13    QPMS has been used
 bit 14    ???
 bit 15    ???

Bitfields for system configuration flags:
 bit 1    ROM compressed???
 bit 3    ???
 bit 5    386MAX loaded into high memory
 bit 6    Microchannel bus
 bit 7    Weitek math coprocessor detected
 bit 11    PC/XT (thus only single 8259 interrupt controller present, DMA only
        in 1st megabyte, etc)
 bit 13    LMLTOP= specified
 bit 15    ???

Bitfields for debugging flags 1:
 bit 0    DEBUG=LED
 bit 1    DEBUG=X67
 bit 2    DEBUG=INV
 bit 3    DEBUG=EMSPTED
 bit 4    DEBUG=JMP
 bit 5    DEBUG=CALL
 bit 6    DEBUG=HLT
 bit 7    DEBUG=PMR
 bit 8    DEBUG=CR3
 bit 9    DEBUG=CAPS or DEBUG=INT
 bit 10    DEBUG=RC
 bit 11    DEBUG=ROM
 bit 12    DEBUG=XM
 bit 13    DEBUG=SOR
 bit 14    DEBUG=XR
 bit 15    DEBUG=EMSERR

Bitfields for debugging flags 2:
 bit 0    DEBUG=ROMSWAP
 bit 1    DEBUG=UNSHADOWROM
 bit 2    DEBUG=COMPROM
 bit 3    DEBUG=DPMIPHYS
 bit 4    DEBUG=ALLROM
 bit 5    DEBUG=VMS
 bit 6    DEBUG=XMS
 bit 7    DEBUG=I06
 bit 8    DEBUG=VCPI
 bit 9    DEBUG=XDMA
 bit 10    DEBUG=X09
 bit 13    DEBUG=I67
 bit 14    DEBUG=EVM
 bit 15 DEBUG=EMSSAVE or DEBUG=VDS

Bitfields for debugging flags 3:
 bit 10    DEBUG=EPM
 bit 12    DEBUG=ABIOS
 bit 13    DEBUG=XMSPTED
 bit 14    DEBUG=TIME
 bit 15    DEBUG=SCRUB

Bitfields for feature flags 1:
 bit 1    Weitek present
 bit 2    no DPMI services
 bit 3    NODMA
 bit 4    TERSE
 bit 5    NOROM
 bit 6    NOPARITY
 bit 8    NOFLEX (IGNOREFLEXFRAME)
 bit 11    don't create UMBs
 bit 12    don't backfill below video memory (NOLOW)
 bit 13    FRAME= specified
 bit 14    EXT= specified
 bit 15    NOEMS, allow prior expanded memory manager to provide EMS

Bitfields for feature flags 2:
 bit 0    UNSHIFT specified (FORCEA20 disabled)
 bit 1    NOXRAM
 bit 2    NOSCSI specified
 bit 3    SCREEN specified
 bit 4    enabled EISADMA
 bit 5    slow DMA
 bit 6    RESETKEYB specified
 bit 7    ???
 bit 9    TOP384
 bit 11    NOWARMBOOT
 bit 12    USE= specified
 bit 13    ROM= specified

Bitfields for feature flags 3:
 bit 0    Windows3 support enabled
 bit 1    SHADOWROM
 bit 2    don't compress ROM (NOCOMPROM)
 bit 3    ??? (related to PRGREG=)
 bit 4    ??? (related to PRGREG=)
 bit 5    SHADOWRAM
 bit 6    DOS4 specified
 bit 7    NOLOADHIGH
 bit 8    NOPULSE
 bit 11    FORCEA20
 bit 12    DMA buffer enabled
 bit 13 NOSCRUB
 bit 15    NOFRAME

Bitfields for machine type:
 bit 12 Amstrad
 bit 13 Epson
 bit 14 Zenith Data Systems
 bit 15    "ASEM"
 bit 16 NEC
 bit 17    "HPRS" model codes 69h and 6Ah
 bit 18 Dell
 bit 19    "CA"
 bit 20    ITT (Xtra Business Systems/Alcatel)
 bit 21    Toshiba 5100
 bit 22    Olivetti
 bit 23    Quadram Quad386 (BIOS model FEh, submodel A6h)
 bit 24    Tandy???
 bit 25    AST 386
 bit 26    INBOARD, ??? version
 bit 27    INBOARD, ??? version
 bit 28    INBOARD, ??? version
 bit 29    "HPRS"
 bit 30    Compaq 386
 bit 31    JET386

Format of 386MAX control block:
Offset    Size    Description
 00h    WORD    segment of next block (FFFFh if last)
 02h    WORD    segment of previous block (FFFFh if first)
 04h 12 BYTEs    filename
 10h    WORD    resident size in paragraphs
 12h    WORD    environment size???
 14h    WORD    real prsent environment size + 1 (0000h if ENVSAVE used)
 16h  2 BYTEs    ???
 18h    DWORD    initial size or SIZE=n in 386LOAD commandline
 1Ch    DWORD    SIZE=-1 ???
 20h    DWORD    SIZE= ???
 24h    BYTE    PRGREG= if specified, else FFh
 25h    BYTE    ENVREG= if specified, else FFh
 26h    BYTE    FlexFrame (00h not present, 01h present)
 27h  3 BYTEs    ???
 2Ah    BYTE    GROUP= or 00h if not present
 2Bh    BYTE    ???
 2Ch    WORD    PSP

Format of high memory info record:
Offset    Size    Description
 00h    WORD    segment address of memory region
 02h    WORD    size of memory region in paragraphs
 04h    BYTE    type or flags???
        00h if locked out
        02h if EMS page frame
        04h if high RAM
        42h if ROM
 05h    BYTE    ???

Format of ROM shadowing record:
Offset    Size    Description
 00h    WORD    segment of ROM???
 02h    WORD    segment of ROM???
 04h  2 BYTEs    ???
 06h    WORD    size of shadowed ROM in paragraphs
 08h  4 BYTEs    ???

Values for memory type:
 00h    unused by EMS
 01h    DOS
 04h    page frame overlapping ROM???
 80h    high memory
 84h    page frame???
 87h    video ROM???
Note:    the type may be 00h (unused) if the 16K page is split among different
      uses (such as ROM and high RAM)

Call 386MAX API (via OUT DX,AL) with:
    STACK: WORD value for DX
    AH = 01h get high memory information
        ES:DI -> buffer for array of high memory info records
            (see above)
        Return: CX = number of records placed in buffer
    AH = 02h get shadowed ROM info???
        ES:DI -> buffer for array of ROM shadowing records (see above)
        Return: CX = number of records placed in buffer
    AH = 03h get 386MAX state
        ES:DI -> 90-byte buffer for state (see above)
        Return: AH = 00h (successful)
            buffer filled
        Note:    unlike INT 21/AX=4402h"386MAX", this function omits
              the first byte specifying the state buffer version
    AH = 04h get memory types???
        ES:DI -> buffer for memory type info (array of bytes, one per
            16K page) (see above)
        Return:    CX = number of bytes placed in buffer
    AH = 05h get ???
        AL = A20 control (00h enable A20 first, 01h leave unchanged)
        CX = number of 4K pages to report (0000h for default)
        SI = first K to report (rounded down to 4K page)
        ES:DI -> buffer for returned info on ???
        Return: CX = number of 4K pages reported on
            ???
    AH = 06h get memory speed info
        ES:DI -> buffer for memory speed records (see below)
        Return: AH = 00h (successful)
            CX = number of bytes placed in buffer
        Note:    this function can take over a second to execute
    AH = 07h ???
        DX = EMS handle (on stack)
        ???
        Return:    ???
    AH = 08h "EMM2_GOREAL" check whether possible to disable 386MAX
        AL = ??? (00h or nonzero)
        Return: AH = status (00h OK, A4h not possible at this time)
        Note:    if AL=00h, this function always returns success
    AH = 09h toggle ??? flags
        BX = bitmask of bits of ??? flags (word at state+10h) to toggle
        Return: AH = 00h (successful)
        Note:    enables A20 first
    AH = 0Ah toggle ??? flags
        BX = bitmask of bits of ??? (word at state+32h) to toggle
        Return: AH = 00h (successful)
        Notes:    enabled A20 first
            does ??? if bit 3 on after specified bits are toggled
    AH = 0Bh toggle ??? flags
        BX = bitmask of bits of ??? (word at state+34h) to toggle
        Return: AH = 00h (successful)
        Note:    enables A20 first
    AH = 0Ch toggle ??? flags
        BX = bitmask of bits of ??? (word at state+40h) to toggle
        Return: AH = 00h (successful)
        Note:    enables A20 first
    AH = 0Dh specify 386MAX high-memory location
        BX = segment address of high-memory real-mode portion of 386MAX
        CX = current segment of real-mode stub???
        Return: AH = status (00h successful)
            ???
    AH = 0Eh CRT controller register virtualization
        AL = subfunction
            00h allow access to CRTC I/O ports 03B4h/03B5h, 03D4h/03D5h
            01h trap accesses to CRTC I/O ports
    AH = 0Fh reboot system
        Return: never
    AH = 11h get high memory information
        ES:DI -> 96-byte buffer for high memory info
        Return: AH = 00h (successful)
            ES:DI buffer filled
        Notes:    each byte in buffer contains bit flags for a 4K page in
              the A000h-FFFFh region
                bit 0: ???
                bit 1: physical address same as linear address
                bit 2: EMS page frame
                bit 6: ???
            this function can take over a second to execute,
              because it also tests the memory
    AH = 12h ???
        AL = subfunction
            00h ???
            01h ???
        ???
        Return: AH = 00h (successful) if AL=00h or 01h
            AH = 8Fh otherwise
    AH = 13h page protection???
        AL = subfunction
            00h set all ??? 4K pages to read-only???
            01h set all ??? 4K pages to read-write???
        ???
        Return: AH = 00h (successful) if AL=00h or 01h
            AH = 8Fh otherwise
    AH = 14h ???
        ES:DI -> 54-byte buffer for ???
        Return: AH = 00h if successful
            AH = A4h on error
    AH = 15h ???
        ???
        Return: ???
    AH = 16h get 386MAX memory usage screen
        ES:DI -> buffer for memory info display
        CX = size of buffer in bytes
        Return:    ES:DI buffer filled with '$'-terminated string (if
                large enough to hold entire usage screen)
        Note:    the screen is 0303h bytes in v7.00
    AH = 17h Windows 3 startup/termination
        AL = subfunction
            00h Windows3 initializing
            DX (on stack) = Windows startup flags
            DI = Windows version number (major in upper byte)
            ES:BX = 0000h:0000h
            DS:SI = 0000h:0000h
            Return: CX = 0000h if OK for Windows to load
                   <> 0 if Windows should not load
                ES:BX -> startup info structure
                DS:SI -> Virtual86 mode enable/disable callback
            01h Windows3 terminating
            ES:BX -> ???
            DX (on stack) = Windows exit flags
            Return: ???
    AH = 18h QPMS (Qualitas Protected Memory Services)
        AL = subfunction
            00h get QPMS configuration
            Return: BX = starting segment of QPMS memory window
                CX = number of 4K pages reserved for QPMS???
                DX = number of 4K pages in QPMS window???
            01h map QPMS memory page???
            BX = 4K page number within memory reserved for QPMS???
            CL = 4K page number within QPMS memory window???
            02h mark all QPMS memory read-only
            03h mark all QPMS memory read-write
        Return: AH = status (00h,8Ah,8Bh,8Fh)
    AH = 19h get linear address for physical address
        EDX = physical address (low word on stack)
        Return: AH = status
                00h successful
                EDX = linear address at which physical address
                    may be accessed
                8Bh physical address currently not addressable
        Note:    enables A20 first
    AH = 1Ah set page table entry???
        EDX = new page table entry??? (low word on stack)
        ESI = linear address of page???
        Return: AH = status (00h,8Bh)
        Note:    enables A20 first
    AH = 1Bh get ???
        Return: AH = status
            BX = ???
            CX = ???
            EDX = physical address of ???
    AH = 1Ch get original interrupt vector
        AL = interrupt vector (00h-7Fh)
        Return: AH = 00h (successful)
            EDX = original vector before 386MAX loaded (segment in
                high word, offset in low word)
        Note:    no range checking is performed; requests for INTs 80h-
              FFh will return random values
    AH = 1Dh display string???
        SI = ???
        Return: AH = 00h (successful)
            ???
    AH = 1Eh get memory info
        ES:DI -> memory info (see below)
        Return: ???
    AH = 1Fh get DPMI host information
        Return: AX = 0000h if successful
            BX = DPMI flags (see INT 31/AX=0400h)
            CL = CPU type (02h = 80286, 03h = 80386, etc.)
            DX = DPMI ver supported (DH=major, DL=2-digit minor)
            SI = ???
            ES???:DI -> ???
        Note:    NOP if NODPMI switch specified
    AH = 20h (v7.00) ???
        AL = ???
        Return: EDX = ??? for ??? AL
    AH = 21h (v7.00) STACKS support
        AL = 00h get STACKS parameters
        Return: BX = ???
            CX = number of stacks for hardware interrupts
            DX = size of each stack in bytes
            SI = ???
            DI = ???
        AL = 01h set ??? "EMM2_DSTKS"
        EBX = ???
        ECX = ???
        DS = ???
        AL = 02h ???
        BL = ??? (00h-03h)
        ???
    AH = 22h (v7.00)
        AL = 00h ???
        AL = nonzero ???
        ???
    AH = 23h (v7.00) ???
        AL = 00h set ???
        ???
        AL = 01h ???
        ???
        AL = 02h get ???
        CX = size of buffer
        ES:DI -> buffer for ???
        Return: CX = number of bytes actually returned
        AL = 03h set ???
        ES:DI -> buffer containing ASCIZ ???
        AL = 04h get ???
        ES:DI -> buffer for ASCIZ ???
    AH = 24h (v7.00) ???
        AL = 00h get ???
        Return: BX = current state of ??? (0/1)
        AL = 01h set ???
        BX = new state of ??? (0/1)
        AL = other ???
    AH = 25h (v7.00) ???
    AH = 26h (v7.00) ???
        Return: BX = ???
            CX = ???
    AH = 27h (v7.00) ???
        AL = 00h get ???
        Return: BX = ???
        AL = 01h ???
        BX = ???
        ES??? = ???
        AL = 02h ???
        ???
        AL = 03h ???
        CX = ???
        DX = ???
        ES??? = ???
        Return: ???
    AH = 28h (v7.00) get ???
        Return: CX = ???
            DX = ???
    AH = 29h (v7.00) get ???
        Return: AX = ???
    AH = 40h-5Dh EMS services (see INT 67/AH=40h etc)
    AH = DEh VCPI services (see INT 67/AX=DE00h etc)
Return: AH = status (as for EMS INT 67 calls)
        00h successful
        80h internal error
        81h hardware malfunction
        83h invalid handle
        84h    undefined function
        8Ah invalid logical page nuber
        8Bh illegal physical page number
        8Fh undefined subfunction
        A4h access denied
        etc.
    STACK popped (value placed in DX if no specific return value for DX)

Format of memory speed record:
Offset    Size    Description
 00h    DWORD    page table entry for 4K page
 04h    WORD    number of microticks (840ns units) required for REP LODSD of
        entire 4K page

Format of memory info [array]:
Offset    Size    Description
 00h    DWORD    ???
 04h    DWORD    ???
 08h  2 BYTEs    ???
 0Ah    BYTE    type??? (03h = conventional???)
 0Bh    BYTE    ???
--------V-214402-----------------------------
INT 21 - PGS1600.DEV - IOCTL - GET CONFIGURATION INFO
    AX = 4402h
    BX = file handle for device "PGS1600$"
    CX = 0018h (size of buffer)
    DS:DX -> configuration buffer (see below)
Return: CF clear if successful
        buffer filled
        AX = number of bytes actually copied
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: PGS1600.DEV is a device driver for the Cornerstone Technology PG1600
      display adapter, which provides a 1600x1200 monochrome display as
      well as one of two emulations, MDA or CGA.
SeeAlso: AX=4403h"PGS1600"

Format of configuration information:
Offset    Size    Description
 00h    WORD    version (high byte = major, low byte = minor)
 02h    WORD    board initialisation mode
 04h    WORD    board I/O address
        03D0h CGA emulation
        03B0h MDA emulation
        0390h no emulation
        0350h no emulation, alternate
 06h    WORD    emulation buffer segment
        B800h    CGA emulation
        B000h    MDA emulation
        0000h    no emulation
 08h    WORD    PG1600 graphics buffer segment
 0Ah    WORD    number of bytes between consecutive graphic rows
 0Ch    WORD    horizontal pixel size
 0Eh    WORD    vertical pixel size
 10h    WORD    horizontal dots per inch
 12h    WORD    vertical dots per inch
 14h    WORD    graphics buffer bits per pixel
 16h    WORD    monitor bits per pixel
--------N-214402-----------------------------
INT 21 - PC/TCP IPCUST.SYS - RESET CONFIGURATION DATA READ POINTER
    AX = 4402h
    BX = file handle referencing device "$IPCUST"
    CX, DS:DX ignored
Return: CF clear if successful
        AX destroyed
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Notes:    there are a total of 378h bytes of configuration data for IPCUST.SYS
      version 2.05.     If less than the entire data is read or written,
      the next read/write continues where the previous one ended; this
      call and AX=4403h both reset the location at which the next
      operation starts to zero
    v2.1+ uses a new configuration method, but allows the installation
      of IPCUST.SYS for backward compatibility with other software which
      must read the PC/TCP configuration
SeeAlso: AH=3Fh"IPCUST",AH=40h"IPCUST",AX=4403h"IPCUST"
--------N-214402-----------------------------
INT 21 - WORKGRP.SYS - GET API ENTRY POINT
    AX = 4402h
    BX = file handle for device "NET$HLP$"
    CX = 0008h
    DS:DX -> buffer for entry point record
Return: CF clear if successful
        AX = number of bytes actually read
    CF set on error
        AX = error code
Program: WORKGRP.SYS is distributed with MS-DOS 6.0 to permit communication
      with PCs running Windows for Workgroups or LAN Manager
SeeAlso: AH=3Fh"WORKGRP.SYS"

Format of entry point record:
Offset    Size    Description
 00h    WORD    3633h  \ signature???
 02h    WORD    EF6Fh  /
 04h    DWORD    address of entry point
Note:    first four bytes of buffer must be 6Fh E9h 33h 36h on entry when using
      IOCTL rather than READ to get the entry point record

Call WORKGRP entry point with:
    STACK:    WORD    function number (0000h-0009h)
Return: STACK unchanged

Call WORKGRP function 00h with:
    STACK:    WORD    0000h (function "get ???")
Return: DX:AX -> data table

Call WORKGRP function 01h with:
    STACK:    WORD    0001h (function "hook ???")
Return: STACK:    DWORD    pointer to ???
        WORD    0001h (function number)

Call WORKGRP function 02h with:
    STACK:    WORD    0002h (function "unhook ???")
    ???
Return: ???

Call WORKGRP function 03h with:
    STACK:    WORD    0003h (function "reenable printer port")
        WORD    LPT port number
Return: ???

Call WORKGRP function 04h with:
    STACK:    WORD    0004h (function "disable printer port")
        WORD    LPT port number
Return: ???

Call WORKGRP function 05h with:
    STACK:    WORD    0005h (function "???")
        ???
Return: ???

Call WORKGRP function 06h with:
    STACK:    WORD    0006h (function "???")
Return: STACK unchanged
    AX = 0000h
    DX = 0000h

Call WORKGRP functions 07h-09h with:
    STACK:    WORD    0007h-0009h (NOP functions)
Return: STACK unchanged
    AX = 0001h
    DX = 0000h
--------N-214402-----------------------------
INT 21 - 10NET v5.0 - 10BEUI.DOS - API
    AX = 4402h
    BX = file handle referencing device "10BEUI$"
    DS:DX -> parameter record (see below)
    CX ignored
Return: CF clear if successful
        AX destroyed
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h"10MEMMGR",INT 6F/AH=00h"10NET"

Format of parameter record:
Offset    Size    Description
 00h    WORD    000Ah (function number???)
 02h    WORD    ???
 04h    DWORD    pointer to buffer for ???
 08h  4 BYTEs    ???
 0Ch    WORD    transfer size
--------N-214402-----------------------------
INT 21 - 10NET v5.0 - 10MEMMGR.SYS - API
    AX = 4402h
    BX = file handle referencing device "MEMMGR0$"
    DS:DX -> 6-byte buffer for interface info (see below)
    CX ignored
Return: CF clear if successful
        AX destroyed
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h"10BEUI",INT 6F/AH=00h"10NET"

Format of interface info:
Offset    Size    Description
 00h    DWORD    address of entry point (see below)
 04h    WORD    version (0500h for v5.00)

Call entry point with:
    AL = 01h ???
        BX = ???
        Return: CF clear if successful
            CF set on error
            AX = error code
    AL = 02h ???
        ???
    AL = 03h ???
        ???
    AL = 04h set/restore memory allocation strategy
        BX = subfunction
        0000h set strategy
        0001h restore strategy
        Return: CF clear if successful
            CF set on error (if function disabled)
            various registers destroyed
    AL = other
        Return: CF set
            AX = 0000h
            BL = 01h
--------m-214402SF00-------------------------
INT 21 U - Memory Managers - GET API ENTRY POINT
    AX = 4402h subfn 00h
    BX = file handle for device "EMMXXXX0"
    CX = 0006h (size of buffer in bytes)
    DS:DX -> buffer for API entry point record (see below)
        first byte must be 00h on entry
Return: CF clear if successful
        buffer filled (see INT 67/AH=3Fh function 1B00h)
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Notes:    this function is supported by Microsoft EMM386.EXE v4.45+ and
      CEMM v5.10+, and is intended for use by MS Windows as it starts up
    if no other program has hooked INT 67, an alternate installation
      check for CEMM is testing for the string
      "COMPAQ EXPANDED MEMORY MANAGER 386" at offset 14h in the INT 67
      handler's segment; if present, the word at offset 12h contains the
      offset of the API entry point
SeeAlso: AX=4402h/SF=01h,AX=4402h/SF=02h,AX=4402h"EMM386",INT 67/AH=3Fh

Format of API entry point record:
Offset    Size    Description
 00h    WORD    ??? (0022h for CEMM 5.11, 0025h for MS EMM386 v4.45)
 02h    DWORD    manager's private API entry point (see below,INT 67/AX=FFA5h)

Call CEMM v5.10+ entry point with:
    AH = 00h get memory manager's state
        Return: AH = state
            bit 0: turned OFF
            bit 1: AUTO mode enabled
    AH = 01h set memory manager's state
        AL = new state (00h ON, 01h OFF, 02h AUTO)
        Return: CF clear if successful
            CF set on error
    AH = 02h Weitek coprocessor support
        AL = subfunction
        00h get Weitek support state
            Return: AL = status
                bit 0: Weitek coprocessor is present
                bit 1: Weitek support is enabled
        01h turn on Weitek support
        02h turn off Weitek support
        Return: CF clear if successful
            CF set on error
            AH = error code (01h invalid subfunc, 02h no Weitek)
    AH = 05h get statistics
        ???
    AH > 06h
        Return: CF set
            AH = 01h (invalid function)
Notes:    AH=03h,04h,06h are NOPs which return CF clear, presumably for backwards
      compatibility with earlier versions of CEMM
    in v5.11, AH=05h merely prints an error message (using INT 21/AH=09h)
      stating that a different version of CEMM is installed and it is
      therefore not possible to display the statistics
--------m-214402SF01-------------------------
INT 21 U - Memory Managers - GET EMM IMPORT STRUCTURE ADDRESS
    AX = 4402h subfn 01h
    BX = file handle for device "EMMXXXX0"
    CX = 0006h (size of buffer in bytes)
    DS:DX -> buffer for EMM import structure record (see below)
        first byte must be 01h on entry
Return: CF clear if successful
        buffer filled (see INT 67/AH=3Fh function 1B00h)
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Notes:    this function is supported by Microsoft EMM386.EXE v4.45+,
      QEMM-386 v6+, and CEMM v5.10+, and is intended for use by MS Windows
      as it starts up
    for QEMM-386, this call always returns an error if Windows3 support
      has been disabled with the NW3 switch
SeeAlso: AX=4402h/SF=00h,AX=4402h"EMM386",INT 2F/AX=D201h/BX=5145h
SeeAlso: INT 67/AH=3Fh

Format of EMM import structure record:
Offset    Size    Description
 00h    DWORD    physical address of EMM import structure
 04h    BYTE    EMM import structure major version
 05h    BYTE    EMM import structure minor version
--------m-214402SF02-------------------------
INT 21 U - Memory Managers - GET MEMORY MANAGER VERSION
    AX = 4402h subfn 02h
    BX = file handle for device "EMMXXXX0"
    CX = 0002h (size of buffer in bytes)
    DS:DX -> buffer for memory manager version (see below)
        first byte must be 02h on entry
Return: CF clear if successful
        buffer filled
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    this function is supported by Microsoft EMM386.EXE v4.45+ and
      CEMM v5.10+, and is intended for use by MS Windows as it starts up
SeeAlso: AX=4402h/SF=00h,AX=4402h"EMM386",INT 67/AH=3Fh

Format of memory manager version:
Offset    Size    Description
 00h    BYTE    major version
 01h    BYTE    minor version (binary)
--------m-214402-----------------------------
INT 21 U - Microsoft EMM386.EXE v4.45 - GET MEMORY MANAGER INFORMATION
    AX = 4402h
    BX = file handle for device "EMMXXXX0"
    CX = size of buffer in bytes (varies, see below)
    DS:DX -> buffer for returned data (see below)
        first byte must be set on entry to indicate desired data
Return: CF clear if successful
        buffer filled
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Notes:    an error is returned if the number of bytes to be read does not match
      the number of bytes returned for the specified data item
    this function is part of the interface which allows MS Windows to
      cooperate with memory managers
SeeAlso: AX=4402h/SF=00h,AX=4402h/SF=01h,AX=4402h/SF=02h,INT 67/AX=FFA5h

Format of data buffer:
Offset    Size    Description
 00h    BYTE    (call) function
        03h get ???
        04h get ???
---function 03h---
 00h    WORD    ???
 02h    WORD    ???
---function 04h---
 00h    WORD    segment of UMB containing EMM386 code/data
 02h    WORD    number of paragraphs of EMM386 code/data in UMB
 04h    WORD    ???
--------V-214402-----------------------------
INT 21 - Compaq AG1024.SYS - RGDI - GET DRIVER LOCATION
    AX = 4402h
    BX = file handle for device "$$$$RGDI"
    CX = 0006h (size of returned data)
    DS:DX -> location record (see below)
Return: CF clear if successful
        buffer filled
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: AG1024.SYS is a device driver for the Advanced Graphics 1024 adapter
SeeAlso: AX=4403h"RGDI"

Format of location record:
Offset    Size    Description
 00h    WORD    signature 55AAh
 02h    WORD    segment of ???
 04h    WORD    segment of device driver's code
--------N-214402-----------------------------
INT 21 - FTPSOFT.DOS v3.1 - GET ???
    AX = 4402h
    BX = file handle for device "FTPSOFT$"
    CX = size of buffer
    DS:DX -> buffer for data (see below)
Return: CF clear if successful
        buffer filled
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: FTPSOFT.DOS is a device driver for Protocol Manager support from
       FTP Software, Inc.
SeeAlso: AH=3Fh"PC/TCP",AX=4402h"NDIS"

Format of data:
Offset    Size    Description
 00h    WORD    (call) BA98h (if different, no data returned)
 02h    DWORD    -> NDIS common characteristics table (see AX=4402h"NDIS")
 06h    DWORD    (call) -> new dispatch table (see AX=4402h"NDIS")
 0Ah    DWORD    -> 28-byte buffer for ??? data
 0Eh    DWORD    ???
 12h    DWORD    -> FAR function to reset dispatch jump table to defaults
 16h    BYTE    ???
Note:    the addresses in the new dispatch table are copied into an internal
      jump table which may be reset by calling the function pointed at by
      offset 12h
----------214402-----------------------------
INT 21 U - PenDOS PENDEV.SYS - GET ENTRY POINTS
    AX = 4402h
    BX = file handle for device "$$PENDOS" or "$$PD_REG"
    CX = size of buffer (4 for $$PENDOS and a 4,8,12, or 16 for $$PD_REG)
    DS:DX -> buffer for entry point record (see below)
Return: CF clear if successful
        buffer filled
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: A limited version of PenDOS by Communication Intelligence Corporation,
      which provides pen capability to keyboard-based programs, is bundled
      with IBM DOS 6.1
SeeAlso: AX=4403h"PENDEV.SYS"

Format of entry point record:
Offset    Size    Description
 00h    DWORD    -> array of jumps
 04h    WORD    offset of function to retrieve entry point
 06h  2 BYTEs    signature "Pe"
 08h    WORD    offset of function to set entry point
 0Ah  2 BYTEs    signature "nD"
 0Ch    WORD    offset of function to clear entry point
 0Eh    WORD    signature "OS"

Call function to retrieve entry point with:
    AX = index of entry point (0-9)
Return: CF clear if successful
        DX:AX -> desired entry point
    CF set on error (AX out of range)

Call function to set entry point with:
    AX = index of entry point (0-9)
    DX:SI -> new handler
Return: CF clear if successful
    CF set on error (AX out of range)

Call function to clear entry point with:
    AX = index of entry point (0-9)
Return: CF clear if successful
    CF set on error (AX out of range)
Note:    resets the jump at the specified entry point to its default target,
      which simply returns
--------D-214403-----------------------------
INT 21 - DOS 2+ - IOCTL - WRITE TO CHARACTER DEVICE CONTROL CHANNEL
    AX = 4403h
    BX = file handle referencing character device
    CX = number of bytes to write
    DS:DX -> data to write
Return: CF clear if successful
        AX = number of bytes actually written
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Notes:    format of data is driver-specific (see below for some specific cases)
    if the file handle refers to "4DOSSTAK", the 4DOS (v2.x-3.03)
      KEYSTACK.SYS driver will push the specified characters on the
      keyboard stack; similarly for "NDOSSTAK", the NDOS KEYSTACK.SYS
      driver will push the characters onto the keyboard stack
SeeAlso: AX=4400h,AX=4402h,AX=4405h,INT 2F/AX=122Bh,INT 2F/AX=D44Dh
SeeAlso: INT 2F/AX=D44Fh
--------c-214403-----------------------------
INT 21 - SMARTDRV.SYS - IOCTL - CACHE CONTROL
    AX = 4403h
    BX = handle for device "SMARTAAR"
    CX = number of bytes to write
    DS:DX -> SMARTDRV control block (see below)
Return: CF clear if successful
        AX = number of bytes actually written
           = 0000h if control block too small for given command
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h"SMARTDRV",INT 2F/AX=4A10h/BX=0000h

Format of SMARTDRV control block:
Offset    Size    Description
 00h    BYTE    function code
        00h flush cache
        01h flush and discard cache
        02h disable caching (flushes and discards cache first)
        03h enable caching
        04h control write caching
        05h set flushing tick count
        06h lock cache contents
        07h unlock cache contents
        08h set flush-on-reboot flag
        09h unused
        0Ah control full-track caching
        0Bh reduce cache size
        0Ch increase cache size
        0Dh set INT 13 chain address
---function 04h---
 01h    BYTE    write caching control action
        00h turn off write-through
        01h turn on write-through
        02h turn off write buffering (also flushes cache)
        03h turn on write buffering (also flushes cache)
---function 05h---
 01h    WORD    number of timer ticks between cache flushes
---function 08h---
 01h    BYTE    new flush-on-reboot flag (00h off, 01h on)
---function 0Ah---
 01h    BYTE    full-track writes are
        00h not cached
        01h cached
---functions 0Bh,0Ch---
 01h    WORD    number of 16K pages by which to increase/reduce cache size
---function 0Dh---
 01h    DWORD    new address to which to chain on INT 13
Note:    the previous address is not preserved
--------d-214403-----------------------------
INT 21 - CD-ROM device driver - IOCTL OUTPUT
    AX = 4403h
    BX = file handle referencing character device for CD-ROM driver
    CX = number of bytes to write
    DS:DX -> control block (see below)
Return: CF clear if successful
        AX = number of bytes actually written
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h"CD-ROM",INT 2F/AX=0802h

Format of control block:
Offset    Size    Description
 00h    BYTE    function code
        00h eject disk
        01h lock/unlock door
        02h reset drive
        03h control audio channel
        04h write device control string
        05h close tray
---functions 00h,02h,05h---
 no further fields
---function 01h---
 01h    BYTE    lock function
        00h unlock door
        01h lock door
---function 03h---
 01h    BYTE    input channel (0-3) for output channel 0
 02h    BYTE    volume for output channel 0
 03h    BYTE    input channel (0-3) for output channel 1
 04h    BYTE    volume for output channel 1
 05h    BYTE    input channel (0-3) for output channel 2
 06h    BYTE    volume for output channel 2
 07h    BYTE    input channel (0-3) for output channel 3
 08h    BYTE    volume for output channel 3
Note:    output channels 0 and 1 are left and right, 2 and 3 are left prime and
      right prime; a volume of 00h is off
---function 04h---
 01h  N BYTEs    bytes to send directly to the CD-ROM drive without
        interpretation
--------d-214403-----------------------------
INT 21 - Brian Antoine Seagate ST-01 SCSI.SYS - IOCTL - EXECUTE COMMANDS
    AX = 4403h
    BX = handle for device "SCSITAPE"
    CX = number of bytes to write
    DS:DX -> SCSITAPE control block (see below)
Return: CF clear if successful
        AX = number of bytes actually written
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4405h"ST-01",INT 78/AH=10h

Format of SCSITAPE control block:
Offset    Size    Description
 00h    WORD    command type
        'F' Format (argument 1 = interleave, argument 2 = format type)
        'E' Erase
        'R' Rewind
        'L' Load
        'N' No Load
        'S' Space (argument 1 = count, argument 2 = type)
        'M' File Mark (argument 1 = count)
        'A' Reassign
 02h    WORD    argument 1
 04h    WORD    argument 2
 06h    WORD    segment of command buffer
 08h    WORD    offset of command buffer
 0Ah    WORD    length of command buffer
--------E-214403-----------------------------
INT 21 U - AI Architects - OS/x86??? - API
    AX = 4403h
    BX = handle for device "AIA_OS"
    CX = number of bytes to write (ignored)
    DS:DX -> 12-byte buffer, first byte is command:
            81h installation check
            82h get API entry point
            84h uninstall
Return: CF clear if successful
        AX = number of bytes actually written
    CF set on error
        AX = error code (01h,05h,06h,0Ch,0Dh) (see AH=59h)
Notes:    these functions are only available if the DOS extender was loaded as a
      device driver in CONFIG.SYS
    called by TKERNEL (a licensed version of AI Architects/Ergo OS/x86)
SeeAlso: INT 2F/AX=FBA1h/BX=0081h,INT 2F/AX=FBA1h/BX=0082h
Index:    installation check;OS/x86|entry point;OS/x86|uninstall;OS/x86

Format of buffer on return:
Offset    Size    Description
 00h  4 BYTEs    signature "IABH"
---if func 81h---
 (no additional fields)
---if func 82h---
 04h    DWORD    pointer to API entry point (see INT 2F/AX=FBA1h/BX=0082h)
---if func 84h---
 04h    WORD    success indicator
 06h    WORD    segment of ???
 08h    WORD    segment of ??? memory block to free if nonzero
 0Ah    WORD    segment of ??? memory block to free if nonzero
--------V-214403-----------------------------
INT 21 - PGS1600.DEV - IOCTL - SET CONFIGURATION???
    AX = 4403h
    BX = file handle for device "PGS1600$"
    CX = 0018h (size of buffer)
    DS:DX -> configuration buffer (see AX=4402h"PGS1600")
Return: CF clear if successful
        AX = number of bytes actually written
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: PGS1600.DEV is a device driver for the Cornerstone Technology PG1600
      display adapter, which provides a 1600x1200 monochrome display as
      well as one of two emulations, MDA or CGA.
SeeAlso: AX=4402h"PGS1600"
--------N-214403-----------------------------
INT 21 - PC/TCP IPCUST.SYS - RESET CONFIGURATION DATA READ POINTER
    AX = 4403h
    BX = file handle referencing device "$IPCUST"
    CX, DS:DX ignored
Return: CF clear if successful
        AX destroyed
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Notes:    there are a total of 378h bytes of configuration data for IPCUST.SYS
      version 2.05.     If less than the entire data is read or written,
      the next read/write continues where the previous one ended; this
      call and AX=4402h both reset the location at which the next
      operation starts to zero
    v2.1+ uses a new configuration method, but allows the installation
      of IPCUST.SYS for backward compatibility with other software which
      must read the PC/TCP configuration
SeeAlso: AH=3Fh"IPCUST",AH=40h"IPCUST",AX=4402h"IPCUST"
--------V-214403-----------------------------
INT 21 - Compaq AG1024.SYS - CPQ_MGES - IOCTL OUTPUT
    AX = 4403h
    BX = file handle referencing device "CPQ_MGES"
    DS:DX -> request packet (see below)
    CX ignored
Return: CF clear if successful
        AX destroyed
        data buffer filled (if applicable)
        first word of request packet set to number of bytes of data
          available (amount returned is smaller of this and requested
          amount)
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: AG1024.SYS is a device driver for the Advanced Graphics 1024 adapter
SeeAlso: AX=4403h"RGDI"

Format of request packet:
Offset    Size    Description
 00h    WORD    function
        0000h get ??? (26h bytes)
        0001h get ??? (36h bytes)
        0002h set ??? (same as returned by function 0001h)
        0003h get ??? (6 bytes)
        0004h get ???
        0005h get ???
        0006h get ??? (10h bytes)
        0007h set ??? (same as returned by function 0006h)
---functions 00h-03h,06h,07h---
 02h    WORD    size of data buffer
 04h    DWORD    -> buffer for function's data
 ---functions 04h,05h---
 02h    WORD    ???
 04h    WORD    size of data buffer
 06h    DWORD    -> buffer to receive data
--------V-214403-----------------------------
INT 21 - Compaq AG1024.SYS - RGDI - IOCTL OUTPUT
    AX = 4403h
    BX = file handle referencing device "$$$$RGDI"
    DS:DX -> request packet (see below)
    CX ignored
Return: CF clear if successful
        AX destroyed
        data buffer filled (if applicable)
        first word of request packet set to number of bytes of data
          available (amount returned is smaller of this and requested
          amount)
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: AG1024.SYS is a device driver for the Advanced Graphics 1024 adapter
SeeAlso: AX=4402h"RGDI",AX=4403h"CPQ_MGES"

Format of request packet:
Offset    Size    Description
 00h    WORD    function
        0000h get entry points
        0001h get ???
 02h    DWORD    address of buffer for returned data
----------214403SF01-------------------------
INT 21 U - Qualitas 386MAX v6.01+ - TURN 386MAX OFF
    AX = 4403h subfn 01h
    BX = handle for device "386MAX$$"
    DS:DX -> BYTE 01h
    CX ignored
Return: DS:DX -> BYTE status (00h = successful)
    CF clear if successful
        AX destroyed
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    this function will fail if any EMS or UMBs are in use
SeeAlso: AX=4403h/SF=02h,AX=4403h/SF=03h,AX=4403h/SF=05h
----------214403SF02-------------------------
INT 21 U - Qualitas 386MAX v6.01+ - TURN 386MAX ON
    AX = 4403h subfn 02h
    BX = handle for device "386MAX$$"
    DS:DX -> BYTE 02h
    CX ignored
Return: DS:DX -> BYTE status (00h = successful)
    CF clear if successful
        AX destroyed
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4403h/SF=01h,AX=4403h/SF=03h,AX=4403h/SF=05h
--------m-214403SF03-------------------------
INT 21 U - Qualitas 386MAX v6.01+ - SET STATE
    AX = 4403h subfn 03h
    BX = handle for device "386MAX$$"
    CX = number of bytes to copy (up to size of state buffer)
    DS:DX -> BYTE 03h followed by state buffer (see AX=4402h"386MAX")
Return: CF clear if successful
        AX = number of bytes actually written
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    the first byte of the buffer must be either 01h, 02h, or 03h
      (specifying the version of the state record) and the buffer must
      contain CX bytes AFTER the initial byte
SeeAlso: AX=4402h"386MAX"
----------214403SF05-------------------------
INT 21 U - Qualitas 386MAX v7.00+ - LIMIT AUTOMATIC ACTIVATION TO STD EMS CALLS
    AX = 4403h subfn 05h
    BX = handle for device "386MAX$$"
    DS:DX -> BYTE 05h
    CX ignored
Return: CF clear if successful
        AX destroyed
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Desc:    specifies that 386MAX will only shift from AUTO to ON mode on standard
      EMS calls INT 67/AH=40h-5Dh
SeeAlso: AX=4403h/SF=02h,AX=4403h/SF=03h,AX=4403h/SF=06h
----------214403SF06-------------------------
INT 21 U - Qualitas 386MAX v7.00+ - ALLOW AUTOMATIC ACTIVATION ON ANY INT 67
    AX = 4403h subfn 06h
    BX = handle for device "386MAX$$"
    DS:DX -> BYTE 06h
    CX ignored
Return: CF clear if successful
        AX destroyed
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Desc:    specified that 386MAX should shift from AUTO to ON mode on any INT 67
      call other than INT 67/AH=3Fh
SeeAlso: AX=4403h/SF=01h,AX=4403h/SF=03h,AX=4403h/SF=05h
----------214403-----------------------------
INT 21 U - PenDOS PENDEV.SYS - ???
    AX = 4403h
    BX = file handle for device "$$PENDOS" or "$$PD_REG"
    CX = size of buffer
    DS:DX -> buffer containing ???
Return: CF clear if successful
        buffer filled
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: A limited version of PenDOS by Communication Intelligence Corporation,
      which provides pen capability to keyboard-based programs, is bundled
      with IBM DOS 6.1
Note:    this call sets the WORD at offset 1Ah into the device driver request
      header used to call the driver to 0000h.
SeeAlso: AX=4402h"PENDEV.SYS"
--------D-214404-----------------------------
INT 21 - DOS 2+ - IOCTL - READ FROM BLOCK DEVICE CONTROL CHANNEL
    AX = 4404h
    BL = drive number (00h = default, 01h = A:, etc.)
    CX = number of bytes to read
    DS:DX -> buffer
Return: CF clear if successful
        AX = number of bytes actually read
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    format of data is driver-specific
SeeAlso: AX=4402h,AX=4405h,INT 2F/AX=122Bh
--------d-214404-----------------------------
INT 21 - Stacker - GET DEVICE DRIVER ADDRESS AND SET VOLUME NUMBER
    AX = 4404h
    BL = drive number (00h = default, 01h = A:, etc.)
    CX = 0004h
    DS:DX -> DWORD buffer to receive device driver address
Note:    In addition to returning the address of the Stacker device driver,
      this call also sets the volume number at offset 3Eh in the device
      driver (see INT 25/AX=CDCDh)
SeeAlso: INT 25/AX=CDCDh
--------d-214404-----------------------------
INT 21 - Stacker - GET STACVOL FILE SECTORS
    AX = 4404h
    BL = drive number (0 is current drive)
    CX = byte count (i.e., 200h = 1 sector)
    DS:DX -> buffer (see below)
Return: Data Buffer contains the number of sectors requested from the
      STACVOL physical file for the drive specified.

Format of stacker buffer:
Offset    Size    Description
 00h    WORD    01CDh
 02h    WORD    sector count
 04h    DWORD    number of starting sector
 08h    DWORD    far pointer to Data Buffer
--------d-214404-----------------------------
INT 21 - DUBLDISK.SYS v2.6 - GET INFO
    AX = 4404h
    BL = drive number of DoubleDisk drive (00h = default, 01h = A:, etc.)
    CX = number of bytes (000Ah-0014h, call ignored otherwise)
    DS:DX -> data record (see below)
Return: CF clear if successful
        AX = number of bytes read
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: DUBLDISK.SYS is the device driver portion of DoubleDisk, a disk
      expander by Vertisoft Systems, Inc.
Note:    the installation check consists of scanning memory for the signature
      "FAT 2.6  byte:", which is immediately followed by a data table
SeeAlso: AX=440Dh
Index:    installation check;DUBLDISK.SYS

Format of data record:
Offset    Size    Description
 00h    WORD    (call) signature 4444h
 02h    BYTE    (call) function
            00h ???
            01h ???
---function 00h---
 02h    BYTE    (return) ???
 03h    BYTE    (return) ???
---function 01h---
 02h    WORD    (return) 4444h
 04h    WORD    allocation unit size???
 06h    WORD    ???
 08h    WORD    ???
 0Ah    BYTE    ???

Format of signature data table:
Offset    Size    Description
 00h  5 BYTEs    ???
 05h    BYTE    first drive number
 06h    BYTE    number of drives
 07h    ???
--------d-214404-----------------------------
INT 21 - DBLSPACE.BIN - IOCTL - FLUSH OR INVALIDATE INTERNAL CACHES
    AX = 4404h
    BL = drive number (00h = default, 01h = A:, etc)
    CX = 000Ah (size of DSPACKET structure)
    DS:DX -> DSPACKET structure (see below)
Return: CF clear if IOCTL successful -- check DSPACKET for actual status
        AX = number of bytes actually transferred
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4405h"DBLSPACE",INT 2F/AX=4A11h/BX=0000h

Format of DSPACKET structure:
Offset    Size    Description
 00h    WORD    signature 444Dh ("DM")
 02h    BYTE    command code
        46h ('F') flush internal caches
        49h ('I') flush and invalidate internal caches
 03h    WORD    result code
        (return) 4F4Bh ("OK") if successful, else unchanged
 05h  5 BYTEs    padding
--------d-214404-----------------------------
INT 21 U - xDISK v3.31 - CONFIGURE
    AX = 4404h
    BL = drive number (00h = default, 01h = A:, etc)
    CX = 0047h (length of version string)
    DS:DX -> 79-byte buffer for version string and ???
    DS:0081h = commandline containing new switches for driver
Return: CF clear if successful
        AX = number of bytes actually transferred
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: xDISK is a shareware resizeable EMS RAMdisk by FM de Monasterio
SeeAlso: AX=4405h"xDISK",INT 2F/AH=DDh"xDISK"
----------214404-----------------------------
INT 21 - COMBI-disk v1.13 - GET DATA RECORD
    AX = 4404h
    BL = drive number (00h = default, 01h = A:, etc)
    CX =  (length of data packet)
    DS:DX -> buffer for data packet (see below)
Return: CF clear if successful
        AX = number of bytes actually transferred
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: COMBI-disk is a shareware combination cache and RAMdisk sharing a
      single pool of memory by Vadim V. Vlasov
Note:    the installation check consists of scanning the valid drives for one
      which returns a correctly-sized data packet with the proper
      signature in the first field
SeeAlso: AX=4405h"COMBI"
Index:    installation check;COMBI-disk

Format of data packet:
Offset    Size    Description
 00h  6 BYTEs    ASCIZ signature "COMBI"
 06h    WORD    version (high byte = major, low = decimal minor version)
 08h    BYTE    current options (see below)
 09h    BYTE    sectors per allocation block
 0Ah    WORD    maximum buffer in KB
 0Ch    WORD    current buffer in KB (less than max if XMS memory being lent)
 0Eh    WORD    total number of allocation blocks
 10h    WORD    current number of allocation blocks
 12h    WORD    number of blocks being used by RAM disk
 14h    WORD    number of blocks being used by cache or unused
 16h    WORD    number of dirty cache blocks
 18h    WORD    number of blocks which could not be written out due to errors
 1Ah    WORD    total number of read requests
 1Ch    WORD    total number of sectors read
 1Eh    WORD    number of BIOS read requests (cache misses)
 20h    WORD    number of sectors read via BIOS (cache misses)
 22h    WORD    total number of write requests
 24h    WORD    total number of sectors written
 26h    WORD    number of BIOS write requests
 28h    WORD    number of sectors written via BIOS
 2Ah    WORD    number of RAM disk read requests
 2Ch    WORD    number of sectors read from RAM disk
 2Eh    WORD    number of RAM disk write requests
 30h    WORD    number of sectors written to RAM disk
--------D-214405-----------------------------
INT 21 - DOS 2+ - IOCTL - WRITE TO BLOCK DEVICE CONTROL CHANNEL
    AX = 4405h
    BL = drive number (00h = default, 01h = A:, etc)
    CX = number of bytes to write
    DS:DX -> data to write
Return: CF clear if successful
        AX = number of bytes actually written
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    format of data is driver-specific
SeeAlso: AX=4403h,AX=4404h,INT 2F/AX=122Bh
--------d-214405-----------------------------
INT 21 - Brian Antoine Seagate ST-01 SCSI.SYS - IOCTL - EXECUTE COMMANDS
    AX = 4405h
    BX = drive number (00h = default, 01h = A:, etc)
    CX = number of bytes to write
    DS:DX -> SCSIDISK control block (see AX=4403h"ST-01")
Return: CF clear if successful
        AX = number of bytes actually written
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4403h"ST-01"
--------d-214405-----------------------------
INT 21 U - DBLSPACE.BIN - IOCTL - FLUSH OR INVALIDATE INTERNAL CACHES
    AX = 4405h
    BL = drive number (00h = default, 01h = A:, etc)
    CX = 000Ah (size of DSPACKET structure)
    DS:DX -> DSPACKET structure (see below)
Return: CF clear if IOCTL successful -- check DSPACKET for actual status
        AX = number of bytes actually transferred
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    this call is identical to the documented AX=4404h
SeeAlso: AX=4404h"DBLSPACE",INT 2F/AX=4A11h/BX=0000h

Format of DSPACKET structure:
Offset    Size    Description
 00h    WORD    signature 444Dh ("DM")
 02h    BYTE    command code
        46h ('F') flush internal caches
        49h ('I') flush and invalidate internal caches
 03h    WORD    result code
        (return) 4F4Bh ("OK") if successful, else unchanged
 05h  5 BYTEs    padding
--------d-214405-----------------------------
INT 21 U - xDISK v3.31 - ???
    AX = 4405h
    BL = drive number (00h = default, 01h = A:, etc)
    CX = number of bytes to write
    DS:DX -> buffer containing version string
    ???
Return: CF clear if successful
        AX = number of bytes actually transferred
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Program: xDISK is a shareware resizeable EMS RAMdisk by FM de Monasterio
SeeAlso: AX=4404h"xDISK",INT 2F/AH=DDh"xDISK"
--------d-214405-----------------------------
INT 21 - COMBI-disk v1.13 - CONTROL COMBI-disk
    AX = 4405h
    BL = drive number (00h = default, 01h = A:, etc) for RAM disk
    CX = number of bytes to write
    DS:DX -> buffer containing command packet (see below)
Return: CF clear if successful
        AX = number of bytes actually transferred
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4404h"COMBI"

Format of command packet:
Offset    Size    Description
 00h    WORD    version
 02h    BYTE    command code
        80h flush cache
        81h change options byte
        82h shrink memory
        83h expand memory
        84h get dirty block information
        85h reset write errors
        86h reset counters
---command code 81h---
 03h    BYTE    new options byte (see below)
---command code 82h---
 03h    WORD    number of KB to release
---command code 83h---
 03h    WORD    number of KB to expand
---command code 84h---
 03h    DWORD    -> buffer for block info (see below)
---command code 85h---
 03h    DWORD    block ID
---command code 86h---
 03h    BYTE    which counters to reset
        bit 0: hard disk read counts
        bit 1: hard disk write counts
        bit 2: RAM disk read/write counts
Note:    multiple commands may be placed in a single packet by stringing
      together as many command/argument pairs as desired

Bitfields for options byte:
 bit 0    cache off
 bit 1    cache frozen
 bit 2    write caching enabled
 bit 3    delayed writing disabled
 bit 5    fix memory allocation (no XMS lending)
 bit 6    no 'sector not found' error

Format of block info:
Offset    Size    Description
 00h    DWORD    block ID
 04h    BYTE    bitmask of valid sectors in block
 05h    BYTE    bitmask of dirty sectors in block
 06h    BYTE    last error returned by BIOS
 07h    BYTE    number of errors
--------D-214406-----------------------------
INT 21 - DOS 2+ - IOCTL - GET INPUT STATUS
    AX = 4406h
    BX = file handle
Return: CF clear if successful
        AL = input status
        00h not ready (device) or at EOF (file)
        FFh ready
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    files may not register as being at EOF if positioned there by AH=42h
SeeAlso: AX=4407h,INT 2F/AX=122Bh
--------D-214407-----------------------------
INT 21 - DOS 2+ - IOCTL - GET OUTPUT STATUS
    AX = 4407h
    BX = file handle
Return: CF clear if successful
        AL = input status
        00h not ready
        FFh ready
    CF set on error
        AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:    for DOS 2+, files are always ready for output, even if the disk is
      full or no media is in the drive
SeeAlso: AX=4406h,INT 2F/AX=122Bh
--------D-214408-----------------------------
INT 21 - DOS 3.0+ - IOCTL - CHECK IF BLOCK DEVICE REMOVABLE
    AX = 4408h
    BL = drive number (00h = default, 01h = A:, etc)
Return: CF clear if successful
        AX = 0000h if removable
           = 0001h if fixed
    CF set on error
        AX = error code (01h,0Fh) (see AH=59h)
SeeAlso: AX=4400h,AX=4409h,INT 2F/AX=122Bh
--------D-214409-----------------------------
INT 21 - DOS 3.1+ - IOCTL - CHECK IF BLOCK DEVICE REMOTE
    AX = 4409h
    BL = drive number (00h = default, 01h = A:, etc)
Return: CF clear if successful
        DX = device attribute word
        bit 15: drive is SUBSTituted
        bit 12: drive is remote
        bit  9: direct I/O not allowed
    CF set on error
        AX = error code (01h,0Fh) (see AH=59h)
Note:    on local drives, DX bits not listed above are the attribute word from
      the device driver header (see AH=52h); for remote drives, the other
      bits appear to be undefined for DOS versions prior to 5.0 (they are
      all cleared in DOS 5+)
SeeAlso: AX=4400h,AX=4408h,AX=440Ah,INT 2F/AX=122Bh
--------D-21440A-----------------------------
INT 21 - DOS 3.1+ - IOCTL - CHECK IF HANDLE IS REMOTE
    AX = 440Ah
    BX = handle
Return: CF clear if successful
        DX = attribute word (as stored in SFT)
        bit 15: set if remote
        bit 14: date/time not set on close
    CF set on error
        AX = error code (01h,06h) (see AH=59h)
Notes:    if file is remote, Novell Advanced NetWare 2.0 returns the number of
      the file server on which the handle is located in CX
    DR-DOS 3.41 and 5.0 clear all bits of DX except bit 15
SeeAlso: AX=4400h,AX=4409h,AH=52h,INT 2F/AX=122Bh
--------D-21440B-----------------------------
INT 21 - DOS 3.1+ - IOCTL - SET SHARING RETRY COUNT
    AX = 440Bh
    CX = pause between retries (default 1)
    DX = number of retries (default 3)
Return: CF clear if successful
    CF set on error
        AX = error code (01h) (see AH=59h)
Notes:    delay is dependent on processor speed (value in CX specifies number of
      64K-iteration empty loops to execute)
    if DX=0000h on entry, the retry count is left unchanged
SeeAlso: AH=52h,INT 2F/AX=1224h,INT 2F/AX=122Bh
--------D-21440C-----------------------------
INT 21 - DOS 3.2+ - IOCTL - GENERIC CHARACTER DEVICE REQUEST
    AX = 440Ch
    BX = device handle
    CH = category code
        00h unknown (DOS 3.3+)
        01h COMn: (DOS 3.3+)
        03h CON (DOS 3.3+)
        05h LPTn:
        9Eh Media Access Control driver (STARLITE)
        00h-7Fh reserved for Microsoft
        80h-FFh reserved for OEM/user-defined
    CL = function
        00h MAC driver Bind (STARLITE)
        45h set iteration (retry) count
        4Ah select code page
        4Ch start code-page preparation
        4Dh end code-page preparation
        5Fh set display information (DOS 4+)
        65h get iteration (retry) count
        6Ah query selected code page
        6Bh query prepare list
        7Fh get display information (DOS 4+)
    DS:DX -> parameter block (see below)
    SI = parameter to pass to driver (European MS-DOS 4.0, OS/2 comp box)
    DI = parameter to pass to driver (European MS-DOS 4.0, OS/2 comp box)
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        DS:DX -> iteration count if CL=65h
        SI = returned value (European MS-DOS 4.0, OS/2 comp box)
        DI = returned value (European MS-DOS 4.0, OS/2 comp box)
Notes:    bit assignments for function code in CL:
        bit 7: set to ignore if unsupported, clear to return error
        bit 6: set if passed to driver, clear if intercepted by DOS
        bit 5: set if queries data from device, clear if sends command
        bits 4-0: subfunction
    DR-DOS 3.41 and 5.0 return error code 16h on CL=45h,65h if the device
      does not support a retry counter
SeeAlso: AX=440Dh,INT 2F/AX=0802h,INT 2F/AX=122Bh,INT 2F/AX=14FFh
SeeAlso: INT 2F/AX=1A01h

Format of parameter block for function 00h:
Offset    Size    Description
 00h  8 BYTEs    ASCIZ signature "STARMAC"
 08h    WORD    version
 0Ah    WORD    flags
        bit 0: media requires connect or listen request before use
        bit 1: network is a LAN (broadcast/multicast supported)
        bit 2: point-to-point network
 0Ch    WORD    handle for use with MAC driver's private interface (filled in
        by MAC driver)
 0Eh    WORD    context
 10h    WORD    approximate speed in KB/sec (filled in by MAC driver)
 12h    WORD    approximate cost in cents per hour (filled in by MAC driver)
 14h    WORD    maximum packet size in bytes (filled in by MAC driver)
 16h    WORD    addressing format (filled in by MAC driver)
        0000h general addressing
        0001h Ethernet addressing
        0002h Token Ring addressing
        0003h Token Bus addressing
 18h    DWORD    Send entry point (filled in by MAC driver)
 1Ch    DWORD    RegisterEventHandler entry point (filled in by MAC driver)
 20h    DWORD    SetPacketFilter entry point (filled in by MAC driver)
 24h    DWORD    UnBind entry point (filled in by MAC driver)

Format of parameter block for function 45h:
Offset    Size    Description
 00h    WORD    number of times output is attempted before driver assumes
        device is busy

Format of parameter block for functions 4Ah and 6Ah:
Offset    Size    Description
 00h    WORD    length of data
 02h    WORD    code page ID
 04h 2N BYTEs    DCBS (double byte character set) lead byte range
          start/end for each of N ranges (DOS 4.0)
    WORD    0000h  end of data (DOS 4.0)

Format of parameter block for function 4Ch:
Offset    Size    Description
 00h    WORD    flags
        DISPLAY.SYS = 0000h
        PRINTER.SYS bit 0 clear to prepare downloaded font, set to
            prepare cartridge selection
 02h    WORD    length of remainder of parameter block
 04h    WORD    number of code pages following
 06h  N WORDs    code page 1,...,N

Format of parameter block for function 4Dh:
Offset    Size    Description
 00h    WORD    length of data
 02h    WORD    code page ID

Format of parameter block for functions 5Fh and 7Fh:
Offset    Size    Description
 00h    BYTE    level (0 for DOS 4.x-6.0)
 01h    BYTE    reserved (0)
 02h    WORD    length of following data (14)
 04h    WORD    control flags
          bit 0 set for blink, clear for intensity
          bits 1 to 15 reserved
 06h    BYTE    mode type (1=text, 2=graphics)
 07h    BYTE    reserved (0)
 08h    WORD    colors
           0 = monochrome
           else N bits per pixel
 0Ah    WORD    pixel columns
 0Ch    WORD    pixel rows
 0Eh    WORD    character columns
 10h    WORD    character rows

Format of parameter block for function 6Bh:
Offset    Size    Description
 00h    WORD    length of following data
 02h    WORD    number of hardware code pages
 04h  N WORDs    hardware code pages 1,...,N
    WORD    number of prepared code pages
      N WORDs    prepared code pages 1,...,N
--------d-21440C-----------------------------
INT 21 - Greg Shenaut ASPITAPE.SYS - INTERFACE
    AX = 440Ch
    BX = device handle
    CH = category code
        07h tape (ASPITAPE.SYS)
    CL = function
        01h "mtop" - perform tape operation
        02h "mtget" - get tape status
        03h ignore end-of-tape errors
        04h enable end-of-tape errors
    DS:DX -> parameter block (see below)
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        DS:DX -> data block
Notes:    This device driver is a simple DOS interface to the Adaptec Advanced
      SCSI Programming Interface (ASPI).  It provides the following device
      names as access to the SCSI tape, 'RMTx' (rewind on close) and
      'NRMTx' (NO rewind on close) where x can go from 0 to 3.  There may
      also be the following names 'MTx' and 'NMTx' which default to 1024
      byte blocks.    The names may also have a '$' appended to try and make
      them unique from file names of 'RMT0' etc.
    once opend these devices must be put into RAW mode
SeeAlso: AX=4402h"ASPI"

Format of mtop parameter block:
Offset    Size    Description
 00h    WORD    operation code
        00h "MTWEOF" - write an end-of-file record
        01h "MTFSF" - forward space file
        02h "MTBSF" - backward space file
        03h "MTFSR" - forward space record
        04h "MTBSR" - backward space record
        05h "MTREW" - rewind
        06h "MTOFFL" - rewind and unload
        07h "MTNOP" - perform TEST UNIT READY
 02h    DWORD    repetition count

Format of mtget parameter block:
Offset    Size    Description
 00h    BYTE    ASPI host ID
 01h    BYTE    SCSI target ID
 02h    BYTE    SCSI logical unit number
 03h    BYTE    device parameters
        bit 0: drive must use fixed-block read and write
        bit 7: drive is an ASPI device
 04h    BYTE    current device state (see below)
 05h    BYTE    unit number within driver
 06h    WORD    fixed block blocksize
 08h    BYTE    last SCSI status
 09h    BYTE    last SCSI sense key
 0Ah    WORD    last SCSI opcode (packed)
        bits 0-7: SCSI operation (SCSI packet byte 0)
        bits 8-10: SCSI flags (SCSI packet byte 1)
        bits 11-12: ASPI "Direction Bits" (ASPI SRB byte 3)
 0Ch    WORD    residual bytes from SCSI opcode

Bitfields for current device state:
 bit 0    device currently opened in buffered mode
 bit 1    drive currently opened in nonbuffered mode
 bit 2    rewind drive on last close
 bit 3    drive has been written on
 bit 4    drive has been read from
 bit 5    next read will return 0 bytes
 bit 6    EOM will resemble EOF
 bit 7    drive may be busy rewinding
--------D-21440D-----------------------------
INT 21 - DOS 3.2+ - IOCTL - GENERIC BLOCK DEVICE REQUEST
    AX = 440Dh
    BL = drive number (00h=default,01h=A:,etc)
    CH = category code
        08h disk drive
        00h-7Fh reserved for Microsoft
        80h-FFh reserved for OEM/user-defined
    CL = minor code (function) (see below)
    DS:DX -> (DOS) parameter block (see below)
    SI:DI -> (OS/2 comp box) parameter block (see below)
Return: CF set on error
        AX = error code (01h,02h) (see AH=59h)
    CF clear if successful
        DS:DX -> data block if CL=60h or CL=61h
Notes:    DOS 4.01 seems to ignore the high byte of the number of directory
      entries in the BPB for diskettes.
    functions 46h and 66h undocumented in DOS 4.x, documented for DOS 5+
    the DUBLDISK.SYS v2.6 driver only supports minor codes 60h and 67h
    DR-DOS 3.41-6.0 only support minor codes 40h-42h and 60h-62h; all
      other minor codes return error code 16h
SeeAlso: AX=440Ch,AH=69h,INT 2F/AX=0802h,INT 2F/AX=122Bh

Values for minor code:
 00h    (OS/2)    \ used to lock/unlock a drive
 01h    (OS/2)    /
 40h    set device parameters
 41h    write logical device track
 42h    format and verify logical device track
 46h    (DOS 4+) set volume serial number (see also AH=69h)
 47h    (DOS 4+) set access flag
 50h    (PCMCIA) attribute memory write
 51h    (PCMCIA) common memory write
 52h    (PCMCIA) force media change
 53h    (PCMCIA) erase drive
 54h    (PCMCIA) erase media
 56h    (PCMCIA) set erase status callback
 57h    (PCMCIA) append Card Information Structure (CIS) tuple
 58h    (PCMCIA) erase CIS tuples
 60h    get device parameters
 61h    read logical device track
 62h    verify logical device track
 66h    (DOS 4+) get volume serial number (see also AH=69h)
 67h    (DOS 4+) get access flag
 68h    (DOS 5+) sense media type
 70h    (PCMCIA) attribute memory read
 73h    (PCMCIA) get memory media information
 76h    (PCMCIA) get erase status callback
 77h    (PCMCIA) get first Card Information Structure (CIS) tuple
 78h    (PCMCIA) get next CIS tuple

Format of parameter block for functions 40h, 60h:
Offset    Size    Description
 00h    BYTE    special functions
        bit 0 set if function to use current BPB, clear if Device
            BIOS Parameter Block field contains new default BPB
        bit 1 set if function to use track layout fields only
            must be clear if CL=60h
        bit 2 set if all sectors in track same size (should be set)
        bits 3-7 reserved
 01h    BYTE    device type (see below)
 02h    WORD    device attributes
        bit 0 set if nonremovable medium
        bit 1 set if door lock ("changeline") supported
        bits 2-15 reserved
 04h    WORD    number of cylinders
 06h    BYTE    media type
        for 1.2M drive
            00h 1.2M disk (default)
            01h 320K/360K disk
        F8h for DUBLDISK.SYS v2.6 expanded drives
        always 00h for other drive types
 07h 31 BYTEs    device BPB (see AH=53h), bytes after BPB offset 1Eh omitted
---function 40h only---
 26h    WORD    number of sectors per track (start of track layout field)
        max 63
 28h  N word pairs: number,size of each sector in track

Values for device type:
 00h    320K/360K disk
 01h    1.2M disk
 02h    720K disk
 03h    single-density 8-inch disk
 04h    double-density 8-inch disk
 05h    fixed disk
 06h    tape drive
 07h    (DOS 3.3+) other type of block device, normally 1.44M floppy
 08h    read/write optical disk
 09h    (DOS 5+) 2.88M floppy

Format of parameter block for functions 41h, 61h:
Offset    Size    Description
 00h    BYTE    special functions (reserved, must be zero)
 01h    WORD    number of disk head
 03h    WORD    number of disk cylinder
 05h    WORD    number of first sector to read/write
 07h    WORD    number of sectors
 09h    DWORD    transfer address

Format of parameter block for function 42h:
Offset    Size    Description
 00h    BYTE    reserved, must be zero (DOS <3.2)
          bit 0=0: format/verify track
            1: format status call (DOS 3.2+), don't actually format
          bits 1-7 reserved, must be zero
        on return (DOS 4.x):
          bit 0: set if specified tracks, sectors/track supported
          bit 1: set if function not supported by BIOS
          bit 2: set if specified tracks, sectors/track not supported
          bit 3: set if no disk in drive
 01h    WORD    number of disk head
 03h    WORD    number of disk cylinder

Format of parameter block for function 62h:
Offset    Size    Description
 00h    BYTE    reserved, must be zero (DOS <3.2)
          bit 0=0: verify single track
            1: verify multiple tracks
          bits 1-7 reserved, must be zero
        on return (DOS 4.x):
          bit 0: set if specified tracks, sectors/track supported
          bit 1: set if function not supported by BIOS
          bit 2: set if specified tracks, sectors/track not supported
          bit 3: set if no disk in drive
 01h    WORD    number of disk head
 03h    WORD    number of disk cylinder
 05h    WORD    number of tracks to verify (equivalent to 255 or fewer sectors)

Format of parameter block for functions 46h, 66h:
Offset    Size    Description
 00h    WORD    (call) info level (should be 0000h)
 02h    DWORD    disk serial number (binary)
 06h 11 BYTEs    volume label or "NO NAME    "
 11h  8 BYTEs    filesystem type "FAT12     " or "FAT16   " (CL=66h only)

Format of parameter block for functions 47h, 67h:
Offset    Size    Description
 00h    BYTE    special-function field (must be zero)
 01h    BYTE    disk-access flag, nonzero if access allowed by driver

Format of parameter block for function 68h:
Offset    Size    Description
 00h    BYTE    01h for default media type, 00h for any other media type
        (see also INT 13/AH=20h)
 01h    BYTE    02h for 720K, 07h for 1.44M, 09h for 2.88M
--------D-21440E-----------------------------
INT 21 - DOS 3.2+ - IOCTL - GET LOGICAL DRIVE MAP
    AX = 440Eh
    BL = drive number (00h=default,01h=A:,etc)
Return: CF set on error
        AX = error code (01h,0Fh) (see AH=59h)
    CF clear if successful
        AL = 00h block device has only one logical drive assigned
         1..26 the last letter used to reference the drive (1=A:,etc)
Note:    DR-DOS 3.41-5.0 DRIVER.SYS does not support drive mapping and thus
      always returns AL=00h
SeeAlso: AX=440Fh,INT 2F/AX=122Bh
--------D-21440F-----------------------------
INT 21 - DOS 3.2+ - IOCTL - SET LOGICAL DRIVE MAP
    AX = 440Fh
    BL = physical drive number (00h=default,01h=A:,etc))
Return: CF set on error
        AX = error code (01h,0Fh) (see AH=59h)
    CF clear if successful
        drive now responds to next logical drive number
Notes:    maps logical drives to physical drives, similar to DOS's treatment of
      a single physical floppy drive as both A: and B:
    DR-DOS 3.41-5.0 DRIVER.SYS does not support drive mapping and thus
      always returns an error on this function
SeeAlso: AX=440Eh,INT 2F/AX=122Bh
--------D-214410-----------------------------
INT 21 - DOS 5+ - IOCTL - QUERY GENERIC IOCTL CAPABILITY (HANDLE)
    AX = 4410h
    BX = handle for device
    CH = category code (see AX=440Ch)
    CL = function code
Return: CF clear if successful
        AX = 0000h    specified IOCTL function is supported
    CF set on error
        AL = 01h    IOCTL capability not available
Note:    a program which wishes to use Generic IOCTL calls beyond those in the
      standard DOS 3.2 set may use this call first to see whether a
      particular call is supported
SeeAlso: AX=440Ch,AX=440Dh,AX=4411h
--------d-214410BXFFFF-----------------------
INT 21 U - NewSpace - ENABLE DRIVER
    AX = 4410h
    BX = FFFFh
Program: NewSpace is a TSR by Isogon Corporation which automatically compresses
      all files as they are written and decompresses them as they are read
Note:    compressed files are not accessible unless the driver is enabled
SeeAlso: AX=4411h/BX=FFFFh
--------D-214411-----------------------------
INT 21 - DOS 5+ - IOCTL - QUERY GENERIC IOCTL CAPABILITY (DRIVE)
    AX = 4411h
    BL = drive number
    CH = category code (see AX=440Dh)
    CL = function code
Return: CF clear if successful
        AX = 0000h    specified IOCTL function is supported
    CF set on error
        AL = 01h    IOCTL capability not available
Note:    a program which wishes to use Generic IOCTL calls beyond those in the
      standard DOS 3.2 set may use this call first to see whether a
      particular call is supported
SeeAlso: AX=440Ch,AX=440Dh,AX=4410h
--------d-214411BXFFFF-----------------------
INT 21 U - NewSpace - DISABLE DRIVER
    AX = 4411h
    BX = FFFFh
Program: NewSpace is a TSR by Isogon Corporation which automatically compresses
      all files as they are written and decompresses them as they are read
Note:    compressed files are not accessible unless the driver is enabled
SeeAlso: AX=4410h/BX=FFFFh
--------O-214412-----------------------------
INT 21 - DR-DOS 5+ - DETERMINE DOS TYPE
    AX = 4412h
    CF set
Return: CF set if not DR-DOS
        AX = error code (see AH=59h)
    CF clear if DR-DOS
        DX = AX = version code (see AX=4452h)
Note:    this obsolete call which will not be supported in future versions of
      DR-DOS is identical to AX=4452h
SeeAlso: AX=4452h
--------d-214412BXFFFF-----------------------
INT 21 U - NewSpace - INSTALLATION CHECK???
    AX = 4412h
    BX = FFFFh
Return: AX = PSP segment of NewRes (resident driver for NewSpace)
    BX:DX -> ???
    CX = ???
SeeAlso: AX=4411h/BX=FFFFh
--------d-214413BXFFFF-----------------------
INT 21 U - NewSpace - GET ???
    AX = 4413h
    BX = FFFFh
Return: AX = code segment of NewRes (resident driver for NewSpace)
    BX = offset of ???
SeeAlso: AX=4412h/BX=FFFFh
--------O-214414-----------------------------
INT 21 U - DR-DOS 5.0 - SET GLOBAL PASSWORD
    AX = 4414h
    DS:DX -> password string (blank-padded to 8 characters)
Desc:    Specify the master password for accessing files.
Note:    this obsolete call which will not be supported in future versions of
      DR-DOS is identical to AX=4452h
SeeAlso: AX=4454h
--------d-214414BXFFFF-----------------------
INT 21 U - NewSpace - DEBUGGING DUMP
    AX = 4414h
    BX = FFFFh
Return: debugging dump written to X:\NEWSPACE.SMP
SeeAlso: AX=4413h/BX=FFFFh,AX=44FFh/BX=FFFFh
--------O-2144-------------------------------
INT 21 U - DR-DOS 5.0 - HISTORY BUFFER, SHARE, AND HILOAD CONTROL
    AH = 44h
    AL = 16h to 18h
Note:    these obsolete subfunctions (which will not be supported in future
      versions of DR-DOS) are identical to AX=4456h through 4458h
SeeAlso: AX=4456h,AX=4457h,AX=4458h
--------O-214451-----------------------------
INT 21 - Concurrent DOS v3.2+ - INSTALLATION CHECK
    AX = 4451h
Return: CF set if not Concurrent DOS
        AX = error code (see AH=59h)
    CF clear if successful
        AH = single-user/multiuser nature
        10h single-user
            AL = operating system version ID (see AX=4452h)
        14h multiuser
            AL = operating system version ID (see below)
Notes:    as of Concurrent DOS/XM 5.0 (possibly earlier), the version is stored
      in the environment variable VER
    use this function if you are looking for multiuser capabilities,
      AX=4452h for single-user
    this function should never return the single-user values
SeeAlso: AX=4452h,AX=4459h

Values for operating system version ID:
 32h    Concurrent PC DOS 3.2
 41h    Concurrent DOS 4.1
 50h    Concurrent DOS/XM 5.0 or Concurrent DOS/386 1.1
 60h    Concurrent DOS/XM 6.0 or Concurrent DOS/386 2.0
 62h    Concurrent DOS/XM 6.2 or Concurrent DOS/386 3.0
 66h    DR Multiuser DOS 5.1
 67h    Concurrent DOS 5.1
--------O-214452-----------------------------
INT 21 - DR-DOS 3.41+ - DETERMINE DOS TYPE/GET DR-DOS VERSION
    AX = 4452h ("DR")
    CF set
Return: CF set if not DR-DOS
        AX = error code (see AH=59h)
    CF clear if DR-DOS
        DX = AX = version code
        AH = single-user/multiuser nature
        10h single-user
            AL = operating system version ID (see below)
        14h multiuser
            AL = operating system version ID (see AX=4451h)
Notes:    the DR-DOS version is stored in the environment variable VER
    use this function if looking for single-user capabilities, AX=4451h
      if looking for multiuser; this call should never return multiuser
      values
SeeAlso: AX=4412h,AX=4451h,AX=4459h

Values for operating system version ID:
 60h    DOS Plus
 63h    DR-DOS 3.41
 64h    DR-DOS 3.42
 65h    DR-DOS 5.00
 67h    DR-DOS 6.00
 70h    PalmDOS
 71h    DR-DOS 6.0 March 1993 "business update"
 72h    Novell DOS 7.0
--------O-214454-----------------------------
INT 21 U - DR-DOS 3.41+ - SET GLOBAL PASSWORD
    AX = 4454h
    DS:DX -> password string (blank-padded to 8 characters)
Desc:    Specify the master password for accessing files.
SeeAlso: AX=4303h,AX=4414h
--------O-214456-----------------------------
INT 21 U - DR-DOS 5.0+ - HISTORY BUFFER CONTROL
    AX = 4456h
    DL = flag
        bit 0: 1 = COMMAND.COM history buffers
           0 = set to application
Return: AL = ??? (20h if DL bit 0 set, A0h if clear (DR-DOS 6.0))
Note:    This was seen called by COMMAND.COM of DR-DOS 6.0
--------O-214457-----------------------------
INT 21 U - DR-DOS 5.0+ - SHARE/HILOAD CONTROL
    AX = 4457h
    DH = subfunction
        00h enable/disable SHARE
        DL = 00h disable
           = 01h enable
           else Return: AX = ???
        01h get HILOAD status
        Return: AX = status
                0000h off
                0001h on
        02h set HILOAD status
        DL = new state (00h off, 01h on)
        Return: AX = ???
        other
        Return: AX = ???
Note:    This was seen called by COMMAND.COM of DR-DOS 6.0
SeeAlso: AX=4457h/DX=FFFFh
--------O-214457DXFFFF-----------------------
INT 21 U - DR-DOS 6.0 - GET SHARE STATUS
    AX = 4457h
    DX = FFFFh
Return: AX = SHARE status
SeeAlso: INT 2F/AX=1000h
--------O-214458-----------------------------
INT 21 U - DR-DOS 5.0+ internal - GET POINTER TO INTERNAL VARIABLE TABLE
    AX = 4458h
Return: ES:BX -> internal variable table (see below)
    AX = ??? (0B50h for DR-DOS 5.0, 0A56h for DR-DOS 6.0)
SeeAlso: AX=4452h

Format of internal variable table:
Offset    Size    Description
 00h    WORD    ???
 02h    WORD    segment of ???
 04h  7 BYTEs    ???
 0Bh    WORD    KB of extended memory at startup
 0Dh    BYTE    number of far jump entry points
 0Eh    WORD    segment containing far jumps to DR-DOS entry points (see below)
 10h    WORD    (only if kernel loaded in HMA) offset in HMA of first free HMA
        memory block (see below) or 0000h if none; segment is FFFFh
 12h    WORD    pointer to segment of environment variables set in CONFIG,
        or 0000h if already used
---DR-DOS 6.0---
 14h    WORD    (only if kernel loaded in HMA) offset in HMA of first used HMA
        memory block (see below) or 0000h if none; segment is FFFFh
Note:    the segment used for the DR-DOS 6.0 CONFIG environment variables
      (excluding COMSPEC, VER and OS) is only useful for programs/drivers
      called from CONFIG.SYS. The word is set to zero later when the area
      is copied to the COMMAND.COM environment space.  This allows
      CONFIG.SYS to pass information to AUTOEXEC.BAT.

Format of kernel entry jump table for DR-DOS 5.0-6.0:
Offset    Size    Description
 00h  5 BYTEs    far jump to kernel entry point for CP/M CALL 5
 05h  5 BYTEs    far jump to kernel entry point for INT 20
 0Ah  5 BYTEs    far jump to kernel entry point for INT 21
 0Fh  5 BYTEs    far jump to kernel entry point for INT 22 (RETF)
 14h  5 BYTEs    far jump to kernel entry point for INT 23 (RETF)
 19h  5 BYTEs    far jump to kernel entry point for INT 24
 1Eh  5 BYTEs    far jump to kernel entry point for INT 25
 23h  5 BYTEs    far jump to kernel entry point for INT 26
 28h  5 BYTEs    far jump to kernel entry point for INT 27
 2Dh  5 BYTEs    far jump to kernel entry point for INT 28
 32h  5 BYTEs    far jump to kernel entry point for INT 2A (IRET)
 37h  5 BYTEs    far jump to kernel entry point for INT 2B (IRET)
 3Ch  5 BYTEs    far jump to kernel entry point for INT 2C (IRET)
 41h  5 BYTEs    far jump to kernel entry point for INT 2D (IRET)
 46h  5 BYTEs    far jump to kernel entry point for INT 2E (IRET)
 4Bh  5 BYTEs    far jump to kernel entry point for INT 2F
Notes:    all of these entry points are indirected through this jump table
      to allow the kernel to be relocated into high memory while leaving
      the actual entry addresses in low memory for maximum compatibility
    some of these entry points (22h,23h,24h,2Eh,2Fh) are replaced as soon
      as COMMAND.COM is loaded, and return immediately to the caller, some
      returning an error code (the original handler for INT 2F returns
      AL=03h [fail]).

Format of HMA Memory Block (DR-DOS 6.0 kernel loaded in HMA):
Offset    Size    Description
 00h    WORD    offset of next HMA Memory Block (0000h if last block)
 02h    WORD    size of this block in bytes (at least 10h)
 04h    BYTE    type of HMA Memory Block (interpreted by MEM)
        00h system
        01h KEYB
        02h NLSFUNC
        03h SHARE
        04h TaskMAX
        05h COMMAND
 05h    var    TSR (or system) code and data. DR-DOS TSR's, such as KEYB,
        hooks interrupts using segment FFFEh instead FFFFh.
--------O-214459-----------------------------
INT 21 - DR MultiUser DOS 5.0 - API
    AX = 4459h
    CL = function (see INT E0"CP/M")
    DS,DX = parameters
Notes:    DR-DOS 5.0 returns CF set and AX=0001h
    this API is also available on INT E0
SeeAlso: AX=4452h,INT E0"CP/M"
--------N-2144E0-----------------------------
INT 21 U - Sun PC-NFS - API???
    AX = 44E0h
    DS:DX -> ???
    SS:BP -> stack frame (see below)
Return: ???
Note:    this function is also supported by Beame&Whiteside's BWPCNFS shim; the
      description presented here was derived from that shim

Format of stack frame:
Offset    Size    Description
 00h    WORD    -> previous stack frame
 02h    DWORD    return address
--------d-2144FFBXFFFF-----------------------
INT 21 U - NewSpace - ???
    AX = 44FFh
    BX = FFFFh
    DX = ???
Program: NewSpace is a TSR by Isogon Corporation which automatically compresses
      all files as they are written and decompresses them as they are read
SeeAlso: AX=4414h/BX=FFFFh
--------D-2145-------------------------------
INT 21 - DOS 2+ - "DUP" - DUPLICATE FILE HANDLE
    AH = 45h
    BX = file handle
Return: CF clear if successful
        AX = new handle
    CF set on error
        AX = error code (04h,06h) (see AH=59h)
Notes:    moving file pointer for either handle will also move it for the other,
      because both will refer to the same system file table
    for DOS versions prior to 3.3, file writes may be forced to disk by
      duplicating the file handle and closing the duplicate
SeeAlso: AH=3Dh,AH=46h
--------D-2146-------------------------------
INT 21 - DOS 2+ - "DUP2", "FORCEDUP" - FORCE DUPLICATE FILE HANDLE
    AH = 46h
    BX = file handle
    CX = file handle to become duplicate of first handle
Return: CF clear if successful
    CF set on error
        AX = error code (04h,06h) (see AH=59h)
Notes:    closes file with handle CX if it is still open
    DOS 3.30 hangs if BX=CX on entry
    moving file pointer for either handle will also move it for the other,
      because both will refer to the same system file table
SeeAlso: AH=3Dh,AH=45h
--------D-2147-------------------------------
INT 21 - DOS 2+ - "CWD" - GET CURRENT DIRECTORY
    AH = 47h
    DL = drive number (00h = default, 01h = A:, etc)
    DS:SI -> 64-byte buffer for ASCIZ pathname
Return: CF clear if successful
        AX = 0100h (undocumented)
    CF set on error
        AX = error code (0Fh) (see AH=59h)
Notes:    the returned path does not include a drive or the initial backslash
    many Microsoft products for Windows rely on AX being 0100h on success
    under the FlashTek X-32 DOS extender, the buffer pointer is in DS:ESI
SeeAlso: AH=19h,AH=3Bh,INT 15/AX=DE25h
--------D-2148-------------------------------
INT 21 - DOS 2+ - ALLOCATE MEMORY
    AH = 48h
    BX = number of paragraphs to allocate
Return: CF clear if successful
        AX = segment of allocated block
    CF set on error
        AX = error code (07h,08h) (see AH=59h)
        BX = size of largest available block
Notes:    DOS 2.1-6.0 coalesces free blocks while scanning for a block to
      allocate
    .COM programs are initially allocated the largest available memory
      block, and should free some memory with AH=49h before attempting any
      allocations
    under the FlashTek X-32 DOS extender, EBX contains a protected-mode
      near pointer to the allocated block on a successful return
SeeAlso: AH=49h,AH=4Ah,AH=58h,AH=83h
--------D-2149-------------------------------
INT 21 - DOS 2+ - FREE MEMORY
    AH = 49h
    ES = segment of block to free
Return: CF clear if successful
    CF set on error
        AX = error code (07h,09h) (see AH=59h)
Notes:    apparently never returns an error 07h, despite official docs; DOS 3.30
      code contains only an error 09h exit
    DOS 2.1-6.0 does not coalesce adjacent free blocks when a block is
      freed, only when a block is allocated or resized
    the code for this function is identical in DOS 2.1-6.0 except for
      calls to start/end a critical section in DOS 3+
SeeAlso: AH=48h,AH=4Ah
--------D-214A-------------------------------
INT 21 - DOS 2+ - RESIZE MEMORY BLOCK
    AH = 4Ah
    BX = new size in paragraphs
    ES = segment of block to resize
Return: CF clear if successful
    CF set on error
        AX = error code (07h,08h,09h) (see AH=59h)
        BX = maximum paragraphs available for specified memory block
Notes:    under DOS 2.1-6.0, if there is insufficient memory to expand the block
      as much as requested, the block will be made as large as possible
    DOS 2.1-6.0 coalesces any free blocks immediately following the block
      to be resized
SeeAlso: AH=48h,AH=49h,AH=83h
--------D-214B-------------------------------
INT 21 - DOS 2+ - "EXEC" - LOAD AND/OR EXECUTE PROGRAM
    AH = 4Bh
    AL = type of load
        00h load and execute
        01h load but do not execute
        03h load overlay
        04h load and execute in background (European MS-DOS 4.0 only)
        "Exec & Go" (see also AH=80h)
    DS:DX -> ASCIZ program name (must include extension)
    ES:BX -> parameter block (see below)
    CX = mode (subfunction 04h only)
        0000h child placed in zombie mode after termination
        0001h child's return code discarded on termination
Return: CF clear if successful
        BX,DX destroyed
        if subfunction 01h, process ID set to new program's PSP; get with
        INT 21/AH=62h
    CF set on error
        AX = error code (01h,02h,05h,08h,0Ah,0Bh) (see AH=59h)
Notes:    DOS 2.x destroys all registers, including SS:SP
    under ROM-based DOS, if no disk path characters (colons or slashes)
      are included in the program name, the name is searched for in the
      ROM module headers (see below) before searching on disk
    for functions 00h and 01h, the calling process must ensure that there
      is enough unallocated memory available; if necessary, by releasing
      memory with AH=49h or AH=4Ah
    for function 01h, the AX value to be passed to the child program is put
      on top of the child's stack
    for function 03h, DOS assumes that the overlay is being loaded into
      memory allocated by the caller
    function 01h was undocumented prior to the release of DOS 5.0
    some versions (such as DR-DOS 6.0) check the parameters and parameter
      block and return an error if an invalid value (such as an offset of
      FFFFh) is found
    background programs under European MS-DOS 4.0 must use the new
      executable format
    new executables begin running with the following register values
        AX = environment segment
        BX = offset of command tail in environment segment
        CX = size of automatic data segment (0000h = 64K)
        ES,BP = 0000h
        DS = automatic data segment
        SS:SP = initial stack
      the command tail corresponds to an old executable's PSP:0081h and
      following, except that the 0Dh is turned into a NUL (00h); new
      format executables have no PSP
    under the FlashTek X-32 DOS extender, only function 00h is supported
      and the pointers are passed in DS:EDX and ES:EBX
    DR-DOS 6 always loads .EXE-format programs with no fixups above the
      64K mark to avoid the EXEPACK bug
    names for the various executable type understood by various
      environments:
        MZ  old-style DOS executable
        NE  Windows or OS/2 1.x segmented ("new") executable
        LE  Windows virtual device driver (VxD) linear executable
        LX  variant of LE used in OS/2 2.x
        W3  Windows WIN386.EXE file; a collection of LE files
        PE  Win32 (Windows NT and Win32s) portable executable based on
            Unix COFF
BUGS:    DOS 2.00 assumes that DS points at the current program's PSP
    Load Overlay (subfunction 03h) loads up to 512 bytes too many if the
      file contains additional data after the actual overlay
SeeAlso: AX=4B05h,AH=4Ch,AH=4Dh,AH=64h"OS/2",AH=8Ah,INT 2E

Format of EXEC parameter block for AL=00h,01h,04h:
Offset    Size    Description
 00h    WORD    segment of environment to copy for child process (copy caller's
        environment if 0000h)
 02h    DWORD    pointer to command tail to be copied into child's PSP
 06h    DWORD    pointer to first FCB to be copied into child's PSP
 0Ah    DWORD    pointer to second FCB to be copied into child's PSP
 0Eh    DWORD    (AL=01h) will hold subprogram's initial SS:SP on return
 12h    DWORD    (AL=01h) will hold entry point (CS:IP) on return

Format of EXEC parameter block for AL=03h:
Offset    Size    Description
 00h    WORD    segment at which to load overlay
 02h    WORD    relocation factor to apply to overlay if in .EXE format

Format of EXEC parameter block for FlashTek X-32:
Offset    Size    Description
 00h    PWORD    48-bit far pointer to environment string
 06h    PWORD    48-bit far pointer to command tail string

Format of .EXE file header:
Offset    Size    Description
 00h  2 BYTEs    .EXE signature, either "MZ" or "ZM" (5A4Dh or 4D5Ah)
 02h    WORD    number of bytes in last 512-byte page of executable
 04h    WORD    total number of 512-byte pages in executable (includes any
        partial last page)
 06h    WORD    number of relocation entries
 08h    WORD    header size in paragraphs
 0Ah    WORD    minimum paragraphs of memory to allocation in addition to
        executable's size
 0Ch    WORD    maximum paragraphs to allocate in addition to executable's size
 0Eh    WORD    initial SS relative to start of executable
 10h    WORD    initial SP
 12h    WORD    checksum (one's complement of sum of all words in executable)
 14h    DWORD    initial CS:IP relative to start of executable
 18h    WORD    offset within header of relocation table
        40h or greater for new-format (NE,LE,LX,W3,PE,etc.) executable
 1Ah    WORD    overlay number (normally 0000h = main program)
---new executable---
 1Ch  4 BYTEs    ???
 20h    WORD    behavior bits
 22h 26 BYTEs    reserved for additional behavior info
 3Ch    DWORD    offset of new executable (NE,LE,etc) header within disk file,
        or 00000000h if plain MZ executable
---Borland TLINK---
 1Ch  2 BYTEs    ??? (apparently always 01h 00h)
 1Eh    BYTE    signature FBh
 1Fh    BYTE    TLINK version (major in high nybble, minor in low nybble)
 20h  2 BYTEs    ??? (v2.0 apparently always 72h 6Ah, v3.0+ seems always 6Ah 72h)
---ARJ self-extracting archive---
 1Ch  4 BYTEs    signature "RJSX" (older versions, new signature is "aRJsfX" in
        the first 1000 bytes of the file)
---LZEXE 0.90 compressed executable---
 1Ch  4 BYTEs    signature "LZ09"
---LZEXE 0.91 compressed executable---
 1Ch  4 BYTEs    signature "LZ91"
---PKLITE compressed executable---
 1Ch    BYTE    minor version number
 1Dh    BYTE    bits 0-3: major version
        bit 4: extra compression
        bit 5: huge (multi-segment) file
 1Eh  6 BYTEs    signature "PKLITE" (followed by copyright message)
---LHarc 1.x self-extracting archive---
 1Ch  4 BYTEs    unused???
 20h  3 BYTEs    jump to start of extraction code
 23h  2 BYTEs    ???
 25h 12 BYTEs    signature "LHarc's SFX "
---LHA 2.x self-extracting archive---
 1Ch  8 BYTEs    ???
 24h 10 BYTEs    signature "LHa's SFX " (v2.10) or "LHA's SFX " (v2.13)
---TopSpeed C 3.0 CRUNCH compressed file---
 1Ch    DWORD    018A0001h
 20h    WORD    1565h
---PKARCK 3.5 self-extracting archive---
 1Ch    DWORD    00020001h
 20h    WORD    0700h
---BSA (Soviet archiver) self-extracting archive---
 1Ch    WORD    000Fh
 1Eh    BYTE    A7h
---LARC self-extracting archive---
 1Ch  4 BYTEs    ???
 20h 11 BYTEs    "SFX by LARC "
---LH self-extracting archive---
 1Ch  8 BYTEs    ???
 24h  8 BYTEs    "LH's SFX "
---other linkers---
 1Ch    var    optional information
---
  N   N DWORDs    relocation items
Notes:    if word at offset 02h is 4, it should be treated as 00h, since pre-1.10
      versions of the MS linker set it that way
    if both minimum and maximum allocation (offset 0Ah/0Ch) are zero, the
      program is loaded as high in memory as possible
    the maximum allocation is set to FFFFh by default

Format of ROM Module Header:
Offset    Size    Description
 00h  2 BYTEs    ROM signature 55h, AAh
 02h    BYTE    size of ROM in 512-byte blocks
 03h  3 BYTEs    POST initialization entry point (near JMP instruction)
 06h    ROM Program Name List [array]
    Offset    Size    Description
     00h    BYTE    length of ROM program's name (00h if end of name list)
     01h  N BYTEs    program name
     N+1  3 BYTEs    program entry point (near JMP instruction)

Format of new executable header:
Offset    Size    Description
 00h  2 BYTEs    "NE" (4Eh 45h) signature
 02h  2 BYTEs    linker version (major, then minor)
 04h    WORD    offset from start of this header to entry table (see below)
 06h    WORD    length of entry table in bytes
 08h    DWORD    file load CRC (0 in Borland's TPW)
 0Ch    BYTE    program flags
        bits 0-1 DGROUP type
          0 = none
          1 = single shared
          2 = multiple (unshared)
          3 = (null)
        bit 2:    global initialization
        bit 3:    protected mode only
        bit 4:    8086 instructions
        bit 5:    80286 instructions
        bit 6:    80386 instructions
        bit 7:    80x87 instructions
 0Dh    BYTE    application flags
        bits 0-2: application type
            001 full screen (not aware of Windows/P.M. API)
            010 compatible with Windows/P.M. API
            011 uses Windows/P.M. API
        bit 3: is a Family Application (OS/2)
        bit 5: 0=executable, 1=errors in image
        bit 6: non-conforming program (valid stack is not maintained)
        bit 7: DLL or driver rather than application
            (SS:SP info invalid, CS:IP points at FAR init routine
             called with AX=module handle which returns AX=0000h
             on failure, AX nonzero on successful initialization)
 0Eh    WORD    auto data segment index
 10h    WORD    initial local heap size
 12h    WORD    initial stack size (added to data seg, 0000h if SS <> DS)
 14h    DWORD    program entry point (CS:IP), "CS" is index into segment table
 18h    DWORD    initial stack pointer (SS:SP), "SS" is segment index
        if SS=automatic data segment and SP=0000h, the stack pointer is
          set to the top of the automatic data segment, just below the
          local heap
 1Ch    WORD    segment count
 1Eh    WORD    module reference count
 20h    WORD    length of nonresident names table in bytes
 22h    WORD    offset from start of this header to segment table (see below)
 24h    WORD    offset from start of this header to resource table
 26h    WORD    offset from start of this header to resident names table
 28h    WORD    offset from start of this header to module reference table
 2Ah    WORD    offset from start of this header to imported names table
        (array of counted strings, terminated with a string of length
         00h)
 2Ch    DWORD    offset from start of file to nonresident names table
 30h    WORD    count of moveable entry point listed in entry table
 32h    WORD    file alignment size shift count
        0 is equivalent to 9 (default 512-byte pages)
 34h    WORD    number of resource table entries
 36h    BYTE    target operating system
        00h unknown
        01h OS/2
        02h Windows
        03h European MS-DOS 4.x
        04h Windows 386
        05h BOSS (Borland Operating System Services)
 37h    BYTE    other EXE flags
        bit 0: supports long filenames
        bit 1: 2.X protected mode
        bit 2: 2.X proportional font
        bit 3: gangload area
 38h    WORD    offset to return thunks or start of gangload area
 3Ah    WORD    offset to segment reference thunks or length of gangload area
 3Ch    WORD    minimum code swap area size
 3Eh  2 BYTEs    expected Windows version (minor version first)
Note:    this header is documented in detail in the Windows 3.1 SDK Programmer's
      Reference, Vol 4.

Format of Codeview trailer (at end of executable):
Offset    Size    Description
 00h    WORD    signature 4E42h ('NB')
 02h    WORD    Microsoft debug info version number
 04h    DWORD    Codeview header offset

Format of new executable segment table record:
 00h    WORD    offset in file (shift left by alignment shift to get byte offs)
 02h    WORD    length of image in file (0000h = 64K)
 04h    WORD    segment attributes (see below)
 06h    WORD    number of bytes to allocate for segment (0000h = 64K)
Note:    the first segment table entry is entry number 1

Bitfields for segment attributes:
 bit 0    data segment rather than code segment
 bit 1    unused???
 bit 2    real mode
 bit 3    iterated
 bit 4    movable
 bit 5    sharable
 bit 6    preloaded rather than demand-loaded
 bit 7    execute-only (code) or read-only (data)
 bit 8    relocations (directly following code for this segment)
 bit 9    debug info present
 bits 10,11    80286 DPL bits
 bit 12        discardable
 bits 13-15    discard priority

Format of new executable entry table item (list):
Offset    Size    Description
 00h    BYTE    number of entry points (00h if end of entry table list)
 01h    BYTE    segment number (00h if end of entry table list)
 02h 3N BYTEs    entry records
        Offset    Size    Description
         00h    BYTE    flags
                bit 0: exported
                bit 1: single data
                bits 2-7: unused???
         01h    WORD    offset within segment

Format of new executable relocation data (immediately follows segment image):
Offset    Size    Description
 00h    WORD    number of relocation items
 02h 8N BYTEs    relocation items
        Offset    Size    Description
         00h    BYTE    relocation type
                00h LOBYTE
                02h BASE
                03h PTR
                05h OFFS
                0Bh PTR48
                0Dh OFFS32
         01h    BYTE    flags
                bit 2: additive
         02h    WORD    offset within segment
         04h    WORD    target address segment
         06h    WORD    target address offset

Format of new executable resource data:
Offset    Size    Description
 00h    WORD    alignment shift count for resource data
 02h  N RECORDs resources
    Format of resource record:
    Offset    Size    Description
     00h    WORD    type ID
            0000h if end of resource records
            >= 8000h if integer type
            else offset from start of resource table to type string
     02h    WORD    number of resources of this type
     04h    DWORD    reserved for runtime use
     08h  N Resources (see below)
Note:    resource type and name strings are stored immediately following the
      resource table, and are not null-terminated

Format of new executable resource entry:
Offset    Size    Description
 00h    WORD    offset in alignment units from start of file to contents of
        the resource data
 02h    WORD    length of resource image in bytes
 04h    WORD    flags
        bit 4: moveable
        bit 5: shareable
        bit 6: preloaded
 06h    WORD    resource ID
        >= 8000h if integer resource
        else offset from start of resource table to resource string
 08h    DWORD    reserved for runtime use
Notes:    resource type and name strings are stored immediately following the
      resource table, and are not null-terminated
    strings are counted strings, with a string of length 0 indicating the
      end of the resource table

Format of new executable module reference table [one bundle of entries]:
Offset    Size    Description
 00h    BYTE    number of records in this bundle (00h if end of table)
 01h    BYTE    segment indicator
        00h unused
        FFh movable segment, segment number is in entry
        else segment number of fixed segment
 02h  N RECORDs
    Format of segment record
    Offset    Size    Description
     00h    BYTE    flags
            bit 0: entry is exported
            bit 1: entry uses global (shared) data
            bits 7-3: number of parameter words
    ---fixed segment---
     01h    WORD    offset
    ---moveable segment---
     01h  2 BYTEs    INT 3F instruction (CDh 3Fh)
     03h    BYTE    segment number
     05h    WORD    offset
Note:    table entries are numbered starting from 1

Format of new executable resident/nonresident name table entry:
Offset    Size    Description
 00h    BYTE    length of string (00h if end of table)
 01h  N BYTEs    ASCII text of string
 N+1    WORD    ordinal number (index into entry table)
Notes:    the first string in the resident name table is the module name; the
      first entry in the nonresident name table is the module description
    the strings are case-sensitive; if the executable was linked with
      /IGNORECASE, all strings are in uppercase

Format of Linear Executable (enhanced mode executable) header:
Offset    Size    Description
 00h  2 BYTEs    "LE" (4Ch 45h) signature (Windows)
        "LX" (4Ch 58h) signature (OS/2)
 02h    BYTE    byte order (00h = little-endian, nonzero = big-endian)
 03h    BYTE    word order (00h = little-endian, nonzero = big-endian)
 04h    DWORD    executable format level
 08h    WORD    CPU type (see also INT 15/AH=C9h)
        01h Intel 80286 or upwardly compatible
        02h Intel 80386 or upwardly compatible
        03h Intel 80486 or upwardly compatible
        04h Intel Pentium (80586) or upwardly compatible
        20h Intel i860 (N10) or compatible
        21h Intel "N11" or compatible
        40h MIPS Mark I (R2000, R3000) or compatible
        41h MIPS Mark II (R6000) or compatible
        42h MIPS Mark III (R4000) or compatible
 0Ah    WORD    target operating system
        01h OS/2
        02h Windows
        03h European DOS 4.0
        04h Windows 386
 0Ch    DWORD    module version
 10h    DWORD    module type
        bit 2: initialization (only for DLLs)
            0 = global
            1 = per-process
        bit 4: no internal fixups in executable image
        bit 5: no external fixups in executable image
        bits 8,9,10:
            0 = unknown
            1 = incompatible with PM windowing \
            2 = compatible with PM windowing    > (only for
            3 = uses PM windowing API       /    programs)
        bit 13: module not loadable (only for programs)
        bits 17,16,15: module type
            000 program
            001 library (DLL)
            011 protected memory library module
            100 physical device driver
            110 virtual device driver
        bit 30: per-process library termination
            (requires valid CS:EIP, can't be set for .EXE)
 14h    DWORD    number of memory pages
 18h    Initial CS:EIP
    DWORD    object number
    DWORD    offset
 20h    Initial SS:ESP
    DWORD    object number
    DWORD    offset
 28h    DWORD    memory page size
 2Ch    DWORD    (Windows LE) bytes on last page
        (OS/2 LX) page offset shift count
 30h    DWORD    fixup section size
 34h    DWORD    fixup section checksum
 38h    DWORD    loader section size
 3Ch    DWORD    loader section checksum
 40h    DWORD    offset of object table (see below)
 44h    DWORD    object table entries
 48h    DWORD    object page map table offset
 4CH    DWORD    object iterate data map offset
 50h    DWORD    resource table offset
 54h    DWORD    resource table entries
 58h    DWORD    resident names table offset
 5Ch    DWORD    entry table offset
 60h    DWORD    module directives table offset
 64h    DWORD    Module Directives entries
 68h    DWORD    Fixup page table offset
 6Ch    DWORD    Fixup record table offset
 70h    DWORD    imported modules name table offset
 74h    DWORD    imported modules count
 78h    DWORD    imported procedures name table offset
 7Ch    DWORD    per-page checksum table offset
 80h    DWORD    data pages offset
 84h    DWORD    preload page count
 88h    DWORD    non-resident names table offset
 8Ch    DWORD    non-resident names table length
 90h    DWORD    non-resident names checksum
 94h    DWORD    automatic data object
 98h    DWORD    debug information offset
 9Ch    DWORD    debug information length
 A0h    DWORD    preload instance pages number
 A4h    DWORD    demand instance pages number
 A8h    DWORD    extra heap allocation
 ACh 20 BYTEs    reserved
 C0h    WORD    device ID (MS-Windows VxD only)
 C2h    WORD    DDK version (MS-Windows VxD only)
Note:    used by EMM386.EXE, QEMM, and Windows 3.0 Enhanced Mode drivers

Format of object table entry:
Offset    Size    Description
 00h    DWORD    virtual size in bytes
 04h    DWORD    relocation base address
 08h    DWORD    object flags (see below)
 0Ch    DWORD    page map index
 10h    DWORD    page map entries
 14h  4 BYTEs    reserved??? (apparently always zeros)

Bitfields for object flags:
 bit 0    readable
 bit 1    writable
 bit 2    executable
 bit 3    resource
 bit 4    discardable
 bit 5    shared
 bit 6    preloaded
 bit 7    invalid
 bit 8-9 type
    00 normal
    01 zero-filled
    10 resident
    11 resident and contiguous
 bit 10 resident and long-lockable
 bit 11 reserved
 bit 12 16:16 alias required
 bit 13 "BIG" (Huge: 32-bit)
 bit 14 conforming
 bit 15 "OBJECT_I/O_PRIVILEGE_LEVEL"
 bits 16-31 reserved

Format of object page map table entry:
Offset    Size    Description
 00h    BYTE    ??? (usually 00h)
 01h    WORD    (big-endian) index to fixup table
        0000h if no relocation info
 03h    BYTE    type (00h hard copy in file, 03h some relocation needed)

Format of resident names table entry:
Offset    Size    Description
 00h    BYTE    length of name
 01h  N BYTEs    name
 N+1  3 BYTEs    ???

Format of LE linear executable entry table:
Offset    Size    Description
 00h    BYTE    number of entries in table
 01h 10 BYTEs per entry
        Offset    Size    Description
         00h    BYTE    bit flags
                bit 0: non-empty bundle
                bit 1: 32-bit entry
         01h    WORD    object number
         03h    BYTE    entry type flags
                bit 0: exported
                bit 1: uses single data rather than instance
                bit 2: reserved
                bits 3-7: number of stack parameters
         04h    DWORD    offset of entry point
         08h  2 BYTEs    ???
Note:    empty bundles (bit flags at 00h = 00h) are used to skip unused indices,
      and do not contain the remaining nine bytes

Format of LX linear executable entry table [array]:
Offset    Size    Description
 00h    BYTE    number of bundles following (00h = end of entry table)
 01h    BYTE    bundle type
        00h empty
        01h 16-bit entry
        02h 286 callgate entry
        03h 32-bit entry
        04h forwarder entry
        bit 7 set if additional parameter typing information is present
---bundle type 00h---
 no additional fields
---bundle type 01h---
 02h    WORD    object number
 04h    BYTE    entry flags
        bit 0: exported
        bits 7-3: number of stack parameters
 05h    WORD    offset of entry point in object (shifted by page size shift)
---bundle type 02h---
 02h    WORD    object number
 04h    BYTE    entry flags
        bit 0: exported
        bits 7-3: number of stack parameters
 05h    WORD    offset of entry point in object
 07h    WORD    reserved for callgate selector (used by loader)
---bundle type 03h---
 02h    WORD    object number
 04h    BYTE    entry flags
        bit 0: exported
        bits 7-3: number of stack parameters
 05h    DWORD    offset of entry point in object
---bundle type 04h---
 02h    WORD    reserved
 04h    BYTE    forwarder flags
        bit 0: import by ordinal
        bits 7-1 reserved
 05h    WORD    module ordinal
        (forwarder's index into Import Module Name table)
 07h    DWORD    procedure name offset or import ordinal number
Note:    all fields after the first two bytes are repeated N times

Bitfields for linear executable fixup type:
 bit 7    ordinal is BYTE rather than WORD
 bit 6    16-bit rather than 8-bit object number/module ordinal
 bit 5    addition with DWORD rather than WORD
 bit 4    relocation info has size with new two bytes at end
 bit 3    reserved (0)
 bit 2    set if add to destination, clear to replace destination
 bits 1-0    type
        00 internal fixup
        01 external fixup, imported by ordinal
        10 external fixup, imported by name
        11 internal fixup via entry table

Format of linear executable fixup record:
Offset    Size    Description
 00h    BYTE    type
        bits 7-4: modifier (0001 single, 0011 multiple)
        bits 3-0: type
            0000 byte offset
            0010 word segment
            0011 16-bit far pointer (DWORD)
            0101 16-bit offset
            0110 32-bit far pointer (PWORD)
            0111 32-bit offset
            1000 near call or jump, WORD/DWORD based on seg attrib
 01h    BYTE    linear executable fixup type (see above)
---if single type---
 02h    WORD    offset within page
 04h    relocation information
    ---internal fixup---
    BYTE    object number
    ---external,ordinal---
    BYTE    one-based module number in Import Module table
    BYTE/WORD ordinal number
    WORD/DWORD value to add (only present if modifier bit 4 set)
    ---external,name---
    BYTE    one-based module number in Import Module table
    WORD    offset in Import Procedure names
    WORD/DWORD value to add (only present if modifier bit 4 set)
---if multiple type---
 02h    BYTE    number of items
 03h    var    relocation info as for "single" type (see above)
      N WORDs    offsets of items to relocate

Format of old Phar Lap .EXP file header:
Offset    Size    Description
 00h  2 BYTEs    "MP" (4Dh 50h) signature
 02h    WORD    remainder of image size / page size (page size = 512h)
 04h    WORD    size of image in pages
 06h    WORD    number of relocation items
 08h    WORD    header size in paragraphs
 0Ah    WORD    minimum number of extra 4K pages to be allocated at the end
        of program, when it is loaded
 0Ch    WORD    maximum number of extra 4K pages to be allocated at the end
        of program, when it is loaded
 0Eh    DWORD    initial ESP
 12h    WORD    word checksum of file
 14h    DWORD    initial EIP
 18h    WORD    offset of first relocation item
 1Ah    WORD    overlay number
 1Ch    WORD    ??? (wants to be 1)

Format of new Phar Lap .EXP file header:
Offset    Size    Description
 00h  2 BYTEs    signature ("P2" for 286 .EXP executable, "P3" for 386 .EXP)
 02h    WORD    level (01h flat-model file, 02h multisegmented file)
 04h    WORD    header size
 06h    DWORD    file size in bytes
 0Ah    WORD    checksum
 0Ch    DWORD    offset of run-time parameters within file
 10h    DWORD    size of run-time parameters in bytes
 14h    DWORD    offset of relocation table within file
 18h    DWORD    size of relocation table in bytes
 1Ch    DWORD    offset of segment information table within file
 20h    DWORD    size of segment information table in bytes
 24h    WORD    size of segment information table entry in bytes
 26h    DWORD    offset of load image within file
 2Ah    DWORD    size of load image on disk
 2Eh    DWORD    offset of symbol table within file
 32h    DWORD    size of symbol table in bytes
 36h    DWORD    offset of GDT within load image
 3Ah    DWORD    size of GDT in bytes
 3Eh    DWORD    offset of LDT within load image
 42h    DWORD    size of LDT in bytes
 46h    DWORD    offset of IDT within load image
 4Ah    DWORD    size of IDT in bytes
 4Eh    DWORD    offset of TSS within load image
 52h    DWORD    size of TSS in bytes
 56h    DWORD    minimum number of extra bytes to be allocated at end of program
        (level 1 executables only)
 5Ah    DWORD    maximum number of extra bytes to be allocated at end of program
        (level 1 executables only)
 5Eh    DWORD    base load offset (level 1 executables only)
 62h    DWORD    initial ESP
 66h    WORD    initial SS
 68h    DWORD    initial EIP
 6Ch    WORD    initial CS
 6Eh    WORD    initial LDT
 70h    WORD    initial TSS
 72h    WORD    flags
        bit 0: load image is packed
        bit 1: 32-bit checksum is present
        bits 4-2: type of relocation table
 74h    DWORD    memory requirements for load image
 78h    DWORD    32-bit checksum (optional)
 7Ch    DWORD    size of stack segment in bytes
 80h 256 BYTEs    reserved (0)

Format of Phar Lap segment information table entry:
Offset    Size    Description
 00h    WORD    selector number
 02h    WORD    flags
 04h    DWORD    base offset of selector
 08h    DWORD    minimum number of extra bytes to be allocated to the segment

Format of 386|DOS-Extender run-time parameters:
Offset    Size    Description
 00h  2 BYTEs    signature "DX" (44h 58h)
 02h    WORD    minimum number of real-mode params to leave free at run time
 04h    WORD    maximum number of real-mode params to leave free at run time
 06h    WORD    minimum interrupt buffer size in KB
 08h    WORD    maximum interrupt buffer size in KB
 0Ah    WORD    number of interrupt stacks
 0Ch    WORD    size in KB of each interrupt stack
 0Eh    DWORD    offset of byte past end of real-mode code and data
 12h    WORD    size in KB of call buffers
 14h    WORD    flags
        bit 0: file is virtual memory manager
        bit 1: file is a debugger
 16h    WORD    unprivileged flag (if nonzero, executes at ring 1, 2, or 3)
 18h 104 BYTEs    reserved (0)

Format of Phar Lap repeat block header:
Offset    Size    Description
 00h    WORD    byte count
 02h    BYTE    repeat string length

Format of Borland debugging information header (following load image):
Offset    Size    Description
 00h    WORD    signature 52FBh
 02h    WORD    version ID
 04h    DWORD    size of name pool in bytes
 08h    WORD    number of names in namem pool
 0Ah    WORD    number of type entries
 0Ch    WORD    number of structure members
 0Eh    WORD    number of symbols
 10h    WORD    number of global symbols
 12h    WORD    number of modules
 14h    WORD    number of locals (optional)
 16h    WORD    number of scopes in table
 18h    WORD    number of line-number entries
 1Ah    WORD    number of include files
 1Ch    WORD    number of segment records
 1Eh    WORD    number of segment/file correlations
 20h    DWORD    size of load image after removing uninitialized data and debug
        info
 24h    DWORD    debugger hook; pointer into debugged program whose meaning
        depends on program flags
 28h    BYTE    program flags
        bit 0: case-sensitive link
        bit 1: pascal overlay program
 29h    WORD    no longer used
 2Bh    WORD    size of data pool in bytes
 2Dh    BYTE    padding
 2Eh    WORD    size of following header extension (currently 00h, 10h, or 20h)
 30h    WORD    number of classes
 32h    WORD    number of parents
 34h    WORD    number of global classes (currently unused)
 36h    WORD    number of overloads (currently unused)
 38h    WORD    number of scope classes
 3Ah    WORD    number of module classes
 3Ch    WORD    number of coverage offsets
 3Eh    DWORD    offset relative to symbol base of name pool
 42h    WORD    number of browser information records
 44h    WORD    number of optimized symbol records
 46h    WORD    debugging flags
 48h  8 BYTEs    padding
Note:    additional information on the Borland debugging info may be found in
      Borland's Open Architecture Handbook
--------U-214B-------------------------------
INT 21 - ELRES v1.0 only - INSTALLATION CHECK
    AH = 4Bh
    DS:DX = 0000h:0000h
Return: ES:BX -> ELRES history structure (see AH=2Bh/CX=454Ch)
    DX = DABEh (signature, DAve BEnnett)
Program: ELRES is an MS-DOS return code (errorlevel) recorder by David H.
      Bennett
SeeAlso: AH=2Bh/CX=454Ch
--------v-214B04-----------------------------
INT 21 - VIRUS - "MG", "699"/"Thirteen Minutes" - INSTALLATION CHECK
    AX = 4B04h
Return: CF clear if "MG" resident
    AX = 044Bh if "699"/"Thirteen Minutes" resident
SeeAlso: AX=4243h,AX=4B21h
--------D-214B05-----------------------------
INT 21 - DOS 5+ - SET EXECUTION STATE
    AX = 4B05h
    DS:DX -> execution state structure (see below)
Return: CF clear if successful
        AX = 0000h
    CF set on error
        AX = error code (see AH=59h)
Note:    used by programs which intercept AX=4B00h to prepare new programs for
      execution (including setting the DOS version number).     No DOS, BIOS
      or other software interrupt may be called after return from this call
      before commencement of the child process.  If DOS is running in the
      HMA, A20 is turned off on return from this call.
SeeAlso: AH=4Bh

Format of execution state structure:
Offset    Size    Description
 00h    WORD    reserved (00h)
 02h    WORD    type flags
        bit 0: program is an .EXE
        bit 1: program is an overlay
 04h    DWORD    pointer to ASCIZ name of program file
 08h    WORD    PSP segment of new program
 0Ah    DWORD    starting CS:IP of new program
 0Eh    DWORD    program size including PSP
--------v-214B20-----------------------------
INT 21 - VIRUS - "Holocaust"/"Telefonica" - ???
    AX = 4B20h
SeeAlso: AX=4B04h,AX=4B21h
--------v-214B21-----------------------------
INT 21 C - VIRUS - "Holocaust"/"Telefonica" - ???
    AX = 4B21h
Note:    called at completion of virus installation
SeeAlso: AX=4B04h,AX=4B20h,AX=4B25h
--------v-214B25-----------------------------
INT 21 - VIRUS - "1063"/"Mono" - INSTALLATION CHECK
    AX = 4B25h
Return: DI = 1234h if resident
SeeAlso: AX=4B21h,AX=4B40h
--------v-214B40-----------------------------
INT 21 - VIRUS - "Plastique"/"AntiCad" - INSTALLATION CHECK
    AX = 4B40h
Return: AX = 5678h if resident
SeeAlso: AX=4B25h,AX=4B41h,AX=4B4Ah
--------v-214B41-----------------------------
INT 21 - VIRUS - "Plastique"/"AntiCad" - ???
    AX = 4B41h
    ???
Return: ???
SeeAlso: AX=4B40h
--------v-214B4A-----------------------------
INT 21 - VIRUS - "Jabberwocky" - INSTALLATION CHECK
    AX = 4B4Ah
Return: AL = 57h if resident
SeeAlso: AX=4B40h,AX=4B4Bh
--------v-214B4B-----------------------------
INT 21 - VIRUS - "Horse-2" - INSTALLATION CHECK
    AX = 4B4Bh
Return: CF clear if resident
SeeAlso: AX=4B4Ah,AX=4B4Dh
--------v-214B4D-----------------------------
INT 21 - VIRUS - "Murphy-2", "Patricia"/"Smack" - INSTALLATION CHECK
    AX = 4B4Dh
Return: CF clear if resident
SeeAlso: AX=4B4Ah,AX=4B50h
--------v-214B50-----------------------------
INT 21 - VIRUS - "Plastique-2576"/"AntiCad-2576" - INSTALLATION CHECK
    AX = 4B50h
Return: AX = 1234h if resident
SeeAlso: AX=4B4Dh,AX=4B53h,AX=4B60h
--------v-214B53-----------------------------
INT 21 - VIRUS - "Horse" - INSTALLATION CHECK
    AX = 4B53h
Return: CF clear if resident
SeeAlso: AX=4B50h,AX=4B55h
--------v-214B55-----------------------------
INT 21 - VIRUS - "Sparse" - INSTALLATION CHECK
    AX = 4B55h
Return: AX = 1231h if resident
SeeAlso: AX=4B53h,AX=4B59h
--------v-214B59-----------------------------
INT 21 - VIRUS - "Murphy-1", "Murphy-4" - INSTALLATION CHECK
    AX = 4B59h
Return: CF clear if resident
SeeAlso: AX=4B50h,AX=4B5Eh
--------v-214B5E-----------------------------
INT 21 - VIRUS - "Brothers" - INSTALLATION CHECK
    AX = 4B5Eh
Return: CF clear if resident
SeeAlso: AX=4B59h,AX=4B87h
--------v-214B60-----------------------------
INT 21 - VIRUS - "Plastique-2576"/"AntiCad-2576" - ???
    AX = 4B60h
    ???
Return: ???
SeeAlso: AX=4B50h
--------v-214B87-----------------------------
INT 21 - VIRUS - "Shirley" - INSTALLATION CHECK
    AX = 4B87h
Return: AX = 6663h if resident
SeeAlso: AX=4B5Eh,AX=4B95h
--------v-214B95-----------------------------
INT 21 - VIRUS - "Zherkov-1882" - INSTALLATION CHECK
    AX = 4B95h
Return: AX = 1973h if resident
SeeAlso: AX=4B87h,AX=4BA7h
--------v-214BA7-----------------------------
INT 21 - VIRUS - "1876"/"Dash-em" - INSTALLATION CHECK
    AX = 4BA7h
Return: AX = B459h if resident
SeeAlso: AX=4B95h,AX=4BAAh
--------v-214BAA-----------------------------
INT 21 - VIRUS - "Nomenklatura" - INSTALLATION CHECK
    AX = 4BAAh
Return: CF clear if resident
SeeAlso: AX=4BA7h,AX=4BAFh
--------v-214BAF-----------------------------
INT 21 - VIRUS - "948"/"Screenplus1", "Magnitogorsk" - INSTALLATION CHECK
    AX = 4BAFh
Return: AL = AFh if "Magnitogorsk" resident
    AL = FAh if "948"/"Screenplus1" resident
SeeAlso: AX=4BAAh,AX=4BDDh
--------v-214BDD-----------------------------
INT 21 - VIRUS - "Lozinsky"/"Zherkov" - INSTALLATION CHECK
    AX = 4BDDh
Return: AX = 1234h
SeeAlso: AX=4BAFh,AX=4BFEh
--------v-214BEE-----------------------------
INT 21 - F-DRIVER.SYS v1.14+ - GRAB INT 21
    AX = 4BEEh
Return: AX = 1234h if grab successful
       = 2345h if failed (INT 21 grabbed previously)
Notes:    F-DRIVER.SYS is part of the F-PROT virus/trojan protection package by
      Fridrik Skulason
    when called the first time, this function moves the INT 21 monitoring
      code from its original location in the INT 21 chain to be the first
      thing called by INT 21.  This is the mechanism used by F-NET.
SeeAlso: INT 2F/AX=4653h
--------k-214BF0-----------------------------
INT 21 - DIET v1.10+ (Overlay Mode) - INSTALLATION CHECK
    AX = 4BF0h
Return: CF clear if installed
        AX = 899Dh
Program: DIET is an executable-compression program by Teddy Matsumoto
SeeAlso: AX=37D0h,AX=4BF1h
--------k-214BF1-----------------------------
INT 21 - DIET v1.10+ (Overlay Mode) - EXPAND PROGRAM???
    AX = 4BF1h
Return: ???
SeeAlso: AX=37D0h,AX=4BF0h
--------v-214BFE-----------------------------
INT 21 - VIRUS - "Hitchcock", "Dark Avenger-1028", "1193" - INSTALLATION CHECK
    AX = 4BFEh
Return: AX = 1234h if "Hitchcock" resident
    AX = ABCDh if "1193"/"Copyright" resident
    DI = 55BBh if "Dark Avenger-1028" resident
SeeAlso: AX=4BDDh,AX=4BFFh"Justice"
--------v-214BFF-----------------------------
INT 21 - VIRUS - "USSR-707", "Justice", "Europe 92" - INSTALLATION CHECK
    AX = 4BFFh
Return: BL = FFh if "USSR-707" resident
    DI = 55AAh if "Justice" resident
    CF clear if "Europe 92" resident
SeeAlso: AX=4BFEh,AX=4BFFh"Cascade",AX=5252h
--------v-214BFFSI0000-----------------------
INT 21 - VIRUS - "Cascade" - INSTALLATION CHECK
    AX = 4BFFh
    SI = 0000h
    DI = 0000h
Return: DI = 55AAh if installed
SeeAlso: AX=4BFFh"Justice",AX=5252h
--------D-214C-------------------------------
INT 21 - DOS 2+ - "EXIT" - TERMINATE WITH RETURN CODE
    AH = 4Ch
    AL = return code
Return: never returns
Notes:    unless the process is its own parent (see AH=26h, offset 16h in PSP),
      all open files are closed and all memory belonging to the process
      is freed
    all network file locks should be removed before calling this function
SeeAlso: AH=00h,AH=26h,AH=4Bh,AH=4Dh,INT 15/AH=12h/BH=02h,INT 20,INT 22
SeeAlso: INT 60/DI=0601h
----------214C57-----------------------------
INT 21 - Headroom - ???
    AX = 4C57h
    DS:DX -> target address
Note:    jumps to target address instead of terminating program
SeeAlso: AX=5758h
--------D-214D-------------------------------
INT 21 - DOS 2+ - GET RETURN CODE (ERRORLEVEL)
    AH = 4Dh
Return: AH = termination type
        00h normal (INT 20,INT 21/AH=00h, or INT 21/AH=4Ch)
        01h control-C abort
        02h critical error abort
        03h terminate and stay resident (INT 21/AH=31h or INT 27)
    AL = return code
Notes:    the word in which DOS stores the return code is cleared after being
      read by this function, so the return code can only be retrieved once
    COMMAND.COM stores the return code of the last external command it
      executed as ERRORLEVEL
    this call should not be used if the child was started with AX=4B04h;
      use AH=8Ah instead
    the following sequence will close a Virtual DOS Machine under OS/2 2.0:
      MOV    AH,4Dh
      INT    21h
      HLT
      DB    02h,0FDh
      This sequence is the only way to close a specific VDM which was
      booted from floppy or a disk image.
SeeAlso: AH=4Bh,AH=4Ch,AH=8Ah
--------D-214E-------------------------------
INT 21 - DOS 2+ - "FINDFIRST" - FIND FIRST MATCHING FILE
    AH = 4Eh
    AL = special flag for use by APPEND (see note below)
    CX = file attribute mask (see AX=4301h) (bits 0 and 5 ignored)
        0088h (Novell DOS 7) find first deleted file
    DS:DX -> ASCIZ file specification (may include path and wildcards)
Return: CF clear if successful
        [DTA] = FindFirst data block (see below)
    CF set on error
        AX = error code (02h,03h,12h) (see AH=59h)
Notes:    for search attributes other than 08h, all files with at MOST the
      specified combination of hidden, system, and directory attributes
      will be returned.  Under DOS 2.x, searching for attribute 08h
      (volume label) will also return normal files, while under DOS 3+
      only the volume label (if any) will be returned.
    this call also returns successfully if given the name of a character
      device without wildcards.  DOS 2.x returns attribute 00h, size 0,
      and the current date and time.  DOS 3+ returns attribute 40h and the
      current date and time.
    immediately after an INT 2F/AX=B711h (APPEND return found name), the
      name at DS:DX will be overwritten; if AL=00h on entry, the actual
      found pathname will be stored, otherwise, the actual found path
      will be prepended to the original filespec without a path.
    under LANtastic, this call may be used to obtain a list of a server's
      shared resources by searching for "\\SERVER\*.*"; a list of printer
      resources may be obtained by searching for "\\SERVER\@*.*"
    under the FlashTek X-32 DOS extender, the filespec pointer is in DS:EDX
BUGS:    under DOS 3.x and 4.x, the second and subsequent calls to this function
      with a character device name (no wildcards) and search attributes
      which include the volume-label bit (08h) will fail unless there is
      an intervening DOS call which implicitly or explicity performs a
      directory search without the volume-label bit.  Such implicit
      searches are performed by CREATE (AH=3Ch), OPEN (AH=3Dh), UNLINK
      (AH=41h), and RENAME (AH=56h)
    DR-DOS 3.41 and 5.0 return the Directory attribute for the volume label
SeeAlso: AH=11h,AH=4Fh,AX=4301h,INT 2F/AX=111Bh,INT 2F/AX=B711h

Format of FindFirst data block:
Offset    Size    Description
---PC-DOS 3.10, PC-DOS 4.01, MS-DOS 3.2/3.3/5.0---
 00h    BYTE    drive letter (bits 0-6), remote if bit 7 set
 01h 11 BYTEs    search template
 0Ch    BYTE    search attributes
---DOS 2.x (and some DOS 3.x???)---
 00h    BYTE    search attributes
 01h    BYTE    drive letter
 02h 11 BYTEs    search template
---WILDUNIX.COM---
 00h 12 BYTEs    15-character wildcard search pattern and drive letter (packed)
 0Ch    BYTE    search attributes
---DOS 2.x and most 3.x---
 0Dh    WORD    entry count within directory
 0Fh    DWORD    pointer to DTA???
 13h    WORD    cluster number of start of parent directory
---PC-DOS 4.01, MS-DOS 3.2/3.3/5.0---
 0Dh    WORD    entry count within directory
 0Fh    WORD    cluster number of start of parent directory
 11h  4 BYTEs    reserved
---all versions, documented fields---
 15h    BYTE    attribute of file found
 16h    WORD    file time
            bits 11-15: hour
            bits 5-10:    minute
            bits 0-4:    seconds/2
 18h    WORD    file date
            bits 9-15:    year-1980
            bits 5-8:    month
            bits 0-4:    day
 1Ah    DWORD    file size
 1Eh 13 BYTEs    ASCIZ filename+extension
--------f-214E-------------------------------
INT 21 - WILDUNIX.COM internal - INSTALLATION CHECK
    AH = 4Eh
    DS:DX = 0000h:0000h
Return: AH = 99h if installed
Program: WILDUNIX.COM is a resident Unix-style wildcard expander by Steve
      Hosgood and Terry Barnaby
--------D-214F-------------------------------
INT 21 - DOS 2+ - "FINDNEXT" - FIND NEXT MATCHING FILE
    AH = 4Fh
    [DTA] = data block from previous FindFirst or FindNext call
Return: CF clear if successful
    CF set on error
        AX = error code (12h) (see AH=59h)
Note:    under Novell DOS 7, if the FindFirst call (AH=4Eh) had CX=0088h, then
      the next matching deleted file will be returned
BUG:    DR-DOS 3.41 and 5.0 return the Directory attribute for the volume label
SeeAlso: AH=12h,AH=4Eh
--------D-2150-------------------------------
INT 21 - DOS 2+ internal - SET CURRENT PROCESS ID (SET PSP ADDRESS)
    AH = 50h
    BX = segment of PSP for new process
Notes:    DOS uses the current PSP address to determine which processes own files
      and memory; it corresponds to process identifiers used by other OSs
    under DOS 2.x, this function cannot be invoked inside an INT 28h
      handler without setting the Critical Error flag
    under MS-DOS 3+ and DR-DOS 3.41+, this function does not use any of
      the DOS-internal stacks and may thus be called at any time, even
      during another INT 21h call
    some Microsoft applications such as Quick C 2.51 use segments of 0000h
      and FFFFh and direct access to the SDA (see AX=5D06h) to test whether
      they are running under MS-DOS rather than a compatible OS; although
      one should only call this function with valid PSP addresses, any
      program hooking it should be prepared to handle invalid addresses
    supported by OS/2 compatibility box
    this call was undocumented prior to the release of DOS 5.0
SeeAlso: AH=26h,AH=51h,AH=62h
--------D-2151-------------------------------
INT 21 - DOS 2+ internal - GET CURRENT PROCESS ID (GET PSP ADDRESS)
    AH = 51h
Return: BX = segment of PSP for current process
Notes:    DOS uses the current PSP address to determine which processes own files
      and memory; it corresponds to process identifiers used by other OSs
    under DOS 2.x, this function cannot be invoked inside an INT 28h
      handler without setting the Critical Error flag
    under DOS 3+, this function does not use any of the DOS-internal stacks
      and may thus be called at any time, even during another INT 21h call
    supported by OS/2 compatibility box
    identical to the documented AH=62h
    this call was undocumented prior to the release of DOS 5.0
SeeAlso: AH=26h,AH=50h,AH=62h
--------D-2152-------------------------------
INT 21 U - DOS 2+ internal - "SYSVARS" - GET LIST OF LISTS
    AH = 52h
Return: ES:BX -> DOS list of lists
Notes:    partially supported by OS/2 v1.1 compatibility box (however, most
      pointers are FFFFh:FFFFh, LASTDRIVE is FFh, and the NUL header "next"
      pointer is FFFFh:FFFFh).
    on return, ES points at the DOS data segment (see also INT 2F/AX=1203h)
SeeAlso: INT 2F/AX=1203h

Format of List of Lists:
Offset    Size    Description
 -24    WORD    (DOS 3.1+) contents of CX from INT 21/AX=5E01h
 -22    WORD    (DOS ???+) LRU counter for FCB caching
 -20    WORD    (DOS ???+) LRU counter for FCB opens
 -18    DWORD    (DOS ???+) address of OEM function handler (see INT 21/AH=F8h)
            FFFFh:FFFFh if not installed or not available
 -14    WORD    (DOS ???+) offset in DOS CS of code to return from INT 21 call
 -12    WORD    (DOS 3.1+) sharing retry count (see AX=440Bh)
 -10    WORD    (DOS 3.1+) sharing retry delay (see AX=440Bh)
 -8    DWORD    (DOS 3+) pointer to current disk buffer
 -4    WORD    (DOS 3+) pointer in DOS code segment of unread CON input
        when CON is read via a handle, DOS reads an entire line,
          and returns the requested portion, buffering the rest
          for the next read.  0000h indicates no unread input
 -2    WORD    segment of first memory control block
 00h    DWORD    pointer to first Drive Parameter Block (see AH=32h)
 04h    DWORD    pointer to first System File Table (see below)
 08h    DWORD    pointer to active CLOCK$ device's header (most recently loaded
        driver with CLOCK bit set)
 0Ch    DWORD    pointer to active CON device's header (most recently loaded
        driver with STDIN bit set)
---DOS 2.x---
 10h    BYTE    number of logical drives in system
 11h    WORD    maximum bytes/block of any block device
 13h    DWORD    pointer to first disk buffer (see below)
 17h 18 BYTEs    actual NUL device driver header (not a pointer!)
        NUL is always the first device on DOS's linked list of device
        drivers. (see below)
---DOS 3.0---
 10h    BYTE    number of block devices
 11h    WORD    maximum bytes/block of any block device
 13h    DWORD    pointer to first disk buffer (see below)
 17h    DWORD    pointer to array of current directory structures (see below)
 1Bh    BYTE    value of LASTDRIVE command in CONFIG.SYS (default 5)
 1Ch    DWORD    pointer to STRING= workspace area
 20h    WORD    size of STRING area (the x in STRING=x from CONFIG.SYS)
 22h    DWORD    pointer to FCB table
 26h    WORD    the y in FCBS=x,y from CONFIG.SYS
 28h 18 BYTEs    actual NUL device driver header (not a pointer!)
        NUL is always the first device on DOS's linked list of device
        drivers. (see below)
---DOS 3.1-3.3---
 10h    WORD    maximum bytes per sector of any block device
 12h    DWORD    pointer to first disk buffer in buffer chain (see below)
 16h    DWORD    pointer to array of current directory structures (see below)
 1Ah    DWORD    pointer to system FCB tables (see below)
 1Eh    WORD    number of protected FCBs (the y in the CONFIG.SYS FCBS=x,y)
 20h    BYTE    number of block devices installed
 21h    BYTE    number of available drive letters (largest of 5, installed
        block devices, and CONFIG.SYS LASTDRIVE=).  Also size of
        current directory structure array.
 22h 18 BYTEs    actual NUL device driver header (not a pointer!)
        NUL is always the first device on DOS's linked list of device
        drivers. (see below)
 34h    BYTE    number of JOIN'ed drives
---DOS 4.x---
 10h    WORD    maximum bytes per sector of any block device
 12h    DWORD    pointer to disk buffer info record (see below)
 16h    DWORD    pointer to array of current directory structures (see below)
 1Ah    DWORD    pointer to system FCB tables (see below)
 1Eh    WORD    number of protected FCBs (the y in the CONFIG.SYS FCBS=x,y)
        (always 00h for DOS 5.0)
 20h    BYTE    number of block devices installed
 21h    BYTE    number of available drive letters (largest of 5, installed
        block devices, and CONFIG.SYS LASTDRIVE=).  Also size of
        current directory structure array.
 22h 18 BYTEs    actual NUL device driver header (not a pointer!)
        NUL is always the first device on DOS's linked list of device
        drivers. (see below)
 34h    BYTE    number of JOIN'ed drives
 35h    WORD    pointer within IBMDOS code segment to list of special program
        names (see below)
        (always 0000h for DOS 5.0)
 37h    DWORD    pointer to FAR routine for resident IFS utility functions
        (see below)
        may be called by any IFS driver which does not wish to
        service functions 20h or 24h-28h itself
 3Bh    DWORD    pointer to chain of IFS (installable file system) drivers
 3Fh    WORD    the x in BUFFERS x,y (rounded up to multiple of 30 if in EMS)
 41h    WORD    number of lookahead buffers (the y in BUFFERS x,y)
 43h    BYTE    boot drive (1=A:)
 44h    BYTE    flag: 01h to use DWORD moves (80386+), 00h otherwise
 45h    WORD    extended memory size in KB
---DOS 5.0-6.0---
 10h 39 BYTEs    as for DOS 4.x (see above)
 37h    DWORD    pointer to SETVER program list or 0000h:0000h
 3Bh    WORD    (DOS=HIGH) offset in DOS CS of function to fix A20 control
        when executing special .COM format
 3Dh    WORD    PSP of most-recently EXECed program if DOS in HMA, 0000h if low
 3Fh  8 BYTEs    as for DOS 4.x (see above)

Format of memory control block (see also below):
Offset    Size    Description
 00h    BYTE    block type: 5Ah if last block in chain, otherwise 4Dh
 01h    WORD    PSP segment of owner or
        0000h if free
        0006h if DR-DOS XMS UMB
        0007h if DR-DOS excluded upper memory ("hole")
        0008h if belongs to DOS
        FFFAh if 386MAX UMB control block (see AX=4402h"386MAX")
        FFFDh if 386MAX locked-out memory
        FFFEh if 386MAX UMB (immediately follows its control block)
        FFFFh if 386MAX 6.01 device driver
 03h    WORD    size of memory block in paragraphs
 05h  3 BYTEs    unused by MS-DOS
        (386MAX) if locked-out block, region start/prev region end
---DOS 2.x,3.x---
 08h  8 BYTEs    unused
---DOS 4+ ---
 08h  8 BYTEs    ASCII program name if PSP memory block or DR-DOS UMB,
          else garbage
        null-terminated if less than 8 characters
Notes:    the next MCB is at segment (current + size + 1)
    under DOS 3.1+, the first memory block is the DOS data segment,
      containing installable drivers, buffers, etc.     Under DOS 4+ it is
      divided into subsegments, each with its own memory control block
      (see below), the first of which is at offset 0000h.
    for DOS 5+, blocks owned by DOS may have either "SC" or "SD" in bytes
      08h and 09h.    "SC" is system code or locked-out inter-UMB memory,
      "SD" is system data, device drivers, etc.
    Some versions of DR-DOS use only seven characters of the program name,
      placing a NUL in the eighth byte.

Format of MS-DOS 5+ UMB control block:
Offset    Size    Description
 00h    BYTE    type: 5Ah if last block in chain, 4Dh otherwise
 01h    WORD    first available paragraph in UMB if control block at start
        of UMB, 000Ah if control block at end of UMB
 03h    WORD    length in paragraphs of following UMB or locked-out region
 05h  3 BYTEs    unused
 08h  8 BYTEs    block type name: "UMB" if start block, "SM" if end block in UMB

Format of STARLITE (General Software's Embedded DOS) memory control block:
Offset    Size    Description
 00h    BYTE    block type: 5Ah if last block in chain, otherwise 4Dh
 01h    WORD    PSP segment of owner, 0000h if free, 0008h if belongs to DOS
 03h    WORD    size of memory block in paragraphs
 05h    BYTE    unused
 06h    WORD    segment address of next memory control block (0000h if last)
 08h    WORD    segment address of previous memory control block or 0000h
 0Ah  6 BYTEs    reserved

Format of DOS 4+ data segment subsegment control blocks:
Offset    Size    Description
 00h    BYTE    subsegment type (blocks typically appear in this order)
        "D"  device driver
        "E"  device driver appendage
        "I"  IFS (Installable File System) driver
        "F"  FILES=  control block storage area (for FILES>5)
        "X"  FCBS=   control block storage area, if present
        "C"  BUFFERS EMS workspace area (if BUFFERS /X option used)
        "B"  BUFFERS=  storage area
        "L"  LASTDRIVE=     current directory structure array storage area
        "S"  STACKS=  code and data area, if present (see below)
        "T"  INSTALL= transient code
 01h    WORD    paragraph of subsegment start (usually the next paragraph)
 03h    WORD    size of subsegment in paragraphs
 05h  3 BYTEs    unused
 08h  8 BYTEs    for types "D" and "I", base name of file from which the driver
          was loaded (unused for other types)

Format of data at start of STACKS code segment (if present):
Offset    Size    Description
 00h    WORD    ???
 02h    WORD    number of stacks (the x in STACKS=x,y)
 04h    WORD    size of stack control block array (should be 8*x)
 06h    WORD    size of each stack (the y in STACKS=x,y)
 08h    DWORD    pointer to STACKS data segment
 0Ch    WORD    offset in STACKS data segment of stack control block array
 0Eh    WORD    offset in STACKS data segment of last element of that array
 10h    WORD    offset in STACKS data segment of the entry in that array for
        the next stack to be allocated (initially same as value in 0Eh
        and works its way down in steps of 8 to the value in 0Ch as
        hardware interrupts pre-empt each other)
Note:    the STACKS code segment data may, if present, be located as follows:
    DOS 3.2:    The code segment data is at a paragraph boundary fairly early
        in the IBMBIO segment (seen at 0070:0190h)
    DOS 3.3:    The code segment is at a paragraph boundary in the DOS data
        segment, which may be determined by inspecting the segment
        pointers of the vectors for those of interrupts 02h, 08h-0Eh,
        70h, 72-77h which have not been redirected by device drivers or
        TSRs.
    DOS 4+    Identified by sub-segment control block type "S" within the DOS
        data segment.
SeeAlso: INT B4"STACKMAN"

Format of array elements in STACKS data segment:
Offset    Size    Description
 00h    BYTE    status: 00h=free, 01h=in use, 03h=corrupted by overflow of
        higher stack.
 01h    BYTE    not used
 02h    WORD    previous SP
 04h    WORD    previous SS
 06h    WORD    ptr to word at top of stack (new value for SP). The word at the
        top of the stack is preset to point back to this control block.

SHARE.EXE hooks (DOS 3.1-6.00):
(offsets from first system file table--pointed at by ListOfLists+04h)
Offset    Size    Description
-3Ch    DWORD    pointer to FAR routine for ???
        Note: not called by MS-DOS 3.3, set to 0000h:0000h by
            SHARE 3.3+
-38h    DWORD    pointer to FAR routine called on opening file
        on call, internal DOS location points at filename(see AX=5D06h)
        Return: CF clear if successful
            CF set on error
                AX = DOS error code (24h) (see AH=59h)
        Note: SHARE directly accesses DOS-internal data to get name of
            file just opened
-34h    DWORD    pointer to FAR routine called on closing file
        ES:DI -> system file table
        Note: does something to every Record Lock Record for file
-30h    DWORD    pointer to FAR routine to close all files for given computer
        (called by AX=5D03h)
-2Ch    DWORD    pointer to FAR routine to close all files for given process
        (called by AX=5D04h)
-28h    DWORD    pointer to FAR routine to close file by name
        (called by AX=5D02h)
        DS:SI -> DOS parameter list (see AX=5D00h)
           DPL's DS:DX -> name of file to close
        Return: CF clear if successful
            CF set on error
                AX = DOS error code (03h) (see AH=59h)
-24h    DWORD    pointer to FAR routine to lock region of file
        call with BX = file handle
              ---DOS 3.x---
              CX:DX = starting offset
              SI:AX = size
              ---DOS 4+---
              DS:DX -> lock range
                    DWORD start offset
                    DWORD size in bytes
        Return: CF set on error
                AL = DOS error code (21h) (see AH=59h)
        Note: not called if file is marked as remote
-20h    DWORD    pointer to FAR routine to unlock region of file
        call with BX = file handle
              ---DOS 3.x---
              CX:DX = starting offset
              SI:AX = size
              ---DOS 4+---
              DS:DX -> lock range
                    DWORD start offset
                    DWORD size in bytes
        Return: CF set on error
                AL = DOS error code (21h) (see AH=59h)
        Note: not called if file is marked as remote
-1Ch    DWORD    pointer to FAR routine to check if file region is locked
        call with ES:DI -> system file table entry for file
            CX = length of region from current position in file
        Return: CF set if any portion of region locked
                AX = 0021h
-18h    DWORD    pointer to FAR routine to get open file list entry
        (called by AX=5D05h)
        call with DS:SI -> DOS parameter list (see AX=5D00h)
            DPL's BX = index of sharing record
            DPL's CX = index of SFT in SFT chain of sharing rec
        Return: CF set on error or not loaded
                AX = DOS error code (12h) (see AH=59h)
            CF clear if successful
                ES:DI -> filename
                CX = number of locks owned by specified SFT
                BX = network machine number
                DX destroyed
-14h    DWORD    pointer to FAR routine for updating FCB from SFT???
        call with DS:SI -> unopened FCB
              ES:DI -> system file table entry
        Return: BL = C0h???
        Note: copies following fields from SFT to FCB:
           starting cluster of file      0Bh     1Ah
           sharing record offset      33h     1Ch
           file attribute          04h     1Eh
-10h    DWORD    pointer to FAR routine to get first cluster of FCB file ???
        call with ES:DI -> system file table entry
              DS:SI -> FCB
        Return: CF set if SFT closed or sharing record offsets
                mismatched
            CF clear if successful
                BX = starting cluster number from FCB
-0Ch    DWORD    pointer to FAR routine to close file if duplicate for process
        DS:SI -> system file table
        Return: AX = number of handle in JFT which already uses SFT
        Note: called during open/create of a file
        Note: if SFT was opened with inheritance enabled and sharing
            mode 111, does something to all other SFTs owned by
            same process which have the same file open mode and
            sharing record
-08h    DWORD    pointer to FAR routine for closing file
        Note: closes various handles referring to file most-recently
            opened
-04h    DWORD    pointer to FAR routine to update directory info in related SFT
          entries
        call with ES:DI -> system file table entry for file (see below)
              AX = subfunction (apply to each related SFT)
                00h: update time stamp (offset 0Dh) and date
                     stamp (offset 0Fh)
                01h: update file size (offset 11h) and starting
                     cluster (offset 0Bh).  Sets last-accessed
                     cluster fields to start of file if file
                     never accessed
                02h: as function 01h, but last-accessed fields
                     always changed
                03h: do both functions 00h and 02h
        Note: follows ptr at offset 2Bh in system file table entries
        Note: NOP if opened with no-inherit or via FCB
Notes:    most of the above hooks (except -04h, -14h, -18h, and -3Ch) assume
      either that SS=DOS DS or SS=DS=DOS DS and directly access
      DOS-internal data
    sharing hooks are not supported by DR-DOS 5-6; will reportedly be
      supported by Novell DOS 7

Format of sharing record:
Offset    Size    Description
 00h    BYTE    flag
        00h free block
        01h allocated block
        FFh end marker
 01h    WORD    size of block
 03h    BYTE    checksum of pathname (including NUL)
        if sum of ASCII values is N, checksum is (N/256 + N%256)
 04h    WORD    offset in SHARE's DS of first Record Lock Record (see below)
 06h    DWORD    pointer to start of system file table chain for file
 0Ah    WORD    unique sequence number
 0Ch    var    ASCIZ full pathname
Note:    not supported by DR-DOS SHARE 1.1 and 2.0; will reportedly be
      supported by Novell DOS 7

Format of Record Lock Record (SHARE.EXE):
Offset    Size    Description
 00h    WORD    offset in SHARE's DS of next lock table in list or 0000h
 02h    DWORD    offset in file of start of locked region
 06h    DWORD    offset in file of end of locked region
 0Ah    DWORD    pointer to System File Table entry for this file
 0Eh    WORD    PSP segment of lock's owner
---DOS 5+ ---
 10h    WORD    lock type: (00h lock all, 01h lock writes only)

Format of DOS 2.x system file tables:
Offset    Size    Description
 00h    DWORD    pointer to next file table (offset FFFFh if last)
 04h    WORD    number of files in this table
 06h  28h bytes per file
    Offset    Size    Description
     00h    BYTE    number of file handles referring to this file
     01h    BYTE    file open mode (see AH=3Dh)
     02h    BYTE    file attribute
     03h    BYTE    drive (0 = character device, 1 = A, 2 = B, etc)
     04h 11 BYTEs    filename in FCB format (no path,no period,blank-padded)
     0Fh    WORD    ???
     11h    WORD    ???
     13h    DWORD    file size???
     17h    WORD    file date in packed format (see AX=5700h)
     19h    WORD    file time in packed format (see AX=5700h)
     1Bh    BYTE    device attribute (see AX=4400h)
    ---character device---
     1Ch    DWORD    pointer to device driver
    ---block device---
     1Ch    WORD    starting cluster of file
     1Eh    WORD    relative cluster in file of last cluster accessed
    ------
     20h    WORD    absolute cluster number of current cluster
     22h    WORD    ???
     24h    DWORD    current file position???

Format of DOS 3.0 system file tables and FCB tables:
Offset    Size    Description
 00h    DWORD    pointer to next file table (offset FFFFh if last)
 04h    WORD    number of files in this table
 06h  38h bytes per file
    Offset    Size    Description
     00h-1Eh as for DOS 3.1+ (see below)
     1Fh    WORD    byte offset of directory entry within sector
     21h 11 BYTEs    filename in FCB format (no path/period, blank-padded)
     2Ch    DWORD    (SHARE.EXE) pointer to previous SFT sharing same file
     30h    WORD    (SHARE.EXE) network machine number which opened file
            (Windows Enhanced mode DOSMGR uses the virtual machine
            ID as the machine number; see INT 2F/AX=1683h)
     32h    WORD    PSP segment of file's owner (first three entries for
            AUX/CON/PRN contain segment of IO.SYS startup code)
     34h    WORD    (SHARE.EXE) offset in SHARE code seg of share record
     36h    WORD    ??? apparently always 0000h

Format of DOS 3.1-3.3x, DR-DOS 5.0-6.0 system file tables and FCB tables:
Offset    Size    Description
 00h    DWORD    pointer to next file table (offset FFFFh if last)
 04h    WORD    number of files in this table
 06h  35h bytes per file
    Offset    Size    Description
     00h    WORD    number of file handles referring to this file
     02h    WORD    file open mode (see AH=3Dh)
            bit 15 set if this file opened via FCB
     04h    BYTE    file attribute (see AX=4301h)
     05h    WORD    device info word (see AX=4400h)
            bit 15 set if remote file
            bit 14 set means do not set file date/time on closing
            bit 12 set means don't inherit on EXEC
            bits 5-0 drive number for disk files
     07h    DWORD    pointer to device driver header if character device
            else pointer to DOS Drive Parameter Block (see AH=32h)
     0Bh    WORD    starting cluster of file
     0Dh    WORD    file time in packed format (see AX=5700h)
            not used for character devices in DR-DOS
     0Fh    WORD    file date in packed format (see AX=5700h)
            not used for character devices in DR-DOS
     11h    DWORD    file size
    ---system file table---
     15h    DWORD    current offset in file (may be larger than size of
            file; INT 21/AH=42h does not check new position)
    ---FCB table---
     15h    WORD    counter for last I/O to FCB
     17h    WORD    counter for last open of FCB
            (these are separate to determine the times of the
            latest I/O and open)
    ---
     19h    WORD    relative cluster within file of last cluster accessed
     1Bh    WORD    absolute cluster number of last cluster accessed
            0000h if file never read or written???
     1Dh    WORD    number of sector containing directory entry
     1Fh    BYTE    number of dir entry within sector (byte offset/32)
     20h 11 BYTEs    filename in FCB format (no path/period, blank-padded)
     2Bh    DWORD    (SHARE.EXE) pointer to previous SFT sharing same file
     2Fh    WORD    (SHARE.EXE) network machine number which opened file
            (Windows Enhanced mode DOSMGR uses the virtual machine
            ID as the machine number; see INT 2F/AX=1683h)
     31h    WORD    PSP segment of file's owner (see AH=26h) (first three
            entries for AUX/CON/PRN contain segment of IO.SYS
            startup code)
     33h    WORD    offset within SHARE.EXE code segment of
            sharing record (see above)  0000h = none

Format of DOS 4.0-6.0 system file tables and FCB tables:
Offset    Size    Description
 00h    DWORD    pointer to next file table (offset FFFFh if last)
 04h    WORD    number of files in this table
 06h  3Bh bytes per file
    Offset    Size    Description
     00h    WORD    number of file handles referring to this file
            FFFFh if in use but not referenced
     02h    WORD    file open mode (see AH=3Dh)
            bit 15 set if this file opened via FCB
     04h    BYTE    file attribute (see AX=4301h)
     05h    WORD    device info word (see also AX=4400h)
            bit 15 set if remote file
            bit 14 set means do not set file date/time on closing
            bit 13 set if named pipe
            bit 12 set if no inherit
            bit 11 set if network spooler
            bit 7  set if device, clear if file (only if local)
            bits 6-0 as for AX=4400h
     07h    DWORD    pointer to device driver header if character device
            else pointer to DOS Drive Parameter Block (see AH=32h)
            or REDIR data
     0Bh    WORD    starting cluster of file (local files only)
     0Dh    WORD    file time in packed format (see AX=5700h)
     0Fh    WORD    file date in packed format (see AX=5700h)
     11h    DWORD    file size
     15h    DWORD    current offset in file (SFT)
            LRU counters (FCB table, two WORDs)
    ---local file---
     19h    WORD    relative cluster within file of last cluster accessed
     1Bh    DWORD    number of sector containing directory entry
     1Fh    BYTE    number of dir entry within sector (byte offset/32)
    ---network redirector---
     19h    DWORD    pointer to REDIRIFS record
     1Dh  3 BYTEs    ???
    ------
     20h 11 BYTEs    filename in FCB format (no path/period, blank-padded)
     2Bh    DWORD    (SHARE.EXE) pointer to previous SFT sharing same file
     2Fh    WORD    (SHARE.EXE) network machine number which opened file
            (Windows Enhanced mode DOSMGR uses the virtual machine
            ID as the machine number; see INT 2F/AX=1683h)
     31h    WORD    PSP segment of file's owner (see AH=26h) (first three
            entries for AUX/CON/PRN contain segment of IO.SYS
            startup code)
     33h    WORD    offset within SHARE.EXE code segment of
            sharing record (see above)  0000h = none
     35h    WORD    (local) absolute cluster number of last clustr accessed
            (redirector) ???
     37h    DWORD    pointer to IFS driver for file, 0000000h if native DOS
Note:    the OS/2 2.0 DOS Boot Session does not properly fill in the filename
      field due to incomplete support for SFTs; the OS/2 2.0 DOS Window
      does not appear to support SFTs at all

Format of current directory structure (CDS) (array, LASTDRIVE entries):
Offset    Size    Description
 00h 67 BYTEs    ASCIZ path in form X:\PATH (local) or \\MACH\PATH (network)
 43h    WORD    drive attributes (see also note below and AX=5F07h)
        bit 15: uses network redirector     \ invalid if 00, installable
        bit 14: physical drive         / file system if 11
        bit 13: JOIN'ed      \ path above is true path that would be
        bit 12: SUBST'ed  / needed if not under SUBST or JOIN
        bit  7: remote drive hidden from redirector's assign-list and
              exempt from network connection make/break commands;
              set for CD-ROM drives
 45h    DWORD    pointer to Drive Parameter Block for drive (see AH=32h)
---local drives---
 49h    WORD    starting cluster of current directory
        0000h = root, FFFFh = never accessed
 4Bh    WORD    ??? seems to be FFFFh always
 4Dh    WORD    ??? seems to be FFFFh always
---network drives---
 49h    DWORD    pointer to redirector or REDIRIFS record, or FFFFh:FFFFh
        (DOS 4 only) available for use by IFS driver
 4Dh    WORD    stored user data from INT 21/AX=5F03h
------
 4Fh    WORD    offset in current directory path of backslash corresponding to
          root directory for drive
        this value specifies how many characters to hide from the
          "CHDIR" and "GETDIR" calls; normally set to 2 to hide the
          drive letter and colon, SUBST, JOIN, and networks change it
          so that only the appropriate portion of the true path is
          visible to the user
---DOS 4+ ---
 51h    BYTE    (DOS 4 only, remote drives) device type
        04h network drive
 52h    DWORD    pointer to IFS driver (DOS 4) or redirector block (DOS 5+) for
        this drive, 00000000h if native DOS
 56h    WORD    available for use by IFS driver
Notes:    the path for invalid drives is normally set to X:\, but may be empty
      after JOIN x: /D in DR-DOS 5.0 or NET USE x: /D in older LAN versions
    normally, only one of bits 13&12 may be set together with bit 14, but
      DR-DOS 5.0 uses other combinations for bits 15-12: 0111 JOIN,
      0001 SUBST, 0101 ASSIGN (see below)

Format of DR-DOS 5.0-6.0 current directory structure entry (array):
Offset    Size    Description
 00h 67 BYTEs    ASCIZ pathname of actual root directory for this logical drive
 43h    WORD    drive attributes
        1000h SUBSTed drive
        3000h??? JOINed drive
        4000h physical drive
        5000h ASSIGNed drive
        7000h JOINed drive
        8000h network drive
 45h    BYTE    physical drive number (0=A:) if this logical drive is valid
 46h    BYTE    ??? apparently flags for JOIN and ASSIGN
 47h    WORD    cluster number of start of parent directory (0000h = root)
 49h    WORD    entry number of current directory in parent directory
 4Bh    WORD    cluster number of start of current directory
 4Dh    WORD    used for media change detection (details not available)
 4Fh    WORD    cluster number of SUBST/JOIN "root" directory
        0000h if physical root directory

Format of device driver header:
Offset    Size    Description
 00h    DWORD    pointer to next driver, offset=FFFFh if last driver
 04h    WORD    device attributes
        Character device:
           bit 15 set (indicates character device)
           bit 14 IOCTL supported (see AH=44h)
           bit 13 (DOS 3+) output until busy supported
           bit 12 reserved
           bit 11 (DOS 3+) OPEN/CLOSE/RemMedia calls supported
           bits 10-8 reserved
           bit 7  (DOS 5+) Generic IOCTL check call supported (cmd 19h)
                (see AX=4410h,AX=4411h)
           bit 6  (DOS 3.2+) Generic IOCTL call supported (command 13h)
                (see AX=440Ch,AX=440Dh)
           bit 5  reserved
           bit 4  device is special (use INT 29 "fast console output")
           bit 3  device is CLOCK$ (all reads/writes use transfer
                record described below)
           bit 2  device is NUL
           bit 1  device is standard output
           bit 0  device is standard input
        Block device:
           bit 15 clear (indicates block device)
           bit 14 IOCTL supported
           bit 13 non-IBM format
           bit 12 network device (device is remote)
           bit 11 (DOS 3+) OPEN/CLOSE/RemMedia calls supported
           bit 10 reserved
           bit 9  direct I/O not allowed???
              (set by DOS 3.3 DRIVER.SYS for "new" drives)
           bit 8  ??? set by DOS 3.3 DRIVER.SYS for "new" drives
           bit 7  (DOS 5+) Generic IOCTL check call supported (cmd 19h)
                (see AX=4410h,AX=4411h)
           bit 6  (DOS 3.2+) Generic IOCTL call supported (command 13h)
                implies support for commands 17h and 18h
                (see AX=440Ch,AX=440Dh,AX=440Eh,AX=440Fh)
           bits 5-2 reserved
           bit 1   driver supports 32-bit sector addressing (DOS 3.31+)
           bit 0   reserved
        Note: for European MS-DOS 4.0, bit 11 also indicates that bits
            8-6 contain a version code (000 = DOS 3.0,3.1;
            001 = DOS 3.2, 010 = European DOS 4.0)
 06h    WORD    device strategy entry point
        call with ES:BX -> request header (see INT 2F/AX=0802h)
 08h    WORD    device interrupt entry point
---character device---
 0Ah  8 BYTEs    blank-padded character device name
---block device---
 0Ah    BYTE    number of subunits (drives) supported by driver
 0Bh  7 BYTEs    unused
---
 12h    WORD    (CD-ROM driver) reserved, must be 0000h
        appears to be another device chain
 14h    BYTE    (CD-ROM driver) drive letter (must initially be 00h)
 15h    BYTE    (CD-ROM driver) number of units
 16h  6 BYTEs    (CD-ROM driver) signature 'MSCDnn' where 'nn' is version
            (currently '00')

Format of CLOCK$ transfer record:
Offset    Size    Description
 00h    WORD    number of days since 1-Jan-1980
 02h    BYTE    minutes
 03h    BYTE    hours
 04h    BYTE    hundredths of second
 05h    BYTE    seconds

Format of DOS 2.x disk buffer:
Offset    Size    Description
 00h    DWORD    pointer to next disk buffer, offset = FFFFh if last
        least-recently used buffer is first in chain
 04h    BYTE    drive (0=A, 1=B, etc), FFh if not in use
 05h  3 BYTEs    unused??? (seems always to be 00h 00h 01h)
 08h    WORD    logical sector number
 0Ah    BYTE    number of copies to write (1 for non-FAT sectors)
 0Bh    BYTE    sector offset between copies if multiple copies to be written
 0Ch    DWORD    pointer to DOS Drive Parameter Block (see AH=32h)
 10h        buffered data

Format of DOS 3.x disk buffer:
Offset    Size    Description
 00h    DWORD    pointer to next disk buffer, offset = FFFFh if last
        least-recently used buffer is first in chain
 04h    BYTE    drive (0=A,1=B, etc), FFh if not in use
 05h    BYTE    buffer flags
        bit 7: ???
        bit 6: buffer dirty
        bit 5: buffer has been referenced
        bit 4: ???
        bit 3: sector in data area
        bit 2: sector in a directory, either root or subdirectory
        bit 1: sector in FAT
        bit 0: boot sector??? (guess)
 06h    WORD    logical sector number
 08h    BYTE    number of copies to write (1 for non-FAT sectors)
 09h    BYTE    sector offset between copies if multiple copies to be written
 0Ah    DWORD    pointer to DOS Drive Parameter Block (see AH=32h)
 0Eh    WORD    unused??? (almost always 0)
 10h        buffered data

Format of DOS 4.00 (pre UR 25066) disk buffer info:
Offset    Size    Description
 00h    DWORD    pointer to array of disk buffer hash chain heads (see below)
 04h    WORD    number of disk buffer hash chains (referred to as NDBCH below)
 06h    DWORD    pointer to lookahead buffer, zero if not present
 0Ah    WORD    number of lookahead sectors, else zero (the y in BUFFERS=x,y)
 0Ch    BYTE    00h if buffers in EMS (/X), FFh if not
 0Dh    WORD    EMS handle for buffers, zero if not in EMS
 0Fh    WORD    EMS physical page number used for buffers (usually 255)
 11h    WORD    ??? seems always to be 0001h
 13h    WORD    segment of EMS physical page frame
 15h    WORD    ??? seems always to be zero
 17h  4 WORDs    EMS partial page mapping information???

Format of DOS 4.01 (from UR 25066 Corrctive Services Disk on) disk buffer info:
Offset    Size    Description
 00h    DWORD    pointer to array of disk buffer hash chain heads (see below)
 04h    WORD    number of disk buffer hash chains (referred to as NDBCH below)
 06h    DWORD    pointer to lookahead buffer, zero if not present
 0Ah    WORD    number of lookahead sectors, else zero (the y in BUFFERS=x,y)
 0Ch    BYTE    01h, possibly to distinguish from pre-UR 25066 format
 0Dh    WORD    ??? EMS segment for BUFFERS (only with /XD)
 0Fh    WORD    ??? EMS physical page number of EMS seg above (only with /XD)
 11h    WORD    ??? EMS segment for ??? (only with /XD)
 13h    WORD    ??? EMS physical page number of above (only with /XD)
 15h    BYTE    ??? number of EMS page frames present (only with /XD)
 16h    WORD    segment of one-sector workspace buffer allocated in main memory
          if BUFFERS/XS or /XD options in effect, possibly to avoid DMA
          into EMS
 18h    WORD    EMS handle for buffers, zero if not in EMS
 1Ah    WORD    EMS physical page number used for buffers (usually 255)
 1Ch    WORD    ??? appears always to be 0001h
 1Eh    WORD    segment of EMS physical page frame
 20h    WORD    ??? appears always to be zero
 22h    BYTE    00h if /XS, 01h if /XD, FFh if BUFFERS not in EMS

Format of DOS 4.x disk buffer hash chain head (array, one entry per chain):
Offset    Size    Description
 00h    WORD    EMS logical page number in which chain is resident, -1 if not
        in EMS
 02h    DWORD    pointer to least recently used buffer header.  All buffers on
        this chain are in the same segment.
 06h    BYTE    number of dirty buffers on this chain
 07h    BYTE    reserved (00h)
Notes:    buffered disk sectors are assigned to chain N where N is the sector's
      address modulo NDBCH,     0 <= N <= NDBCH-1
    each chain resides completely within one EMS page
    this structure is in main memory even if buffers are in EMS

Format of DOS 4.0-6.0 disk buffer:
Offset    Size    Description
 00h    WORD    forward ptr, offset only, to next least recently used buffer
 02h    WORD    backward ptr, offset only
 04h    BYTE    drive (0=A,1=B, etc) if bit 7 clear
        SFT index if bit 7 set
        FFh if not in use
 05h    BYTE    buffer flags
        bit 7: remote buffer
        bit 6: buffer dirty
        bit 5: buffer has been referenced (reserved in DOS 5+)
        bit 4: search data buffer (only valid if remote buffer)
        bit 3: sector in data area
        bit 2: sector in a directory, either root or subdirectory
        bit 1: sector in FAT
        bit 0: reserved
 06h    DWORD    logical sector number (local buffers only)
 0Ah    BYTE    number of copies to write
        for FAT sectors, same as number of FATs
        for data and directory sectors, usually 1
 0Bh    WORD    offset in sectors between copies to write for FAT sectors
 0Dh    DWORD    pointer to DOS Drive Parameter Block (see AH=32h)
 11h    WORD    size of data in buffer if remote buffer (see flags above)
 13h    BYTE    reserved (padding)
 14h        buffered data
Note:    for DOS 4.x, all buffered sectors which have the same hash value
      (computed as the sum of high and low words of the logical sector
      number divided by the number of disk buffer chains) are on the same
      doubly-linked circular chain; for DOS 5+, only a single circular
      chain exists.
    the links consist of offset addresses only, the segment being the same
      for all buffers in the chain.

Format of DOS 5.0-6.0 disk buffer info:
Offset    Size    Description
 00h    DWORD    pointer to least-recently-used buffer header (may be in HMA)
        (see above)
 04h    WORD    number of dirty disk buffers
 06h    DWORD    pointer to lookahead buffer, zero if not present
 0Ah    WORD    number of lookahead sectors, else zero (the y in BUFFERS=x,y)
 0Ch    BYTE    buffer location
        00h base memory, no workspace buffer
        01h HMA, workspace buffer in base memory
 0Dh    DWORD    pointer to one-segment workspace buffer in base memory
 11h  3 BYTEs    unused
 14h    WORD    ???
 16h    BYTE    flag: INT 24 fail while making an I/O status call
 17h    BYTE    temp storage for user memory allocation strategy during EXEC
 18h    BYTE    counter: number of INT 21 calls for which A20 is off
 19h    BYTE    bit flags
        bit 0: ???
        bit 1: SWITCHES=/W specified in CONFIG.SYS (don't load
            WINA20.SYS when MS Windows 3.0 starts)
        bit 2: in EXEC state (INT 21/AX=4B05h)
 1Ah    WORD    offset of unpack code start (used only during INT 21/AX=4B05h)
 1Ch    BYTE    bit 0 set iff UMB MCB chain linked to normal MCB chain
 1Dh    WORD    minimum paragraphs of memory required by program being EXECed
 1Fh    WORD    segment of first MCB in upper memory blocks or FFFFh if DOS
        memory chain in base 640K only (first UMB MCB usually at 9FFFh,
        locking out video memory with a DOS-owned memory block)
 21h    WORD    paragraph from which to start scanning during memory allocation

Format of IFS driver list:
Offset    Size    Description
 00h    DWORD    pointer to next driver header
 04h  8 BYTEs    IFS driver name (blank padded), as used by FILESYS command
 0Ch  4 BYTEs    ???
 10h    DWORD    pointer to IFS utility function entry point (see below)
        call with ES:BX -> IFS request (see below)
 14h    WORD    offset in header's segment of driver entry point
    ???

Call IFS utility function entry point with:
    AH = 20h miscellaneous functions
        AL = 00h get date
        Return: CX = year
            DH = month
            DL = day
        AL = 01h get process ID and computer ID
        Return: BX = current PSP segment
            DX = active network machine number
        AL = 05h get file system info
        ES:DI -> 16-byte info buffer
        Return: buffer filled
            Offset    Size    Description
             00h  2 BYTEs    unused
             02h    WORD    number of SFTs (actually counts only
                    the first two file table arrays)
             04h    WORD    number of FCB table entries
             06h    WORD    number of proctected FCBs
             08h  6 BYTEs    unused
             0Eh    WORD    largest sector size supported
        AL = 06h get machine name
        ES:DI -> 18-byte buffer for name
        Return: buffer filled with name starting at offset 02h
        AL = 08h get sharing retry count
        Return: BX = sharing retry count
        AL = other
        Return: CF set
    AH = 21h get redirection state
        BH = type (03h disk, 04h printer)
        Return: BH = state (00h off, 01h on)
    AH = 22h ??? some sort of time calculation
        AL = 00h ???
            nonzero ???
    AH = 23h ??? some sort of time calculation
    AH = 24h compare filenames
        DS:SI -> first ASCIZ filename
        ES:DI -> second ASCIZ filename
        Return: ZF set if files are same ignoring case and / vs \
    AH = 25h normalize filename
        DS:SI -> ASCIZ filename
        ES:DI -> buffer for result
        Return: filename uppercased, forward slashes changed to backslashes
    AH = 26h get DOS stack
        Return: DS:SI -> top of stack
            CX = size of stack in bytes
    AH = 27h increment InDOS flag
    AH = 28h decrement InDOS flag
Note:    IFS drivers which do not wish to implement functions 20h or 24h-28h may
      pass them on to the default handler pointed at by [LoL+37h]

Format of IFS request block:
Offset    Size    Description
 00h    WORD    total size in bytes of request
 02h    BYTE    class of request
        02h ???
        03h redirection
        04h ???
        05h file access
        06h convert error code to string
        07h ???
 03h    WORD    returned DOS error code
 05h    BYTE    IFS driver exit status
        00h success
        01h ???
        02h ???
        03h ???
        04h ???
        FFh internal failure
 06h 16 BYTEs    ???
---request class 02h---
 16h    BYTE    function code
        04h ???
 17h    BYTE    unused???
 18h    DWORD    pointer to ???
 1Ch    DWORD    pointer to ???
 20h  2 BYTEs    ???
---request class 03h---
 16h    BYTE    function code
 17h    BYTE    ???
 18h    DWORD    pointer to ???
 1Ch    DWORD    pointer to ???
 22h    WORD    returned ???
 24h    WORD    returned ???
 26h    WORD    returned ???
 28h    BYTE    returned ???
 29h    BYTE    unused???
---request class 04h---
 16h    DWORD    pointer to ???
 1Ah    DWORD    pointer to ???
---request class 05h---
 16h    BYTE    function code
        01h flush disk buffers
        02h get disk space
        03h MKDIR
        04h RMDIR
        05h CHDIR
        06h delete file
        07h rename file
        08h search directory
        09h file open/create
        0Ah LSEEK
        0Bh read from file
        0Ch write to file
        0Dh lock region of file
        0Eh commit/close file
        0Fh get/set file attributes
        10h printer control
        11h ???
        12h process termination
        13h ???
    ---class 05h function 01h---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h  4 BYTEs    ???
     26h    BYTE    ???
     27h    BYTE    ???
    ---class 05h function 02h---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h  4 BYTEs    ???
     26h    WORD    returned total clusters
     28h    WORD    returned sectors per cluster
     2Ah    WORD    returned bytes per sector
     2Ch    WORD    returned available clusters
     2Eh    BYTE    returned ???
     2Fh    BYTE    ???
    ---class 05h functions 03h,04h,05h---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h  4 BYTEs    ???
     26h    DWORD    pointer to directory name
    ---class 05h function 06h---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h  4 BYTEs    ???
     26h    WORD    attribute mask
     28h    DWORD    pointer to filename
    ---class 05h function 07h---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h  4 BYTEs    ???
     26h    WORD    attribute mask
     28h    DWORD    pointer to source filespec
     2Ch    DWORD    pointer to destination filespec
    ---class 05h function 08h---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h  4 BYTEs    ???
     26h    BYTE    00h FINDFIRST
            01h FINDNEXT
     28h    DWORD    pointer to FindFirst search data + 01h if FINDNEXT
     2Ch    WORD    search attribute if FINDFIRST
     2Eh    DWORD    pointer to filespec if FINDFIRST
    ---class 05h function 09h---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h    DWORD    pointer to IFS open file structure (see below)
     26h    WORD    ???  \ together, specify open vs. create, whether or
     28h    WORD    ???  / not to truncate
     2Ah  4 BYTEs    ???
     2Eh    DWORD    pointer to filename
     32h  4 BYTEs    ???
     36h    WORD    file attributes on call
            returned ???
     38h    WORD    returned ???
    ---class 05h function 0Ah---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h    DWORD    pointer to IFS open file structure (see below)
     26h    BYTE    seek type (02h = from end)
     28h    DWORD    offset on call
            returned new absolute position
    ---class 05h functions 0Bh,0Ch---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h    DWORD    pointer to IFS open file structure (see below)
     28h    WORD    number of bytes to transfer
            returned bytes actually transferred
     2Ah    DWORD    transfer address
    ---class 05h function 0Dh---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h    DWORD    pointer to IFS open file structure (see below)
     26h    BYTE    file handle???
     27h    BYTE    unused???
     28h    WORD    ???
     2Ah    WORD    ???
     2Ch    WORD    ???
     2Eh    WORD    ???
    ---class 05h function 0Eh---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h    DWORD    pointer to IFS open file structure (see below)
     26h    BYTE    00h commit file
            01h close file
     27h    BYTE    unused???
    ---class 05h function 0Fh---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h  4 BYTEs    ???
     26h    BYTE    02h GET attributes
            03h PUT attributes
     27h    BYTE    unused???
     28h 12 BYTEs    ???
     34h    WORD    search attributes???
     36h    DWORD    pointer to filename
     3Ah    WORD    (GET) returned ???
     3Ch    WORD    (GET) returned ???
     3Eh    WORD    (GET) returned ???
     40h    WORD    (GET) returned ???
     42h    WORD    (PUT) new attributes
            (GET) returned attributes
    ---class 05h function 10h---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h    DWORD    pointer to IFS open file structure (see below)
     26h    WORD    ???
     28h    DWORD    pointer to ???
     2Ch    WORD    ???
     2Eh    BYTE    ???
     2Fh    BYTE    subfunction
            01h get printer setup
            03h ???
            04h ???
            05h ???
            06h ???
            07h ???
            21h set printer setup
    ---class 05h function 11h---
     17h  7 BYTEs    ???
     1Eh    DWORD    pointer to ???
     22h    DWORD    pointer to IFS open file structure (see below)
     26h    BYTE    subfunction
     27h    BYTE    unused???
     28h    WORD    ???
     2Ah    WORD    ???
     2Ch    WORD    ???
     2Eh    BYTE    ???
     2Fh    BYTE    ???
    ---class 05h function 12h---
     17h 15 BYTEs    unused???
     26h    WORD    PSP segment
     28h    BYTE    type of process termination
     29h    BYTE    unused???
    ---class 05h function 13h---
     17h 15 BYTEs    unused???
     26h    WORD    PSP segment
---request class 06h---
 16h    DWORD    returned pointer to string corresponding to error code at 03h
 1Ah    BYTE    returned ???
 1Bh    BYTE    unused
---request class 07h---
 16h    DWORD    pointer to IFS open file structure (see below)
 1Ah    BYTE    ???
 1Bh    BYTE    unused???

Format of IFS open file structure:
Offset    Size    Description
 00h    WORD    ???
 02h    WORD    device info word
 04h    WORD    file open mode
 06h    WORD    ???
 08h    WORD    file attributes
 0Ah    WORD    owner's network machine number
 0Ch    WORD    owner's PSP segment
 0Eh    DWORD    file size
 12h    DWORD    current offset in file
 16h    WORD    file time
 18h    WORD    file date
 1Ah 11 BYTEs    filename in FCB format
 25h    WORD    ???
 27h    WORD    hash value of SFT address
        (low word of linear address + segment&F000h)
 29h  3 WORDs    network info from SFT
 2Fh    WORD    ???

Format of one item in DOS 4+ list of special program names:
Offset    Size    Description
 00h    BYTE    length of name (00h = end of list)
 01h  N BYTEs    name in format name.ext
 N    2 BYTEs    DOS version to return for program (major,minor)
        (see AH=30h,INT 2F/AX=122Fh)
---DOS 4 only---
 N+2    BYTE    number of times to return fake version number (FFh = always)
Note:    if the name of the executable for the program making the DOS "get
      version" call matches one of the names in this list, DOS returns the
      specified version rather than the true version number
--------v-215252-----------------------------
INT 21 - VIRUS - "516"/"Leapfrog" - INSTALLATION CHECK
    AX = 5252h
Return: BX = FFEEh if resident
SeeAlso: AX=4BFFh"Cascade",AX=58CCh
--------D-2153-------------------------------
INT 21 - DOS 2+ internal - TRANSLATE BIOS PARAMETER BLOCK TO DRIVE PARAM BLOCK
    AH = 53h
    DS:SI -> BIOS Parameter Block (see below)
    ES:BP -> buffer for Drive Parameter Block (see AH=32h for format)
Return: ES:BP buffer filled
Note:    for DOS 3+, the cluster at which to start searching is set to 0000h
      and the number of free clusters is set to FFFFh (unknown)

Format of BIOS Parameter Block:
Offset    Size    Description
 00h    WORD    number of bytes per sector
 02h    BYTE    number of sectors per cluster
 03h    WORD    number of reserved sectors at start of disk
 05h    BYTE    number of FATs
 06h    WORD    number of entries in root directory
 08h    WORD    total number of sectors
        for DOS 4+, set to zero if partition >32M, then set DWORD at
          15h to actual number of sectors
 0Ah    BYTE    media ID byte
 0Bh    WORD    number of sectors per FAT
---DOS 3+---
 0Dh    WORD    number of sectors per track
 0Fh    WORD    number of heads
 11h    DWORD    number of hidden sectors
 15h 11 BYTEs    reserved
---DOS 4+ ---
 15h    DWORD    total number of sectors if word at 08h contains zero
 19h  6 BYTEs    ???
 1Fh    WORD    number of cylinders
 21h    BYTE    device type
 22h    WORD    device attributes (removable or not, etc)
---DR-DOS 5+ ---
 15h    DWORD    total number of sectors if word at 08h contains zero
 19h  6 BYTEs    reserved
---European MS-DOS 4.00---
 15h    DWORD    total number of sectors if word at 08h contains zero
        (however, this DOS does not actually implement >32M partitions)
--------D-2154-------------------------------
INT 21 - DOS 2+ - GET VERIFY FLAG
    AH = 54h
Return: AL = verify flag
        00h off
        01h on (all disk writes verified after writing)
SeeAlso: AH=2Eh
--------D-2155-------------------------------
INT 21 - DOS 2+ internal - CREATE CHILD PSP
    AH = 55h
    DX = segment at which to create new PSP
    SI = (DOS 3+) value to place in memory size field at DX:[0002h]
Return: CF clear if successful

Notes:    creates a "child" PSP rather than making an exact copy of the current
      PSP; the new PSP's parent pointer is set to the current PSP and the
      reference count for each inherited file is incremented
    (DOS 2+) sets current PSP to DX
    (DOS 3+) marks "no inherit" file handles as closed in child PSP
SeeAlso: AH=26h,AH=50h
--------D-2156-------------------------------
INT 21 - DOS 2+ - "RENAME" - RENAME FILE
    AH = 56h
    DS:DX -> ASCIZ filename of existing file (no wildcards, but see below)
    ES:DI -> ASCIZ new filename (no wildcards)
    CL = attribute mask (server call only, see below)
Return: CF clear if successful
    CF set on error
        AX = error code (02h,03h,05h,11h) (see AH=59h)
Notes:    allows move between directories on same logical volume
    does not set the archive attribute (see AX=4300h), which results in
      incremental backups not backing up the file under its new name
    open files should not be renamed
    (DOS 3+) allows renaming of directories
    (DOS 3.1+) wildcards are allowed if invoked via AX=5D00h, in which case
      error 12h (no more files) is returned on success, and both source and
      destination specs must be canonical (as returned by AH=60h).
      Wildcards in the destination are replaced by the corresponding char
      of each source file being renamed.  Under DOS 3.x, the call will fail
      if the destination wildcard is *.* or equivalent; under DR-DOS 5.0,
      the call will fail if any wildcards are used.     When invoked via
      AX=5D00h, only those files matching the attribute mask in CL are
      renamed.
    under the FlashTek X-32 DOS extender, the old-name pointer is in DS:EDX
      and the new-name pointer is in ES:EDI (DS must equal ES)
BUG:    under DR-DOS 3.41, this function will generate a new directory entry
      with the new name (including any wildcards) which can only be removed
      with a sector editor when invoked via AX=5D00h
SeeAlso: AH=17h,AX=4301h,AH=60h,AX=5D00h
--------D-215700-----------------------------
INT 21 - DOS 2+ - GET FILE'S DATE AND TIME
    AX = 5700h
    BX = file handle
Return: CF clear if successful
        CX = file's time
        bits 15-11: hours (0-23)
             10-5:  minutes
              4-0:  seconds/2
        DX = file's date
        bits 15-9: year - 1980
              8-5: month
              4-0: day
    CF set on error
        AX = error code (01h,06h) (see AH=59h)
Note:    under DR-DOS 3.41 and 5.0, this function returns 0 (no date/time) for
      character devices; MS-DOS returns date and time of opening
SeeAlso: AX=5701h
--------D-215701-----------------------------
INT 21 - DOS 2+ - SET FILE'S DATE AND TIME
    AX = 5701h
    BX = file handle
    CX = new time (see AX=5700h)
    DX = new date (see AX=5700h)
Return: CF clear if successful
    CF set on error
        AX = error code (01h,06h) (see AH=59h)
SeeAlso: AX=5700h
--------D-215702-----------------------------
INT 21 - DOS 4.x only - GET EXTENDED ATTRIBUTES FOR FILE
    AX = 5702h
    BX = file handle
    CX = size of result buffer or 0000h
    DS:SI -> EAP list (see below)
    ES:DI -> buffer for returned EAV list (see below)
Return: CF clear if successful
        CX = size of returned data
    CF set on error
        AX = error code (see AH=59h)
Desc:    get the current value of one or more extended attributes
Notes:    if CX=0000h on entry, ES:DI is ignored and no data is actually
      returned, only the amount of data which is available
    the default DOS 4 behavior is to return a single word of 0000h (no
      structures) in the result buffer if CX>=0002h on entry
SeeAlso: AX=5703h,AX=5704h,AH=6Eh,INT 2F/AX=112Dh

Format of EAP (extended attribute properties) list:
Offset    Size    Description
 00h    WORD    number of EAP structures following
 02h    var    array of EAP structures (see below)

Format of EAP (extended attribute property) structure:
Offset    Size    Description
 00h    BYTE    attribute type
        01h boolean (either 00h or 01h)
        02h number (BYTE, WORD, or DWORD)
        03h string
        04h date stamp
        05h time stamp
 01h    WORD    EAP flags (see below)
 03h    BYTE    size of reference string (name)
 04h  N BYTEs    reference string

Bitfields for EAP flags:
 bit 12 unchangeable
 bit 13 ignore
 bit 14 unchangeable
 bit 15 used by COMMAND.COM for code page, but not understood by ATTRIB

Format of EAV (extended attribute value) list:
Offset    Size    Description
 00h    WORD    number of EAV structures following
 02h    var    array of Extended Attribute Value structures

Format of Extended Attribute Value structures:
Offset    Size    Description
 00h  4 BYTEs    ???
 04h    BYTE    size of reference string
 05h    WORD    size of value
 07h    var    reference string
    var    value
----------215702-----------------------------
INT 21 - OS/2 v1.1+ Family API - DosQFileInfo
    AX = 5702h
    BX = file handle
    CX = size of buffer for information
    DX = level of information
    ES:DI -> buffer for information
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5702h/BX=FFFFh,AX=5703h"OS/2"
----------215702BXFFFF-----------------------
INT 21 - OS/2 v1.1+ Compatibility Box Family API - DosQPathInfo
    AX = 5702h
    BX = FFFFh
    CX = size of buffer for information
    DX = level of information (0002h)
    DS:SI -> filename
    ES:DI -> buffer for information (see below)
Return: CF clear if successful
        AL = 00h
    CF set on error
        AX = error code
SeeAlso: AX=5702h"OS/2",AX=5703h/BX=FFFFh

Format of path information:
Offset    Size    Description
 00h 22 BYTEs    ???
 16h    DWORD    extended attribute size (none present if less than 5)
--------D-215703-----------------------------
INT 21 - DOS 4.x only - GET EXTENDED ATTRIBUTE PROPERTIES
    AX = 5703h
    BX = file handle
    CX = size of result buffer or 0000h
    ES:DI -> result buffer
Return: CF clear if successful
        CX = size of returned data
    CF set on error
        AX = error code (see AH=59h)
    ES:DI -> zero word (DOS 4.0) if CX >= 2 on entry
Desc:    get a list of the extended attributes which are defined for the
      specified file
Notes:    if CX=0000h on entry, ES:DI is ignored and no data is actually
      returned, only the amount of data which is available
    the default DOS 4 behavior is to return a trivial EAP list consisting
      of the single word 0000h (no EAP structures) if CX>=0002h on entry
SeeAlso: AX=5702h,AX=5704h,AH=6Eh,INT 2F/AX=112Dh
----------215703-----------------------------
INT 21 - OS/2 v1.1+ Family API - DosSetFileInfo
    AX = 5703h
    BX = file handle
    CX = size of information buffer
    DX = level of information
    ES:DI -> information buffer
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5702h"OS/2",AX=5703h/BX=FFFFh
----------215703BXFFFF-----------------------
INT 21 - OS/2 v1.1+ Family API - DosSetPathInfo
    AX = 5703h
    BX = FFFFh
    CX = size of information buffer
    DX = level of information
    DS:SI -> filename
    ES:DI -> information buffer
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5702h/BX=FFFFh,AX=5703h"OS/2"
--------D-215704-----------------------------
INT 21 - DOS 4.x only - SET EXTENDED ATTRIBUTES
    AX = 5704h
    BX = file handle
    ES:DI -> EAV list (see AX=5702h)
Return: CF clear if successful
    CF set on error
        AX = error code (see AH=59h)
Note:    the default DOS 4 behavior is to do nothing and return successfully
SeeAlso: AX=5702h,AX=5703h,INT 2F/AX=112Dh
----------215757BX5757-----------------------
INT 21 U - IBM Genie - Resident Manager - INSTALLATION CHECK
    AX = 5757h
    BX = 5757h
Return: AX = 0000h if installed
        BX = ???
        DX = ???
        DS:SI -> list of 27 DWORD entry point addresses
Program: IBM Genie is a set of utility TSRs by Helix Software
Note:    other functions possible if BX <> 5757h, but details not yet available
----------215758-----------------------------
INT 21 U - Headroom - API
    AX = 5758h
    BL = function
        00h ???
        01h get Headroom location
        Return: CF clear if installed
                AX = PSP segment of Headroom TSR
                BX = paragraphs of memory used by Headroom
            CF set if not (normal DOS return)
        Note:    this function is also used as an installation check
        02h get INT 21 handler
        Return: CF clear
            ES:BX -> Headroom's INT 21 handler
        Note: also sets unknown flag
        03h launch application???
        DS:SI -> 233-byte application record
        Return: ???
        04h ???
        ???
        Return: CF clear
        05h get swap directory
        Return: CF clear
            DX:AX -> ASCIZ swap directory name
        06h ???
        DX = ???
        Return: CF clear
        07h ???
        08h ???
        09h get current application
        Return: BX = application number
        0Ah ???
        DX = application number
        DS:SI = ???
        Return: ???
        0Bh ???
        0Ch ???
        DX = application number
        ???
        Return: ???
        0Dh ???
        DX = application number
        ???
        Return: ???
        0Eh get ???
        Return: CF clear
            AX = ???
        0Fh set ??? flag
        10h clear ??? flag
        11h find application by name
        DS:SI -> ASCIZ application name
        Return: CF clear
            AX = application number or FFFFh if not loaded
        12h ???
        DX = application number
        Return: CF clear
            ???
        13h ???
        Return: CF clear
        14h ???
        same as function 13h
        15h set ???
        DX = ???
        16h get ???
        Return: AX = ??? set by function 15h
        17h get ???
        Return: BX = ???
            CX = ??? (may be pointer in BX:CX)
        18h BUG: branches incorrectly due to fencepost error
Program: Headroom is a TSR/task switcher by Helix Software
SeeAlso: AX=4C57h,AX=5757h
--------D-2158-------------------------------
INT 21 - DOS 3+ - GET OR SET MEMORY ALLOCATION STRATEGY
    AH = 58h
    AL = subfunction
        00h get allocation strategy
        Return: AX = current strategy
                00h low memory first fit
                01h low memory best fit
                02h low memory last fit
             ---DOS 5+ ---
                40h high memory first fit
                41h high memory best fit
                42h high memory last fit
                80h first fit, try high then low memory
                81h best fit, try high then low memory
                82h last fit, try high then low memory
        01h set allocation strategy
        BL = new allocation strategy (see above)
        BH = 00h (DOS 5+)
Return: CF clear if successful
    CF set on error
        AX = error code (01h) (see AH=59h)
Notes:    the Set subfunction accepts any value in BL for DOS 3.x and 4.x;
      2 or greater means last fit
    the Get subfunction returns the last value set
    setting an allocation strategy involving high memory does not
      automatically link in the UMB memory chain; this must be done
      explicitly with AX=5803h in order to actually allocate high memory
    a program which changes the allocation strategy should restore it
      before terminating
    Toshiba MS-DOS 2.11 supports subfunctions 00h and 01h
    DR-DOS 3.41 reportedly reverses subfunctions 00h and 01h
SeeAlso: AH=48h,AH=49h,AH=4Ah,INT 2F/AX=4310h,INT 67/AH=3Fh
--------D-2158-------------------------------
INT 21 - DOS 5+ - GET OR SET UMB LINK STATE
    AH = 58h
    AL = subfunction
        02h get UMB link state
        Return: AL = 00h UMBs not part of DOS memory chain
               = 01h UMBs in DOS memory chain
        03h set UMB link state
        BX = 0000h remove UMBs from DOS memory chain
           = 0001h add UMBs to DOS memory chain
Return: CF clear if successful
    CF set on error
        AX = error code (01h) (see AH=59h)
Note:    a program which changes the UMB link state should restore it before
      terminating
--------v-2158CC-----------------------------
INT 21 - VIRUS - "1067"/"Headcrash" - INSTALLATION CHECK
    AX = 58CCh
Return: CF clear if resident
SeeAlso: AX=5252h,AX=58DDh,AX=6969h
--------v-2158DD-----------------------------
INT 21 - VIRUS - "1067"/"Headcrash" - GET ORIGINAL INT 21h VECTOR
    AX = 58DDh
Return: CX = code segment of virus
    ES:BX = old INT 21h vector
SeeAlso: AX=5252h,AX=58CCh,AX=6969h
--------D-2159--BX0000-----------------------
INT 21 - DOS 3+ - GET EXTENDED ERROR INFORMATION
    AH = 59h
    BX = 0000h
Return: AX = extended error code (see below)
    BH = error class (see below)
    BL = recommended action (see below)
    CH = error locus (see below)
    ES:DI may be pointer (see error code list below)
    CL, DX, SI, BP, and DS destroyed
Notes:    functions available under DOS 2.x map the true DOS 3+ error code into
      one supported under DOS 2.x
    you should call this function to retrieve the true error code when an
      FCB or DOS 2.x call returns an error
    under DR-DOS 5.0, this function does not use any of the DOS-internal
      stacks and may thus be called at any time
SeeAlso: AH=59h/BX=0001h,AX=5D0Ah,INT 2F/AX=122Dh

Values for extended error code:
 00h (0)   no error
 01h (1)   function number invalid
 02h (2)   file not found
 03h (3)   path not found
 04h (4)   too many open files (no handles available)
 05h (5)   access denied
 06h (6)   invalid handle
 07h (7)   memory control block destroyed
 08h (8)   insufficient memory
 09h (9)   memory block address invalid
 0Ah (10)  environment invalid (usually >32K in length)
 0Bh (11)  format invalid
 0Ch (12)  access code invalid
 0Dh (13)  data invalid
 0Eh (14)  reserved
 0Fh (15)  invalid drive
 10h (16)  attempted to remove current directory
 11h (17)  not same device
 12h (18)  no more files
---DOS 3+---
 13h (19)  disk write-protected
 14h (20)  unknown unit
 15h (21)  drive not ready
 16h (22)  unknown command
 17h (23)  data error (CRC)
 18h (24)  bad request structure length
 19h (25)  seek error
 1Ah (26)  unknown media type (non-DOS disk)
 1Bh (27)  sector not found
 1Ch (28)  printer out of paper
 1Dh (29)  write fault
 1Eh (30)  read fault
 1Fh (31)  general failure
 20h (32)  sharing violation
 21h (33)  lock violation
 22h (34)  disk change invalid
    ES:DI -> ASCIZ volume label of required disk
 23h (35)  FCB unavailable
 24h (36)  sharing buffer overflow
 25h (37)  (DOS 4+) code page mismatch
 26h (38)  (DOS 4+) cannot complete file operation (out of input)
 27h (39)  (DOS 4+) insufficient disk space
 28h-31h   reserved
 32h (50)  network request not supported
 33h (51)  remote computer not listening
 34h (52)  duplicate name on network
 35h (53)  network name not found
 36h (54)  network busy
 37h (55)  network device no longer exists
 38h (56)  network BIOS command limit exceeded
 39h (57)  network adapter hardware error
 3Ah (58)  incorrect response from network
 3Bh (59)  unexpected network error
 3Ch (60)  incompatible remote adapter
 3Dh (61)  print queue full
 3Eh (62)  queue not full
 3Fh (63)  not enough space to print file
 40h (64)  network name was deleted
 41h (65)  network: Access denied
 42h (66)  network device type incorrect
 43h (67)  network name not found
 44h (68)  network name limit exceeded
 45h (69)  network BIOS session limit exceeded
 46h (70)  temporarily paused
 47h (71)  network request not accepted
 48h (72)  network print/disk redirection paused
 49h (73)  network software not installed
       (LANtastic) invalid network version
 4Ah (74)  unexpected adapter close
       (LANtastic) account expired
 4Bh (75)  (LANtastic) password expired
 4Ch (76)  (LANtastic) login attempt invalid at this time
 4Dh (77)  (LANtastic v3+) disk limit exceeded on network node
 4Eh (78)  (LANtastic v3+) not logged in to network node
 4Fh (79)  reserved
 50h (80)  file exists
 51h (81)  reserved
 52h (82)  cannot make directory
 53h (83)  fail on INT 24h
 54h (84)  (DOS 3.3+) too many redirections
 55h (85)  (DOS 3.3+) duplicate redirection
 56h (86)  (DOS 3.3+) invalid password
 57h (87)  (DOS 3.3+) invalid parameter
 58h (88)  (DOS 3.3+) network write fault
 59h (89)  (DOS 4+) function not supported on network
 5Ah (90)  (DOS 4+) required system component not installed
 64h (100) (MSCDEX) unknown error
 65h (101) (MSCDEX) not ready
 66h (102) (MSCDEX) EMS memory no longer valid
 67h (103) (MSCDEX) not High Sierra or ISO-9660 format
 68h (104) (MSCDEX) door open

Values for Error Class:
 01h    out of resource (storage space or I/O channels)
 02h    temporary situation (file or record lock)
 03h    authorization (denied access)
 04h    internal (system software bug)
 05h    hardware failure
 06h    system failure (configuration file missing or incorrect)
 07h    application program error
 08h    not found
 09h    bad format
 0Ah    locked
 0Bh    media error
 0Ch    already exists
 0Dh    unknown

Values for Suggested Action:
 01h    retry
 02h    delayed retry
 03h    prompt user to reenter input
 04h    abort after cleanup
 05h    immediate abort
 06h    ignore
 07h    retry after user intervention

Values for Error Locus:
 01h    unknown or not appropriate
 02h    block device (disk error)
 03h    network related
 04h    serial device (timeout)
 05h    memory related
--------D-2159--BX0001-----------------------
INT 21 - European MS-DOS 4.0 - GET HARD ERROR INFORMATION
    AH = 59h
    BX = 0001h
Return: ES:DI -> hard error information packet (see below) for most recent
        hard (critical) error
SeeAlso: AH=59h/BX=0000h,AH=95h,INT 24

Format of hard error information packet:
Offset    Size    Description
 00h    WORD    contents of AX at system entry
 02h    WORD    Process ID which encountered error
 04h    WORD    contents of AX at time of error
 06h    BYTE    error type
        00h physical I/O error
        01h disk change request
        02h file sharing violation
        03h FCB problem
        04h file locking violation
        05h bad FAT
        06h network detected error
 07h    BYTE    INT 24 error code
 08h    WORD    extended error code (see AH=59h/BX=0000h)
 0Ah    DWORD    pointer to associated device
--------D-215A-------------------------------
INT 21 - DOS 3+ - CREATE TEMPORARY FILE
    AH = 5Ah
    CX = file attribute (see AX=4301h)
    DS:DX -> ASCIZ path ending with a '\' + 13 zero bytes to receive the
        generated filename
Return: CF clear if successful
        AX = file handle opened for read/write in compatibility mode
        DS:DX pathname extended with generated name for temporary file
    CF set on error
        AX = error code (03h,04h,05h) (see AH=59h)
Desc:    creates a file with a unique name which must be explicitly deleted
BUGS:    COMPAQ DOS 3.31 hangs if the pathname is at XXXXh:0000h; it apparently
      wraps around to the end of the segment
    MS-DOS 5.00 revisions A and B and PC-DOS 5.00 revision A reportedly
      hang the system if the specified path is the root directory and the
      root directory is full (no free directory entries)
Note:    under the FlashTek X-32 DOS extender, the path pointer is in DS:EDX
SeeAlso: AH=3Ch,AH=5Bh
--------D-215B-------------------------------
INT 21 - DOS 3+ - CREATE NEW FILE
    AH = 5Bh
    CX = file attribute (see AX=4301h)
    DS:DX -> ASCIZ filename
Return: CF clear if successful
        AX = file handle opened for read/write in compatibility mode
    CF set on error
        AX = error code (03h,04h,05h,50h) (see AH=59h)
Notes:    unlike AH=3Ch, this function will fail if the specified file exists
      rather than truncating it; this permits its use in creating semaphore
      files because it is an atomic "test and set" operation
    under the FlashTek X-32 DOS extender, the filename pointer is in DS:EDX
SeeAlso: AH=3Ch,AH=5Ah
--------D-215C-------------------------------
INT 21 - DOS 3+ - "FLOCK" - RECORD LOCKING
    AH = 5Ch
    AL = subfunction
        00h lock region of file
        01h unlock region of file
    BX = file handle
    CX:DX = start offset of region within file
    SI:DI = length of region in bytes
Return: CF clear if successful
    CF set on error
        AX = error code (01h,06h,21h,24h) (see AH=59h)
Notes:    error returned unless SHARE or network installed
    an unlock call must specify the same region as some prior lock call
    locked regions become entirely inaccessible to other processes
    duplicate handles created with AH=45h or AH=46h inherit locks, but
      handles inherited by child processes (see AH=4Bh) do not
    under DR-DOS 3.41 and 5.0, if a process opens a file without the no-
      inherit flag and then starts a child, any locks set by the parent
      are ignored, and the child will only get an error if it tries to
      lock an area previously locked by the parent process
SeeAlso: AX=440Bh,AH=BCh,AH=BEh,INT 2F/AX=110Ah,INT 2F/AX=110Bh
--------D-215D00-----------------------------
INT 21 U - DOS 3.1+ internal - SERVER FUNCTION CALL
    AX = 5D00h
    DS:DX -> DOS parameter list (see below)
    DPL contains all register values for a call to INT 21h
Return: as appropriate for function being called
Notes:    does not check AH.  Out of range values will crash the system
    executes using specified computer ID and process ID
    sharing delay loops skipped
    a special sharing mode is enabled to handle FCBs opened across network
    wildcards are enabled for DELETE (AH=41h) and RENAME (AH=56h) under
      MS-DOS; under DR-DOS 3.41, wildcards corrupt the filesystem; and
      under DR-DOS 5.0-6.0, the call returns error code 03h due to improper
      support for the server function call (see below)
    an extra file attribute parameter is enabled for OPEN (AH=3Dh),
      DELETE (AH=41h), and RENAME (AH=56h)
    functions which take filenames require canonical names (as returned
      by AH=60h); this is apparently to prevent multi-hop file forwarding
BUGS:    the OS/2 2.0 DOS Boot Session incorrectly maps DOS drive letters,
      seemingly ignoring HPFS drives
    DR-DOS 5.0-6.0 merely recursively call INT 21 after loading the
      registers from the DPL, leading to problems for peer-to-peer
      networks
SeeAlso: AH=3Dh,AH=41h,AH=56h,AH=60h

Format of DOS parameter list:
Offset    Size    Description
 00h    WORD    AX
 02h    WORD    BX
 04h    WORD    CX
 06h    WORD    DX
 08h    WORD    SI
 0Ah    WORD    DI
 0Ch    WORD    DS
 0Eh    WORD    ES
 10h    WORD    reserved (0)
 12h    WORD    computer ID (0 = current system)
 14h    WORD    process ID (PSP segment on specified computer)
Note:    under Windows Enhanced mode, the computer ID is normally the virtual
      machine ID (see INT 2F/AX=1683h), though this can reportedly be
      changed by setting UniqueDOSPSP= in SYSTEM.INI
--------D-215D01-----------------------------
INT 21 U - DOS 3.1+ internal - COMMIT ALL FILES FOR SPECIFIED COMPUTER/PROCESS
    AX = 5D01h
    DS:DX -> DOS parameter list (see AX=5D00h), only computer ID and
        process ID fields used
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
Notes:    flushes buffers and updates directory entries for each file which has
      been written to; if remote file, calls INT 2F/AX=1107h
    the computer ID and process ID are stored but ignored under DOS 3.3
    not supported by DR-DOS 3.41 and 5.0; returns error code 01h
SeeAlso: AH=0Dh,AH=68h,INT 2F/AX=1107h
--------D-215D02-----------------------------
INT 21 U - DOS 3.1+ internal - SHARE.EXE - CLOSE FILE BY NAME
    AX = 5D02h
    DS:DX -> DOS parameter list (see AX=5D00h), only fields DX, DS,
        computer ID, and process ID used
    DPL's DS:DX -> ASCIZ name of file to close
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
Notes:    error unless SHARE is loaded (calls [SysFileTable-28h]) (see AH=52h)
    name must be canonical fully-qualified, such as returned by AH=60h
    not supported by DR-DOS 3.41 and 5.0; returns error code 01h
SeeAlso: AX=5D03h,AX=5D04h,AH=3Eh,AH=60h
--------D-215D03-----------------------------
INT 21 U - DOS 3.1+ internal - SHARE.EXE - CLOSE ALL FILES FOR GIVEN COMPUTER
    AX = 5D03h
    DS:DX -> DOS parameter list (see AX=5D00h), only computer ID used
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
Notes:    error unless SHARE is loaded (calls [SysFileTable-30h]) (see AH=52h)
    not supported by DR-DOS 3.41 and 5.0; returns error code 01h
SeeAlso: AX=5D02h,AX=5D04h
--------D-215D04-----------------------------
INT 21 U - DOS 3.1+ internal - SHARE.EXE - CLOSE ALL FILES FOR GIVEN PROCESS
    AX = 5D04h
    DS:DX -> DOS parameter list (see AX=5D00h), only computer ID and
        process ID fields used
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
Notes:    error unless SHARE is loaded (calls [SysFileTable-2Ch]) (see AH=52h)
    not supported by DR-DOS 3.41 and 5.0; returns error code 01h
SeeAlso: AX=5D02h,AX=5D03h,INT 2F/AX=111Dh
--------D-215D05-----------------------------
INT 21 U - DOS 3.1+ internal - SHARE.EXE - GET OPEN FILE LIST ENTRY
    AX = 5D05h
    DS:DX -> DOS parameter list (see AX=5D00h)
    DPL's BX = index of sharing record (see AH=52h)
    DPL's CX = index of SFT in sharing record's SFT list
Return: CF clear if successful
        ES:DI -> ASCIZ filename
        BX = network machine number of SFT's owner
        CX = number of locks held by SFT's owner
    CF set if either index out of range
        AX = 0012h (no more files)
Notes:    error unless SHARE is loaded (calls [SysFileTable-18h]) (see AH=52h)
    names are always canonical fully-qualified, such as returned by AH=60h
    not supported by DR-DOS 3.41 and 5.0, but does not return an error
SeeAlso: AH=5Ch,AH=60h
--------D-215D06-----------------------------
INT 21 U - DOS 3.0+ internal - GET ADDRESS OF DOS SWAPPABLE DATA AREA
    AX = 5D06h
Return: CF set on error
       AX = error code (see AH=59h)
    CF clear if successful
        DS:SI -> nonreentrant data area (includes all three DOS stacks)
        (critical error flag is first byte)
        CX = size in bytes of area which must be swapped while in DOS
        DX = size in bytes of area which must always be swapped
Notes:    the Critical Error flag is used in conjunction with the InDOS flag
      (see AH=34h) to determine when it is safe to enter DOS from a TSR
    setting CritErr flag allows use of functions 50h/51h from INT 28h under
      DOS 2.x by forcing use of correct stack
    swapping the data area allows reentering DOS unless DOS is in a
      critical section delimited by INT 2A/AH=80h and INT 2A/AH=81h,82h
    under DOS 4.0, AX=5D0Bh should be used instead of this function
    SHARE and other DOS utilities consult the byte at offset 04h in the
      DOS data segment (see INT 2F/AX=1203h) to determine the SDA format
      in use: 00h = DOS 3.x, 01h = DOS 4.0-6.0, other = error.
    DR-DOS 3.41+ supports this function, but the SDA format beyond the
      first 18h bytes is completely different from MS-DOS
SeeAlso: AX=5D0Bh,INT 2A/AH=80h,INT 2A/AH=81h,INT 2A/AH=82h

Format of DOS 3.10-3.30 Swappable Data Area:
Offset    Size    Description
 -34    BYTE    (DOS 3.10+) printer echo flag (00h off, FFh active)
 -31    BYTE    (DOS 3.30) current switch character
 -28    BYTE    (DOS 3.30) incremented on each INT 21/AX=5E01h call
 -27 16 BYTEs    (DOS 3.30) machine name set by INT 21/AX=5E01h
 -11  5 WORDs    zero-terminated list of offsets which need to be patched to
        enable critical-section calls (see INT 2A/AH=80h)
 -1    BYTE    unused padding
---start of actual SDA---
 00h    BYTE    critical error flag ("ErrorMode")
 01h    BYTE    InDOS flag (count of active INT 21 calls)
 02h    BYTE    drive on which current critical error occurred, or FFh
        (DR-DOS sets to drive number during INT 24, 00h otherwise)
 03h    BYTE    locus of last error
 04h    WORD    extended error code of last error
 06h    BYTE    suggested action for last error
 07h    BYTE    class of last error
 08h    DWORD    ES:DI pointer for last error
 0Ch    DWORD    current DTA
 10h    WORD    current PSP
 12h    WORD    stores SP across an INT 23
 14h    WORD    return code from last process termination (zerod after reading
        with AH=4Dh)
 16h    BYTE    current drive
 17h    BYTE    extended break flag
---remainder need only be swapped if in DOS---
 18h    WORD    value of AX on call to INT 21
 1Ah    WORD    PSP segment for sharing/network
 1Ch    WORD    network machine number for sharing/network (0000h = us)
 1Eh    WORD    first usable memory block found when allocating memory
 20h    WORD    best usable memory block found when allocating memory
 22h    WORD    last usable memory block found when allocating memory
 24h    WORD    memory size in paragraphs (used only during initialization)
 26h    WORD    last entry checked during directory search
 28h    BYTE    flag: INT 24 returned Fail
 29h    BYTE    flags: allowable INT 24 actions (passed to INT 24 in AH)
 2Ah    BYTE    directory flag (00h directory, 01h file)
 2Bh    BYTE    flag: FFh if Ctrl-Break termination, 00h otherwise
 2Ch    BYTE    flag: allow embedded blanks in FCB
 2Dh    BYTE    padding (unused)
 2Eh    BYTE    day of month
 2Fh    BYTE    month
 30h    WORD    year - 1980
 32h    WORD    number of days since 1-1-1980
 34h    BYTE    day of week (0 = Sunday)
 35h    BYTE    flag: console swapped during read from device
 36h    BYTE    flag: safe to call INT 28 if nonzero
 37h    BYTE    flag: if nonzero, INT 24 Abort turned into INT 24 Fail
        (set only during process termination)
 38h 26 BYTEs    device driver request header (see INT 2F/AX=0802h)
 52h    DWORD    pointer to device driver entry point (used in calling driver)
 56h 22 BYTEs    device driver request header for I/O calls
 6Ch 14 BYTEs    device driver request header for disk status check
 7Ah    DWORD    pointer to device I/O buffer???
 7Eh    WORD    ???
 80h    WORD    ???
 82h    BYTE    type of PSP copy (00h=simple for INT 21/AH=26h, FFh=make child)
 83h    BYTE    padding (unused)
 84h  3 BYTEs    24-bit user number (see AH=30h)
 87h    BYTE    OEM number (see AH=30h)
 88h    WORD    offset to error code conversion table for INT 25/INT 26
 8Ah  6 BYTEs    CLOCK$ transfer record (see AH=52h)
 90h    BYTE    device I/O buffer for single-byte I/O functions
 91h    BYTE    padding??? (unused)
 92h 128 BYTEs    buffer for filename
112h 128 BYTEs    buffer for filename
192h 21 BYTEs    findfirst/findnext search data block (see AH=4Eh)
1A7h 32 BYTEs    directory entry for found file (see AH=11h)
1C7h 81 BYTEs    copy of current directory structure for drive being accessed
218h 11 BYTEs    FCB-format filename for device name comparison
223h    BYTE    terminating NUL for above filename
224h 11 BYTEs    wildcard destination specification for rename (FCB format)
22Fh    BYTE    terminating NUL for above spec
230h    BYTE    ???
231h    WORD    destination file/directory starting sector
233h  5 BYTEs    ???
238h    BYTE    extended FCB file attribute
239h    BYTE    type of FCB (00h regular, FFh extended)
23Ah    BYTE    directory search attributes
23Bh    BYTE    file open/access mode
23Ch    BYTE    file found/delete flag
        bit 0: file found
        bit 4: file deleted
23Dh    BYTE    flag: device name found on rename, or file not found
23Eh    BYTE    splice flag (file name and directory name together)
23Fh    BYTE    flag indicating how DOS function was invoked
        (00h = direct INT 20/INT 21, FFh = server call AX=5D00h)
240h    BYTE    sector position within cluster
241h    BYTE    flag: translate sector/cluster (00h no, 01h yes)
242h    BYTE    flag: 00h if read, 01h if write
243h    BYTE    current working drive number
244h    BYTE    cluster factor
245h    BYTE    flag: cluster split mode
246h    BYTE    line edit (AH=0Ah) insert mode flag (nonzero = on)
247h    BYTE    canonicalized filename referred to existing file/dir if FFh
248h    BYTE    volume ID flag
249h    BYTE    type of process termination (00h-03h) (see AH=4Dh)
24Ah    BYTE    file create flag (00h = no)
24Bh    BYTE    value with which to replace first byte of deleted file's name
        (normally E5h, but 00h as described under INT 21/AH=13h)
24Ch    DWORD    pointer to Drive Parameter Block for critical error invocation
        temp: used during process termination
250h    DWORD    pointer to stack frame containing user registers on INT 21
254h    WORD    stores SP across INT 24
256h    DWORD    pointer to DOS Drive Parameter Block for ???
25Ah    WORD    saving partial cluster number
25Ch    WORD    temp: sector of work current cluster
25Eh    WORD    high part of cluster number (only low byte referenced)
260h    WORD    ??? temp
262h    BYTE    Media ID byte returned by AH=1Bh,1Ch
263h    BYTE    padding (unused)
264h    DWORD    pointer to device header
268h    DWORD    pointer to current SFT
26Ch    DWORD    pointer to current directory structure for drive being accessed
270h    DWORD    pointer to caller's FCB
274h    WORD    number of SFT to which file being opened will refer
276h    WORD    temporary storage for file handle
278h    DWORD    pointer to a JFT entry in process handle table (see AH=26h)
27Ch    WORD    offset in DOS DS of first filename argument
27Eh    WORD    offset in DOS DS of second filename argument
280h    WORD    offset of last component in pathname or FFFFh
282h    WORD    offset of transfer address to add
284h    WORD    last relative cluster within file being accessed
286h    WORD    temp: absolute cluster number being accessed
288h    WORD    directory sector number
28Ah    WORD    ??? current cluster number
28Ch    WORD    ??? current offset in file DIV bytes per sector
28Eh    WORD    current sector number
290h    WORD    current byte offset within sector
292h    DWORD    current offset in file
296h    DWORD    temp: file byte count
29Ah    WORD    temp: file byte count
29Ch    WORD    free file cluster entry
29Eh    WORD    last file cluster entry
2A0h    WORD    next file cluster number
2A2h    DWORD    number of bytes appended to file
2A6h    DWORD    pointer to current work disk buffer
2AAh    DWORD    pointer to working SFT
2AEh    WORD    used by INT 21 dispatcher to store caller's BX
2B0h    WORD    used by INT 21 dispatcher to store caller's DS
2B2h    WORD    temporary storage while saving/restoring caller's registers
2B4h    DWORD    pointer to prev call frame (offset 250h) if INT 21 reentered
        also switched to for duration of INT 24
2B8h 21 BYTEs    FindFirst search data for source file(s) of a rename operation
        (see AH=4Eh)
2CDh 32 BYTEs    directory entry for file being renamed (see AH=11h for format)
2EDh 331 BYTEs    critical error stack
   403h     35 BYTEs scratch SFT
438h 384 BYTEs    disk stack (functions greater than 0Ch, INT 25,INT 26)
5B8h 384 BYTEs    character I/O stack (functions 01h through 0Ch)
---DOS 3.2,3.3x only---
738h    BYTE    device driver lookahead flag (usually printer) (see AH=64h)
739h    BYTE    volume change flag
73Ah    BYTE    flag: virtual open
73Bh    BYTE    ???
--------D-215D07-----------------------------
INT 21 U - DOS 3.1+ network - GET REDIRECTED PRINTER MODE
    AX = 5D07h
Return: DL = mode
        00h redirected output is combined
        01h redirected output in separate print jobs
SeeAlso: AX=5D08h,AX=5D09h,INT 2F/AX=1125h
--------D-215D08-----------------------------
INT 21 U - DOS 3.1+ network - SET REDIRECTED PRINTER MODE
    AX = 5D08h
    DL = mode
        00h redirected output is combined
        01h redirected output placed in separate jobs, start new print job
        now
SeeAlso: AX=5D07h,AX=5D09h,INT 2F/AX=1125h
--------D-215D09-----------------------------
INT 21 U - DOS 3.1+ network - FLUSH REDIRECTED PRINTER OUTPUT
    AX = 5D09h
Notes:    forces redirected printer output to be printed, and starts a new print
      job
    this function is also supported by 10Net, which calls it Terminate All
      Spool Jobs, and does not flush if in "combine" mode
SeeAlso: AX=5D07h,AX=5D08h,INT 2F/AX=1125h
--------D-215D0A-----------------------------
INT 21 - DOS 3.1+ - SET EXTENDED ERROR INFORMATION
    AX = 5D0Ah
    DS:DX -> 11-word DOS parameter list (see AX=5D00h)
Return: nothing.  next call to AH=59h will return values from fields AX,BX,CX,
      DX,DI, and ES in corresponding registers
Notes:    documented for DOS 5+, but undocumented in earlier versions
    the MS-DOS Programmer's Reference incorrectly states that this call was
      introduced in DOS 4, and fails to mention that the ERROR structure
      passed to this function is a DOS parameter list.
BUG:    DR-DOS 3.41 and 5.0 read the value for ES from the DS field of the DPL;
      fortunately, MS-DOS ignores the DS field, allowing a generic routine
      which sets both DS and ES fields to the same value
SeeAlso: AH=59h
--------D-215D0B-----------------------------
INT 21 OU - DOS 4.x only internal - GET DOS SWAPPABLE DATA AREAS
    AX = 5D0Bh
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        DS:SI -> swappable data area list (see below)
Notes:    copying and restoring the swappable data areas allows DOS to be
      reentered unless it is in a critical section delimited by calls to
      INT 2A/AH=80h and INT 2A/AH=81h,82h
    SHARE and other DOS utilities consult the byte at offset 04h in the
      DOS data segment (see INT 2F/AX=1203h) to determine the SDA format
      in use: 00h = DOS 3.x, 01h = DOS 4.0-6.0, other = error.
    DOS 5+ use the SDA format listed below, but revert back to the DOS 3.x
      call for finding the SDA (see AX=5D06h)
SeeAlso: AX=5D06h,INT 2A/AH=80h,INT 2A/AH=81h,INT 2A/AH=82h,INT 2F/AX=1203h

Format of DOS 4.x swappable data area list:
Offset    Size    Description
 00h    WORD    count of data areas
 02h  N BYTEs    "count" copies of data area record
        Offset    Size    Description
         00h    DWORD    address
         04h    WORD    length and type
                bit 15 set if swap always, clear if swap in DOS
                bits 14-0: length in bytes

Format of DOS 4.0-6.0 swappable data area:
Offset    Size    Description
 -34    BYTE    printer echo flag (00h off, FFh active)
 -31    BYTE    current switch character (ignored by DOS 5+)
 -28    BYTE    incremented on each INT 21/AX=5E01h call
 -27 16 BYTEs    machine name set by INT 21/AX=5E01h
 -11  5 WORDs    zero-terminated list of offsets which need to be patched to
        enable critical-section calls (see INT 2A/AH=80h)
        (all offsets are 0D0Ch, but this list is still present for
        DOS 3.x compatibility)
 -1    BYTE    unused padding
---start of actual SDA---
 00h    BYTE    critical error flag ("ErrorMode")
 01h    BYTE    InDOS flag (count of active INT 21 calls)
 02h    BYTE    drive on which current critical error occurred or FFh
 03h    BYTE    locus of last error
 04h    WORD    extended error code of last error
 06h    BYTE    suggested action for last error
 07h    BYTE    class of last error
 08h    DWORD    ES:DI pointer for last error
 0Ch    DWORD    current DTA
 10h    WORD    current PSP
 12h    WORD    stores SP across an INT 23
 14h    WORD    return code from last process termination (zerod after reading
        with AH=4Dh)
 16h    BYTE    current drive
 17h    BYTE    extended break flag
 18h    BYTE    flag: code page switching
 19h    BYTE    flag: copy of previous byte in case of INT 24 Abort
---remainder need only be swapped if in DOS---
 1Ah    WORD    value of AX on call to INT 21
 1Ch    WORD    PSP segment for sharing/network
 1Eh    WORD    network machine number for sharing/network (0000h = us)
 20h    WORD    first usable memory block found when allocating memory
 22h    WORD    best usable memory block found when allocating memory
 24h    WORD    last usable memory block found when allocating memory
 26h    WORD    memory size in paragraphs (used only during initialization)
 28h    WORD    last entry checked during directory search
 2Ah    BYTE    flag: nonzero if INT 24 Fail
 2Bh    BYTE    flags: allowable INT 24 responses (passed to INT 24 in AH)
 2Ch    BYTE    flag: do not set directory if nonzero
 2Dh    BYTE    flag: program aborted by ^C
 2Eh    BYTE    flag: allow embedded blanks in FCB
 2Fh    BYTE    padding (unused)
 30h    BYTE    day of month
 31h    BYTE    month
 32h    WORD    year - 1980
 34h    WORD    number of days since 1-1-1980
 36h    BYTE    day of week (0 = Sunday)
 37h    BYTE    flag: console swapped during read from device
 38h    BYTE    flag: safe to call INT 28 if nonzero
 39h    BYTE    flag: abort currently in progress, turn INT 24 Abort into Fail
 3Ah 30 BYTEs    device driver request header (see INT 2F/AX=0802h) for
        device calls
 58h    DWORD    pointer to device driver entry point (used in calling driver)
 5Ch 22 BYTEs    device driver request header for I/O calls
 72h 14 BYTEs    device driver request header for disk status check
 80h    DWORD    pointer to device I/O buffer
 84h    WORD    ???
 86h    WORD    ??? (0)
 88h    BYTE    type of PSP copy (00h=simple for INT 21/AH=26h, FFh=make child)
 89h    DWORD    start offset of file region to lock/unlock
 8Dh    DWORD    length of file region to lock/unlock
 91h    BYTE    padding (unused)
 92h  3 BYTEs    24-bit user number (see AH=30h)
 95h    BYTE    OEM number (see AH=30h)
 96h  6 BYTEs    CLOCK$ transfer record (see AH=52h)
 9Ch    BYTE    device I/O buffer for single-byte I/O functions???
 9Dh    BYTE    padding???
 9Eh 128 BYTEs    buffer for filename
11Eh 128 BYTEs    buffer for filename
19Eh 21 BYTEs    findfirst/findnext search data block (see AH=4Eh)
1B3h 32 BYTEs    directory entry for found file (see AH=11h)
1D3h 88 BYTEs    copy of current directory structure for drive being accessed
22Bh 11 BYTEs    FCB-format filename for device name comparison
236h    BYTE    terminating NUL for above filename
237h 11 BYTEs    wildcard destination specification for rename (FCB format)
242h    BYTE    terminating NUL for above spec
243h    BYTE    ???
244h    WORD    ???
246h  5 BYTEs    ???
24Bh    BYTE    extended FCB file attributes
24Ch    BYTE    type of FCB (00h regular, FFh extended)
24Dh    BYTE    directory search attributes
24Eh    BYTE    file open/access mode
24Fh    BYTE    ??? flag bits
250h    BYTE    flag: device name found on rename, or file not found
251h    BYTE    splice flag??? (file name and directory name together)
252h    BYTE    flag indicating how DOS function was invoked
        (00h = direct INT 20/INT 21, FFh = server call AX=5D00h)
253h    BYTE    ???
254h    BYTE    ???
255h    BYTE    ???
256h    BYTE    ???
257h    BYTE    ???
258h    BYTE    ???
259h    BYTE    ???
25Ah    BYTE    canonicalized filename referred to existing file/dir if FFh
25Bh    BYTE    ???
25Ch    BYTE    type of process termination (00h-03h)
25Dh    BYTE    ???
25Eh    BYTE    ???
25Fh    BYTE    ???
260h    DWORD    pointer to Drive Parameter Block for critical error invocation
264h    DWORD    pointer to stack frame containing user registers on INT 21
268h    WORD    stores SP???
26Ah    DWORD    pointer to DOS Drive Parameter Block for ???
26Eh    WORD    segment of disk buffer
270h    WORD    ???
272h    WORD    ???
274h    WORD    ???
276h    WORD    ???
278h    BYTE    Media ID byte returned by AH=1Bh,1Ch
279h    BYTE    ??? (doesn't seem to be referenced)
27Ah    DWORD    pointer to ???
27Eh    DWORD    pointer to current SFT
282h    DWORD    pointer to current directory structure for drive being accessed
286h    DWORD    pointer to caller's FCB
28Ah    WORD    SFT index to which file being opened will refer
28Ch    WORD    temporary storage for file handle
28Eh    DWORD    pointer to a JFT entry in process handle table (see AH=26h)
292h    WORD    offset in DOS DS of first filename argument
294h    WORD    offset in DOS DS of second filename argument
296h    WORD    ???
298h    WORD    ???
29Ah    WORD    ???
29Ch    WORD    ???
29Eh    WORD    ???
2A0h    WORD    ???
2A2h    WORD    ??? directory cluster number???
2A4h    DWORD    ???
2A8h    DWORD    ???
2ACh    WORD    ???
2AEh    DWORD    offset in file???
2B2h    WORD    ???
2B4h    WORD    bytes in partial sector
2B6h    WORD    number of sectors
2B8h    WORD    ???
2BAh    WORD    ???
2BCh    WORD    ???
2BEh    DWORD    number of bytes appended to file
2C2h    DWORD    pointer to ??? disk buffer
2C6h    DWORD    pointer to ??? SFT
2CAh    WORD    used by INT 21 dispatcher to store caller's BX
2CCh    WORD    used by INT 21 dispatcher to store caller's DS
2CEh    WORD    temporary storage while saving/restoring caller's registers
2D0h    DWORD    pointer to prev call frame (offset 264h) if INT 21 reentered
        also switched to for duration of INT 24
2D4h    WORD    open mode/action for INT 21/AX=6C00h
2D6h    BYTE    ??? (set to 00h by INT 21h dispatcher, 02h when a read is
        performed, and 01h or 03h by INT 21/AX=6C00h)
2D7h    WORD    ??? apparently unused
2D9h    DWORD    stored ES:DI for AX=6C00h
2DDh    WORD    extended file open action code (see AX=6C00h)
2DFh    WORD    extended file open attributes (see AX=6C00h)
2E1h    WORD    extended file open file mode (see AX=6C00h)
2E3h    DWORD    pointer to filename to open (see AX=6C00h)
2E7h    WORD    ???
2E9h    WORD    ???
2EBh    BYTE    ???
2ECh    WORD    stores DS during call to [List-of-Lists + 37h]
2EEh    WORD    ???
2F0h    BYTE    ???
2F1h    WORD    ??? bit flags
2F3h    DWORD    pointer to user-supplied filename
2F7h    DWORD    pointer to ???
2FBh    WORD    stores SS during call to [List-of-Lists + 37h]
2FDh    WORD    stores SP during call to [List-of-Lists + 37h]
2FFh    BYTE    flag, nonzero if stack switched in calling [List-of-Lists+37h]
300h 21 BYTEs    FindFirst search data for source file(s) of a rename operation
        (see AH=4Eh)
315h 32 BYTEs    directory entry for file being renamed (see AH=11h)
335h 331 BYTEs    critical error stack
480h 384 BYTEs    disk stack (functions greater than 0Ch, INT 25,INT 26)
600h 384 BYTEs    character I/O stack (functions 01h through 0Ch)
780h    BYTE    device driver lookahead flag (usually printer) (see AH=64h)
781h    BYTE    volume change flag
782h    BYTE    flag: virtual open
783h    BYTE    ???
784h    WORD    ???
786h    WORD    ???
788h    WORD    ???
78Ah    WORD    ???
--------D-215E00-----------------------------
INT 21 - DOS 3.1+ network - GET MACHINE NAME
    AX = 5E00h
    DS:DX -> 16-byte buffer for ASCIZ machine name
Return: CF clear if successful
        CH = validity
        00h name invalid
        nonzero valid
            CL = NetBIOS number for machine name
            DS:DX buffer filled with blank-paded name
    CF set on error
        AX = error code (01h) (see AH=59h)
Note:    supported by OS/2 v1.3+ compatibility box, PC-NFS
SeeAlso: AX=5E01h
--------N-215E00-----------------------------
INT 21 - 10NET v5.0 - GET MACHINE NAME
    AX = 5E00h
Return: CL = redirector's NetBIOS name number
    ES:DI -> network node ID
SeeAlso: AX=5E01h"10NET"
--------D-215E01CH00-------------------------
INT 21 - DOS 3.1+ network - SET MACHINE NAME
    AX = 5E01h
    CH = 00h undefine name (make it invalid)
       <> 0     define name
    CL = name number
    DS:DX -> 15-character blank-padded ASCIZ name
SeeAlso: AX=5E00h
--------N-215E01-----------------------------
INT 21 - 10NET v5.0 - GET LOCAL 10NET CONFIGURATION TABLE
    AX = 5E01h
    CX = length of buffer
    DS:DX -> buffer for 10Net configuration table
SeeAlso: AX=5E00h"10NET",INT 6F/AH=02h,INT 6F/AH=03h

Format of 10Net Configuration Table:
Offset    Size    Description
 00h  8 BYTEs    user name
 08h 15 BYTEs    node ID
 17h  3 BYTEs    unique portion of Ethernet address
 1Ah    BYTE    Who group number
 1Bh    WORD    services mask (see below)
 1Dh    DWORD    serial number
 21h    BYTE    maximum concurrent users with same serial number allowed on net
 22h    BYTE    chat mask (see below)
 23h    BYTE    internal system bits (see below)
 24h  9 BYTEs    version number in format MM.mm.xxx
 2Dh    BYTE    flag: 01h if machine is a PS/2
 2Eh    BYTE    flag: 03h if 80386
 2Fh    BYTE    spool termination mode: 01h concatenate, 02h truncate
        (see AX=5D09h)
 30h    WORD    autospool timeout in clock ticks
 32h    WORD    monitor timeout in clock ticks
 34h    WORD    unused
 36h    WORD    chat timeout in clock ticks
 38h    WORD    netBIOS session timeout in half-seconds
 3Ah    WORD    datagram send timeout in seconds
 3Ch    WORD    keyboard value for initiating chat mode
 3Eh    WORD    Who timeout in clock ticks
 40h    BYTE    flag: 01h if server should process rom NetBIOS Post return
 41h    BYTE    flag: 01h if FCBs should be recycled
 42h  3 BYTEs    signature "DBG"
 45h    BYTE    last interrupt (21h or 6Fh)
 46h    BYTE    last INT 21 AH value
 47h    BYTE    last INT 6F AH value
 48h    WORD    last item posted
 4Ah    WORD    last item free-posted
 4Ch    WORD    last item handled by server
 4Eh    WORD    last redirector send NCB
 50h    WORD    last redirector receive NCB
 52h  4 BYTEs    signature "TABL"
 56h    WORD    offset of datagram buffer table header
 58h    WORD    offset of chat buffer table header
 5Ah    WORD    offset of Raw buffer table header
 5Ch    WORD    offset of Workstation buffer table header
 5Eh    WORD    offset of server receive-any table header
 60h    WORD    offset of Tiny buffer table header
 62h    WORD    offset of zero-length buffer table (NCBs)
 64h    WORD    offset of Rdr (Redirector Mount) table header
 66h    WORD    offset of Ntab (Redirector Session) table header
 68h    WORD    offset of FCB table header
 6Ah    WORD    offset of user file handle table header
 6Ch    WORD    offset of workstation printer RDR extension table header
 6Eh    WORD    offset of server shared device table header
 70h    WORD    offset of server connection table header
 72h    WORD    offset of server login table header
 74h    WORD    offset of server file table header
 76h    WORD    offset of server shared file table header
 78h    WORD    offset of server record lock table header
 7Ah    WORD    offset of remote printer claim table header
 7Ch    WORD    offset of remote printer device table header
 7Eh    WORD    offset of print server mount table header
 80h    WORD    offset of print server sessions table header
 82h    WORD    offset of print server print job structure table header
 84h    WORD    offset of print server pooled device table header
 86h    WORD    size of workstation buffer
 88h    WORD    size of server receive-any buffer
 8Ah    WORD    size of server raw I/O buffer
 8Ch  6 BYTEs    reserved
 92h    DWORD    pointer to profile pathname
 96h    BYTE    datagram retry count
 97h    BYTE    NetBIOS LAN adapter number
 98h  6 BYTEs    physical Ethernet address
 9Eh    BYTE    NetBIOS server name number
 9Fh    BYTE    NetBIOS redirector name number
 A0h    BYTE    10Net interrupt number
 A1h    BYTE    flag: chat is loaded
 A2h    BYTE    flag: INT 6F APIs permanently loaded
 A3h    BYTE    flag: file security present
 A4h    WORD    reserved
 A6h    BYTE    fixed mount bitmask for drives A:-H:
 A7h    BYTE    reserved
 A8h    WORD    10Net system flags (see below)
 AAh    BYTE    monitor flags (see below)
 ABh  5 BYTEs    reserved
 B0h    WORD    offset of monitor timer block
 B2h    WORD    offset of server timer block
 B4h    WORD    offset of chat timer block
 B6h    WORD    timer chain
 B8h  4 BYTEs    signature "TALS"
 BCh    WORD    number of 10Net sends
 BEh    WORD    number of 10Net receives
 C0h    WORD    number of no-buffer conditions
 C2h    WORD    number of dropped posted messages
 C4h    WORD    number of server NCB errors
 C6h    WORD    number of redirector NCB errors
 C8h    WORD    number of datagram send/receive errors
 CAh    WORD    number of dropped Whos
 CCh    WORD    number of dropped submits
 CEh    WORD    number of session aborts
 D0h    BYTE    number of NetBIOS interface-busy errors
 D1h    BYTE    last NetBIOS bad post command
 D2h    BYTE    last NetBIOS bad redirector command
 D3h    BYTE    do send datagram send/receive error command
 D4h    DWORD    -> DOS system parameter table
 D8h    WORD    number of DOS physical drives
 DAh    WORD    offset of DOS PSP field in DOS data segment
 DCh    WORD    offset of in-DOS flag in DOS data segment
 DEh    WORD    DOS data segment
 E0h    WORD    offset of DOS SFT in DOS data segment
 E2h    WORD    offset of number-of-physical-units field in DOS data segment
 E4h    WORD    10Net code segment
 E6h    WORD    10Net data segment
 E8h    WORD    10Net common server segment
 EAh    WORD    10Net file server segment
 ECh    WORD    10Net print server segment
 EEh    WORD    10Net remote printer segment
Note:    documentation lists field at offset D0h as a WORD, but all following
      offsets are as though it were a BYTE; if it is indeed a WORD, all
      offsets after D0h must be increased by one byte

Format of 10Net Table Header:
Offset    Size    Description
 -16  4 BYTEs    table identifier
 -12    WORD    peak number of tables allocated
 -10    WORD    number of tables currently in use
 -8    WORD    total number of tables
 -6    WORD    size of each table
 -4    WORD    offset of first allocated table
 -2    WORD    offset of first free table

Bitfields for services mask:
 bit 0    workstation
 bit 1    file server
 bit 2    print queue server
 bit 3    de-spool server

Bitfields for chat mask:
 bit 0    chat permitted
 bit 1    bell enabled
 bit 2    chat keyboard initiated
 bit 3    in INT 16 handler
 bit 4    in Get Input
 bit 5    display has timed out
 bit 6    chat is idle

Bitfields for internal system bits:
 bit 0    submit permitted
 bit 1    submit initiated
 bit 2    submit executing
 bit 3    internal client call/chat/spool/autospool
 bit 4    in spool termination
 bit 5    print permitted
 bit 6    waiting for keyboard input

Bitfields for 10Net System Flags:
 bit 0    in NetBIOS
 bit 1    processing INT 28
 bit 2    is server
 bit 3    in net user-DOS function
 bit 4    in DOS user-DOS function
 bit 5    in net for user non-DOS function
 bit 6    in server DOS function
 bit 7    in server non-DOS function
 bit 8    in terminate
 bit 10    in user on server request
 bit 13    in DOS for user on server
 bit 14    disable critical error handler

Bitfields for Monitor Flags:
 bit 0    waiting for monitor response
 bit 4    in monitor get-input routine
 bit 5    monitor display timeout
 bit 6    sensing for escape key
--------D-215E02-----------------------------
INT 21 - DOS 3.1+ network - SET NETWORK PRINTER SETUP STRING
    AX = 5E02h
    BX = redirection list index (see AX=5F02h)
    CX = length of setup string
    DS:SI -> setup string
Return: CF clear if successful
    CF set on error
        AX = error code (01h) (see AH=59h)
Note:    also supported by 10NET v5.0
SeeAlso: AX=5E03h,INT 2F/AX=111Fh
--------D-215E03-----------------------------
INT 21 - DOS 3.1+ network - GET NETWORK PRINTER SETUP STRING
    AX = 5E03h
    BX = redirection list index (see AX=5F02h)
    ES:DI -> 64-byte buffer for setup string
Return: CF clear if successful
        CX = length of setup string
        ES:DI buffer filled
    CF set on error
        AX = error code (01h) (see AH=59h)
Note:    also supported by 10NET v5.0, but 10NET is documented as using DS:SI
      instead of ES:DI
SeeAlso: AX=5E02h,INT 2F/AX=111Fh
--------D-215E04-----------------------------
INT 21 - DOS 3.1+ network - SET PRINTER MODE
    AX = 5E04h
    BX = redirection list index (see AX=5F02h)
    DX = mode
        bit 0: set if binary, clear if text (tabs expanded to blanks)
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
Note:    calls INT 2F/AX=111Fh with 5E04h on stack
SeeAlso: AX=5E05h"DOS",INT 2F/AX=111Fh
--------N-215E04-----------------------------
INT 21 - 10NET v5.0 - INITIATE PRINT JOB
    AX = 5E04h
    BX = zero-based redirection list index (see AX=5F02h)
    DS:DX -> extended workstation printer setup structure (see below)
Return: CF clear if successful
    CF set on error
        AX = error code (see AH=59h)
SeeAlso: AX=5E05h"10NET",AX=5E06h"10NET"

Format of extended workstation printer setup structure:
Offset    Size    Description
 00h    BYTE    notification flags (see below)
 01h    BYTE    job control mask (see below)
 02h    WORD    days to retain file
 04h    WORD    test print length
 06h    BYTE    number of copies to print
 07h    BYTE    compression algorithm
 08h    BYTE    tab width (00h = don't expand)
 09h    BYTE    initiation type (00h normal, 01h non-spooled)
 0Ah 38 BYTEs    job start operation notification instructions
 30h 32 BYTEs    comment for job
 50h 64 BYTEs    output filename or non-spooled file

Bitfields for notification flags:
 bit 0    user at print start
 bit 1    operator at start, with reply
 bit 2    user at print completion
 bit 3    operator at completion, with reply
 bit 4    user on queue switch
 bit 5    operator on queue switch, with reply
 bit 6    user on print error

Bitfields for job control mask:
 bit 0    print banner page
 bit 1    eject page at end of job
 bit 2    mark as "held" (queue but don't print)
 bit 3    rush job (queue at top)
 bit 4    overwrite file with zeros before deletion
 bit 5    hyperspool if possible
--------D-215E05-----------------------------
INT 21 - DOS 3.1+ network - GET PRINTER MODE
    AX = 5E05h
    BX = redirection list index (see AX=5F02h)
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        DX = printer mode (see AX=5E04h)
Note:    calls INT 2F/AX=111Fh with 5E05h on stack
SeeAlso: AX=5E04h"DOS",INT 2F/AX=111Fh
--------N-215E05-----------------------------
INT 21 - 10NET v5.0 - TERMINATE PRINT JOB
    AX = 5E05h
    BX = zero-based redirection list index (see AX=5F02h)
Return: CF clear if successful
    CF set on error
        AX = error code (see AH=59h)
Note:    this call resets the spool termination mode to "truncate"
      (see AX=5D08h)
SeeAlso: AX=5E04h"10NET",AX=5E06h
--------N-215E06-----------------------------
INT 21 - 10NET v5.0 - GET/SET 10NET WORKSTATION PRINTER SETUP STRUCTURE
    AX = 5E06h
    BX = zero-based redirection list index (see AX=5F02h)
    CX = operation (06h set, 07h get)
    DS:DX -> buffer for setup structure (same as first nine bytes of
        workstation printer setup) (see AX=5E04h"10NET")
Return: CF clear if successful
        DS:DX buffer updated on get
    CF set on error
        AX = error code (see AH=59h)
SeeAlso: AX=5E04h"10NET",AX=5E05h"10NET"
--------D-215F00-----------------------------
INT 21 - DOS 3.1+ network - GET REDIRECTION MODE
    AX = 5F00h
    BL = redirection type
        03h printer
        04h disk drive
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        BH = redirection state
        00h off
        01h on
Note:    calls INT 2F/AX=111Eh with AX on top of the stack
SeeAlso: AX=5F01h,INT 2F/AX=111Eh
--------D-215F01-----------------------------
INT 21 - DOS 3.1+ network - SET REDIRECTION MODE
    AX = 5F01h
    BL = redirection type
        03h printer
        04h disk drive
    BH = redirection state
        00h off
        01h on
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
Notes:    when redirection is off, the local device (if any) rather than the
      remote device is used
    calls INT 2F/AX=111Eh with AX on top of the stack
SeeAlso: AX=5F00h,INT 2F/AX=111Eh
--------D-215F02-----------------------------
INT 21 - DOS 3.1+ network - GET REDIRECTION LIST ENTRY
    AX = 5F02h
    BX = zero-based redirection list index
    CX = 0000h (LANtastic)
    DS:SI -> 16-byte buffer for ASCIZ local device name
    ES:DI -> 128-byte buffer for ASCIZ network name
Return: CF clear if successful
        BH = device status
        00h valid
        01h invalid
        BL = device type
        03h printer
        04h disk drive
        CX = user data previously set with AX=5F03h
        DS:SI and ES:DI buffers filled
        DX,BP destroyed
    CF set on error
        AX = error code (01h,12h) (see AH=59h)
Notes:    this function is passed through to INT 2F/AX=111Eh by the DOS kernel
    error code 12h is returned if BX is greater than the size of the list
    also supported by Banyan VINES, PC-NFS, LANtastic, and 10NET
SeeAlso: AX=5F03h,INT 2F/AX=111Eh
--------D-215F03-----------------------------
INT 21 - DOS 3.1+ network - REDIRECT DEVICE
    AX = 5F03h
    BL = device type
        03h printer
        04h disk drive
    CX = user data to save
        0000h for LANtastic
        4E57h ("NW") for NetWare 4.0 requester
    DS:SI -> ASCIZ local device name (16 bytes max)
    ES:DI -> ASCIZ network name + ASCIZ password (128 bytes max total)
Return: CF clear if successful
    CF set on error
        AX = error code (01h,03h,05h,08h,0Fh,12h) (see AH=59h)
Notes:    if device type is disk drive, DS:SI must point at either a null string
      or a string consisting the drive letter followed by a colon; if a
      null string, the network attempts to access the destination without
      redirecting a local drive
    the DOS kernel calls INT 2F/AX=111Eh with AX on top of the stack
    also supported by Banyan VINES, LANtastic, and 10NET
SeeAlso: AX=5F02h,AX=5F04h,INT 2F/AX=111Eh
--------D-215F04-----------------------------
INT 21 - DOS 3.1+ network - CANCEL REDIRECTION
    AX = 5F04h
    DS:SI -> ASCIZ local device name or path
    CX = 4E57h ("NW") for NetWare 4.0 requester
Return: CF clear if successful
    CF set on error
        AX = error code (01h,03h,05h,08h,0Fh,12h) (see AH=59h)
Notes:    the DS:SI string must be either a local device name, a drive letter
      followed by a colon, or a network directory beginning with two
      backslashes
    the DOS kernel calls INT 2F/AX=111Eh with AX on top of the stack
    also supported by Banyan VINES, LANtastic, and 10NET
SeeAlso: AX=5F03h,INT 2F/AX=111Eh
--------D-215F05-----------------------------
INT 21 - DOS 4+ network - GET EXTENDED REDIRECTION LIST ENTRY
    AX = 5F05h
    BX = redirection list index
    DS:SI -> buffer for ASCIZ source device name
    ES:DI -> buffer for destination ASCIZ network path
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        AX = server's network process ID handle (10NET)
        BH = device status flag (bit 0 clear if valid)
        BL = device type (03h if printer, 04h if drive)
        CX = stored parameter value (user data) from AX=5F03h
        BP = NETBIOS local session number
        DS:SI buffer filled
        ES:DI buffer filled
Notes:    the local session number allows sharing the redirector's session number
    if an error is caused on the NETBIOS LSN, the redirector may be unable
      to correctly recover from errors
    the DOS kernel calls INT 2F/AX=111Eh with AX on top of the stack
    supported by DR-DOS 5.0
    also supported by 10NET v5.0
SeeAlso: AX=5F06h"Network",INT 2F/AX=111Eh
--------O-215F05-----------------------------
INT 21 - STARLITE architecture - MAP LOCAL DRIVE LETTER TO REMOTE FILE SYSTEM
    AX = 5F05h
    DL = drive number (0=A:)
    DS:SI -> ASCIZ name of the object to map the drive to
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
SeeAlso: AX=5F06h"STARLITE"
--------N-215F06-----------------------------
INT 21 U - Network - GET FULL REDIRECTION LIST
    AX = 5F06h
    ???
Return: ???
Notes:    similar to AX=5F02h and AX=5F05h, but also returns redirections
      excluded from those calls for various reasons
    calls INT 2F/AX=111Eh with AX on top of the stack
SeeAlso: AX=5F05h"DOS",INT 2F/AX=111Eh
--------O-215F06-----------------------------
INT 21 - STARLITE architecture - UNMAP DRIVE LETTER
    AX = 5F06h
    DL = drive to be unmapped (0=A:)
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
SeeAlso: AX=5F05h"STARLITE"
--------D-215F07-----------------------------
INT 21 - DOS 5+ - ENABLE DRIVE
    AX = 5F07h
    DL = drive number (0=A:)
Return: CF clear if successful
    CF set on error
        AX = error code (0Fh) (see AH=59h)
Note:    simply sets the "valid" bit in the drive's CDS
SeeAlso: AH=52h,AX=5F08h"DOS"
--------O-215F07-----------------------------
INT 21 - STARLITE architecture - MAKE NAMED OBJECT AVAILABLE ON NETWORK
    AX = 5F07h
    DS:SI -> ASCIZ name of object to offer to network
    ES:DI -> ASCIZ name under which object will be known on the network
        MUST begin with three slashes
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
SeeAlso: AX=5F08h"STARLITE"
--------D-215F08-----------------------------
INT 21 - DOS 5+ - DISABLE DRIVE
    AX = 5F08h
    DL = drive number (0=A:)
Return: CF clear if successful
    CF set on error
        AX = error code (0Fh) (see AH=59h)
Note:    simply clears the "valid" bit in the drive's CDS
SeeAlso: AH=52h,AX=5F07h"DOS"
--------O-215F08-----------------------------
INT 21 - STARLITE architecture - REMOVE GLOBAL NETWORK NAME OF OBJECT
    AX = 5F08h
    DS:SI -> ASCIZ network name (not local name) of object to unshare
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
SeeAlso: AX=5F07h"STARLITE"
--------O-215F09-----------------------------
INT 21 - STARLITE architecture - BIND TO NETWORK DEVICE
    AX = 5F09h
    DS:DX -> ASCIZ name of the device driver to attach to
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
Note:    the STARLITE distributed file system can attach to multiple networks
      simultaneously
SeeAlso: AX=5F0Ah
--------O-215F0A-----------------------------
INT 21 - STARLITE architecture - DETACH FROM NETWORK DEVICE
    AX = 5F0Ah
    DS:DX -> ASCIZ name of device driver to detach from
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
SeeAlso: AX=5F09h
--------N-215F30-----------------------------
INT 21 U - LAN Manager Enhanced DOS - ???
    AX = 5F30h
    ???
Return: ???
--------N-215F32-----------------------------
INT 21 u - Named Pipes - LOCAL DosQNmPipeInfo
    AX = 5F32h
    BX = handle
    CX = size of _PIPEINFO structure
    DX = level (must be 0001h)
    DS:SI -> _PIPEINFO structure (see below)
Return: CF clear if successful
        _PIPEINFO structure filled in
    CF set on error
        AX = error code
Note:    this function was introduced by LAN Manager but is also supported by
      the Novell DOS Named Pipe Extender, Banyan VINES, OS/2 Virtual DOS
      Machines, and others
SeeAlso: AX=5F33h,AX=5F34h

Format of _PIPEINFO structure:
Offset    Size    Description
 00h    WORD    size of outgoing buffer
 02h    WORD    size of incoming buffer
 04h    BYTE    maximum number of instances allowed
 05h    BYTE    current number of instances
 06h    BYTE    length of the name (including terminating NUL)
 07h  N BYTEs    name
--------N-215F33-----------------------------
INT 21 u - Named Pipes - LOCAL DosQNmPHandState
    AX = 5F33h
    BX = handle
Return: CF clear if successful
        AH = pipe mode bit mask (see below)
        AL = maximum number of instances
    CF set on error
        AX = error code
Note:    this function was introduced by LAN Manager but is also supported by
      the Novell DOS Named Pipe Extender, Banyan VINES, OS/2 Virtual DOS
      Machines, and others
SeeAlso: AX=5F32h,AX=5F34h

Bitfields for pipe mode:
 bit 7    set if nonblocking, clear if blocking
 bit 6    set if server end, clear if client end
 bit 2    set if write in message mode, clear if write in byte mode
 bit 0    set if read in message mode, clear if read in byte mode
--------N-215F34-----------------------------
INT 21 u - Named Pipes - LOCAL DosSetNmPHandState
    AX = 5F34h
    BX = handle
    CX = pipe mode bit mask
        bit 15: set if nonblocking, clear if blocking
        bit     8: set if read in message mode, clear if read in byte mode
Return: CF clear if successful
    CF set if error
        AX = error code
Note:    this function was introduced by LAN Manager but is also supported by
      the Novell DOS Named Pipe Extender, Banyan VINES, OS/2 Virtual DOS
      Machines, and others
SeeAlso: AX=5F32h,AX=5F33h,AX=5F36h
--------N-215F35-----------------------------
INT 21 u - Named Pipes - LOCAL DosPeekNmPipe
    AX = 5F35h
    BX = handle
    CX = buffer length
    DS:SI -> buffer
Return: CF clear if successful
        CX = bytes read
        SI = bytes left in the pipe
        DX = bytes left in the current message
        DI = pipe status
        0001h disconnected
        0002h listening
        0003h connected
        0004h closing
    CF set if error
        AX = error code
Note:    this function was introduced by LAN Manager but is also supported by
      the Novell DOS Named Pipe Extender, Banyan VINES, OS/2 Virtual DOS
      Machines, and others
SeeAlso: AX=5F38h,AX=5F39h,AX=5F51h
--------N-215F36-----------------------------
INT 21 u - Named Pipes - LOCAL DosTransactNmPipe
    AX = 5F36h
    BX = handle
    CX = in buffer length
    DS:SI -> in buffer
    DX = out buffer length
    ES:DI -> out buffer
Return: CF clear if successful
        CX = bytes read
    CF set on error
        AX = error code
Note:    this function was introduced by LAN Manager but is also supported by
      the Novell DOS Named Pipe Extender, Banyan VINES, OS/2 Virtual DOS
      Machines, and others
SeeAlso: AX=5F34h,AX=5F37h
--------N-215F37-----------------------------
INT 21 u - Named Pipes - DosCallNmPipe
    AX = 5F37h
    DS:SI -> DosCallNmPipe stack frame (see below)
Return: CF clear if successful
        CX = bytes read
    CF set on error
        AX = error code
Note:    this function was introduced by LAN Manager but is also supported by
      the Novell DOS Named Pipe Extender, Banyan VINES, OS/2 Virtual DOS
      Machines, and others
SeeAlso: AX=5F36h,AX=5F38h

Format of DosCallNmPipe stack frame:
Offset    Size    Description
 00h    DWORD    timeout
 04h    DWORD    -> bytes read WORD (not used!!)
 08h    WORD    out buffer length
 0Ah    DWORD    address of out buffer
 0Eh    WORD    in buffer length
 10h    DWORD    address of in buffer
 14h    DWORD    address of pipe name
--------N-215F38-----------------------------
INT 21 u - Named Pipes - LOCAL DosWaitNmPipe
    AX = 5F38h
    DS:DX -> pipe name
    BX:CX = timeout value
Return: CF clear if successful
    CF set if error
        AX = error code
Note:    this function was introduced by LAN Manager but is also supported by
      the Novell DOS Named Pipe Extender, Banyan VINES, OS/2 Virtual DOS
      Machines, and others
SeeAlso: AX=5F37h,AX=5F39h
--------N-215F39-----------------------------
INT 21 U - Named Pipes - LOCAL DosRawReadNmPipe
    AX = 5F39h
    BX = handle
    CX = buffer length
    DS:DX -> buffer
Return: CF clear if successful
        CX = bytes read
    CF set if error
        AX = error code
Notes:    this function was introduced by LAN Manager but is also supported by
      the Novell DOS Named Pipe Extender, Banyan VINES, OS/2 Virtual DOS
      Machines, and others
    not documented in the LAN Manager Toolkit
SeeAlso: AX=5F35h,AX=5F3Ah,INT 2F/AX=1186h
--------N-215F3A-----------------------------
INT 21 U - Named Pipes - LOCAL DosRawWriteNmPipe
    AX = 5F3Ah
    BX = handle
    CX = buffer length
    DS:DX -> buffer
Return: CF clear if successful
        CX = bytes written
    CF set if error
        AX = error code
Notes:    this function was introduced by LAN Manager but is also supported by
      the Novell DOS Named Pipe Extender, Banyan VINES, OS/2 Virtual DOS
      Machines, and others
    not documented in the LAN Manager Toolkit
SeeAlso: AX=5F39h,AX=5F3Bh,INT 2F/AX=118Fh
--------N-215F3B-----------------------------
INT 21 u - LAN Manager Enhanced DOS - NetHandleSetInfo
    AX = 5F3Bh
    BX = handle
    CX = handle_info_1 structure length or sizeof DWORD
    DI = parameter number to set
        0000h all
        0001h number of milliseconds
        0002h number of characters
    DS:DX -> handle_info_1 structure (DI=0000h) (see below)
        or DWORD (DI=0001h or 0002h)
    SI = level of information (0001h)
Return: CF clear if successful
        CX = total bytes available
    CF set if error
        AX = error code
SeeAlso: AX=5F3Ch

Format of handle_info_1 structure:
Offset    Size    Description
 00h    DWORD    number of milliseconds which workstations collects data before
        it sends the data to the named pipe
 04h    DWORD    number of characters which workstations collects before it
        sends the data to the named pipe
--------N-215F3C-----------------------------
INT 21 u - LAN Manager Enhanced DOS - NetHandleGetInfo
    AX = 5F3Ch
    BX = handle
    CX = length of handle_info_1 structure
    DS:DX -> handle_info_1 structure (see AX=5F3Bh)
    SI = level of information (must be 0001h)
Return: CF clear if successful
        CX = total bytes available
    CF set if error
        AX = error code
SeeAlso: AX=5F3Bh
--------N-215F3D-----------------------------
INT 21 U - LAN Manager Enhanced DOS - WRITE MAILSLOT???
    AX = 5F3Dh
    ???
Return: ???
--------N-215F3E-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetSpecialSMB
    AX = 5F3Eh
    ???
Return: ???
Note:    This function is not documented anywhere in the LAN Manager 2.x Toolkit
      but was documented in LAN Manager 1.x manuals.
--------N-215F3F-----------------------------
INT 21 U - LAN Manager Enhanced DOS - REMOTE API CALL
    AX = 5F3Fh
    CX = api number
    ES:DI -> data descriptor
    ES:SI -> parameter descriptor
    ES:DX -> auxiliary descriptor (if DX <> 0)
    ???
Return: ???
--------N-215F40-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetMessageBufferSend
    AX = 5F40h
    DS:DX -> NetMessageBufferSend parameter structure (see below)
Return: AX = error code

Format of NetMessageBufferSend parameter structure:
Offset    Size    Description
 00h    DWORD    -> recipient name (name for specific user, name* for domain
            name wide, * for broadcast)
 04h    DWORD    -> buffer
 08h    WORD    length of buffer
--------N-215F41-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetServiceEnum
    AX = 5F41h
    BL = level of detail (0000h, 0001h or 0002h)
    CX = buffer length
    ES:DI -> buffer of service_info_0, service_info_1, or service_info_2
        (see below)
Return: CF clear if successful
        CX = entries read
        DX = total available
    CF set on error
        AX = error code

Format of service_info_0 structure:
Offset    Size    Description
 00h 16 BYTEs    name

Format of service_info_1 structure:
Offset    Size    Description
 00h 16 BYTEs    name
 10h    WORD    status bitmask (see below)
 12h    DWORD    status code (see below)
        (also see Microsoft LAN Manager Programmer's Reference)
 16h    WORD    process id

Format of service_info_2 structure:
Offset    Size    Description
 00h 16 BYTEs    name
 10h    WORD    status bitmask (see below)
 12h    DWORD    status code (see below)
 16h    WORD    process id
 18h 64 BYTEs    text

Bitfields for status bitmask:
 bits 0,1    00 uninstall
        01 install pending
        10 uninstall pending
        11 installed
 bits 2,3    00 active
        01 Continue pending
        10 Pause pending
        11 paused
 bit 4    uninstallable
 bit 5    pausable
 bit 8    disk redirector paused
 bit 9    spooled device redirector paused (printing)
 bit 10 communication device redirector paused

Values for status code:
 high word
    3051 Bad parameter value
    3052 A parameter is missing
    3053 An unknown parameter was specified
    3054 The resource is insufficient
    3055 Configuration is faulty
    3056 An MS-DOS or MS OS/2 error occured
    3057 An internal error occured
    3058 An ambiguous parameter name was given
    3059 A duplicate parameter exists
    3060 The service was terminated by NetSeviceControl when it did not respond
    3061 The service program file could not be executed
    3062 The subservice failed to start
    3063 There is a conflict in the value or use of these parameters
    3064 There is a problem with the file
 low word
    3070 There is insufficient memory
    3071 There is insufficeient disk space
    3072 Unable to create thread
    3073 Unable to create process
    3074 A security failure occured
    3075 There is bad or missing default path
    3076 Network software is not installed
    3077 Server software is not installed
    3078 The server could not access the UAS database
    3079 The action requires user-level security
    3080 The log directory is invalid
    3081 The LAN group specificed could not be used
    3082 The computername is being used as a message alias on another computer
    3083 The workstation failed to announce the servername
    3084 The user accounts system is not configured properly
--------N-215F42-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetServiceControl
    AX = 5F42h
    DH = opcode
        00h interrogate status
        01h pause
        02h continue
        03h uninstall
    DL = argument
        01h disk resource
        02h print resource
        04h communications resource (not implemented for DOS)
    ES:BX -> NetServiceControl parameter structure (see below)
Return: CF clear if successful
    CF set on error
        AX = error code

Format of NetServiceControl parameter structure:
Offset    Size    Description
 00h    DWORD    -> service name
 04h    WORD    result buffer size
 06h    DWORD    -> result buffer as service_info_2 structure
--------N-215F43-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL DosPrintJobGetId
    AX = 5F43h
    BX = handle of remote print job
    CX = size of PRIDINFO struture
    ES:DI -> PRIDINFO structure (see below)
Return: CF clear if successful
        PRIDINFO filled in
    CF set on error
        AX = error code

Format of PRIDINFO structure:
Offset    Size    Description
 00h    WORD    job id
 02h 16 BYTEs    server name
 12h 13 BYTEs    queue name
 1Fh  1 BYTE    pad
--------N-215F44-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetWkstaGetInfo
    AX = 5F44h
    BX = information level (00h, 01h, or 0Ah)
    CX = buffer size
    ES:DI = buffer in which to store info
Return: AX = error code
    DX = amount of buffer used (or required)
SeeAlso: AX=5F45h,AX=5F49h
--------N-215F45-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetWkstaSetInfo
    AX = 5F45h
    BX = level (0000h or 0001h)
    CX = buffer size
    DX = parameter to set
    ES:DI -> buffer
Return: CF clear if successful
    CF set if error
        AX = error code
SeeAlso: AX=5F44h
--------N-215F46-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetUseEnum
    AX = 5F46h
    BX = level (0000h or 0001h)
    CX = size of buffer
    ES:DI -> buffer of use_info_0 or use_info_1 structures (see below)
Return: CF clear if successful
        CX = entries read
        DX = total available entries
    CF set if error
        AX = error code
SeeAlso: AX=5F47h,AX=5F48h,AX=5F4Ch

Format of use_info_0 structure:
Offset    Size    Description
 00h  9 BYTEs    local device name
 09h    BYTE    padding
 0Ah    DWORD    -> remote device name in UNC form \\server\share

Format of use_info_1 structure:
Offset    Size    Description
 00h  9 BYTEs    Local device name
 09h    BYTE    padding
 0Ah    DWORD    -> remote device name in UNC form \\server\share
 0Eh    DWORD    -> password
 12h    WORD    ignored
 14h    WORD    use type (-1 wildcard, 0 disk, 1 print, 2 com, 3 ipc)
 16h    WORD    ignored
 18h    WORD    ignored
--------N-215F47-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetUseAdd
    AX = 5F47h
    BX = level (0001h)
    CX = size of use_info_1 structure
    ES:DI -> use_info_1 structure (see AX=5F46h)
Return: CF clear on success
    CF set on error
        AX = error code
SeeAlso: AX=5F46h,AX=5F48h
--------N-215F48-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetUseDel
    AX = 5F48h
    BX = force level
        0000h no force
        0001h force
        0002h lots of force
    ES:DI -> buffer as either the local device name or UNC remote name
Return: CF clear on success
    CF set on error
        AX = error code
SeeAlso: AX=5F46h,AX=5F48h,AX=5F49h
--------N-215F49-----------------------------
INT 21 u - LAN Manager Enhanced DOS - NetUseGetInfo
    AX = 5F49h
    DS:DX -> NetUseGetInfo parameter structure
Return: CF clear on success
        DX = total available
    CF set on error
        AX = error code
SeeAlso: AX=5F44h,AX=5F47h

Format of NetUseGetInfo parameter structure:
Offset    Size    Description
 00h    DWORD    pointer to either the local device name or UNC remote name
 04h    WORD    level of information (0000h or 0001h)
 06h    DWORD    pointer to buffer of use_info_0 or use_info_1 structures
 0Ah    WORD    length of buffer
--------N-215F4A-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetRemoteCopy
    AX = 5F4Ah
    DS:DX -> NetRemoteCopy parameter structure
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5F4Bh

Format of NetRemoteCopy parameter structure:
Offset    Size    Description
 00h    DWORD    -> source name as UNC
 04h    DWORD    -> destination name as UNC
 08h    DWORD    -> source password
 0Ch    DWORD    -> destination password
 10h    WORD    destination open bitmap
        if destination path exists
            0000h open fails
            0001h file is appended
            0002h file is overwritten
        if destination path doesn't exist
            0000h open fails
            0010h file is created
 12h    WORD    copy control bitmap (see below)
 14h    DWORD    -> copy_info buffer
 18h    WORD    length of copy_info buffer

Bitfields for copy control:
 bit 0    destination must be a file
 bit 1    destination must be a directory
 bit 2    destination is opened in ascii mode instead of binary
 bit 3    source is opened in ascii mode instead of binary
 bit 4    verify all write operations
--------N-215F4B-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetRemoteMove
    AX = 5F4Bh
    DS:DX -> NetRemoteMove parameter structure
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5F4Ah

Format of NetRemoteMove parameter structure:
Offset    Size    Description
 00h    DWORD    -> source name as UNC
 04h    DWORD    -> destination name as UNC
 08h    DWORD    -> source password
 0Ch    DWORD    -> destination password
 10h    WORD    destination open bitmap
        if destination path exists
            0000h open fails
            0001h file is appended
            0002h file is overwritten
        if destination path doesn't exist
            0000h open fails
            0010h file is created
 12h    WORD    move control bitmap
            0001h destination must be a file
            0002h destination must be a directory
 14h    DWORD    -> move_info buffer
 18h    WORD    length of move_info buffer
--------N-215F4C-----------------------------
INT 21 u - LAN Manager Enhanced DOS - LOCAL NetServerEnum
    AX = 5F4Ch
    BX = level (0000h or 0001h)
    CX = buffer length
    ES:DI -> buffer in which to store information
Return: CF clear if successful
        ES:DI -> server_info_X structures (depending on level) (see below)
        BX = entries read
        CX = total entries available
    CF set on error
        AX = error code
Notes:    this function is also supported by the Novell DOS Named Pipe Extender
    this function has been obseleted by NetServerEnum2
SeeAlso: AX=5F53h

Format of server_info_0 structure:
Offset    Size    Description
 00h 16 BYTEs    name

Format of server_info_1 structure:
Offset    Size    Description
 00h 16 BYTEs    name
 10h    BYTE    major version in lower nibble
 11h    BYTE    minor version
 12h    DWORD    server type bitmask (see below)
 16h    DWORD    -> comment string

Bitfields for server type:
 bit 0    workstation
 bit 1    server
 bit 2    SQL server
 bit 3    primary domain controller
 bit 4    backup domain controller
 bit 5    time server
 bit 6    Apple File Protocol (AFP) server
 bit 7    Novell server
 bit 8    Domain Member (v2.1+)
 bit 9    Print Queue server (v2.1+)
 bit 10 Dialin server (v2.1+)
 bit 11 Unix server (v2.1+)
--------N-215F4D-----------------------------
INT 21 u - LAN Manager Enhanced DOS - DosMakeMailslot
    AX = 5F4Dh
    BX = message size
    CX = mailslot size (must be bigger than message size by at least 1)
               (minimum 1000h, maximum FFF6h)
               (buffer must be 9 bytes bigger than this)
    DS:SI -> name
    ES:DI -> memory buffer
Return: CF clear if successful
        AX = handle
    CF set on error
        AX = error code
SeeAlso: AX=5F4Eh,AX=5F4Fh,AX=5F50h,AX=5F51h
--------N-215F4E-----------------------------
INT 21 u - LAN Manager Enhanced DOS - DosDeleteMailslot
    AX = 5F4Eh
    BX = handle
Return: CF clear if successful
        ES:DI -> memory to be freed (allocated during DosMakeMailslot)
    CF set on error
        AX = error code
SeeAlso: AX=5F4Dh,AX=5F4Fh
--------N-215F4F-----------------------------
INT 21 u - LAN Manager Enhanced DOS - DosMailslotInfo
    AX = 5F4Fh
    BX = handle
Return: CF clear if successful
        AX = max message size
        BX = mailslot size
        CX = next message size
        DX = next message priority
        SI = number of messages waiting
    CF set on error
        AX = error code
SeeAlso: AX=5F4Dh,AX=5F4Eh,AX=5F50h
--------N-215F50-----------------------------
INT 21 u - LAN Manager Enhanced DOS - DosReadMailslot
    AX = 5F50h
    BX = handle
    DX:CX = timeout
    ES:DI -> buffer
Return: CF clear if successful
        AX = bytes read
        CX = next item's size
        DX = next item's priority
    CF set on error
        AX = error code
SeeAlso: AX=5F4Dh,AX=5F4Fh,AX=5F51h,AX=5F52h
--------N-215F51-----------------------------
INT 21 u - LAN Manager Enhanced DOS - DosPeekMailslot
    AX = 5F51h
    BX = handle
    ES:DI -> buffer
Return: CF clear if successful
        AX = bytes read
        CX = next item's size
        DX = next item's priority
    CF set on error
        AX = error code
SeeAlso: AX=5F35h,AX=5F4Fh,AX=5F50h,AX=5F52h
--------N-215F52-----------------------------
INT 21 u - LAN Manager Enhanced DOS - DosWriteMailslot
    AX = 5F52h
    BX = class
    CX = length of buffer
    DX = priority
    ES:DI -> DosWriteMailslot parameter structure (see below)
    DS:SI -> mailslot name
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5F4Fh,AX=5F50h,AX=5F51h

Format of DosWriteMailslot parameter structure:
Offset    Size    Description
 00h    DWORD    timeout
 04h    DWORD    -> buffer
--------N-215F53-----------------------------
INT 21 u - LAN Manager Enhanced DOS - NetServerEnum2
    AX = 5F53h
    DS:SI -> NetServerEnum2 parameter structure (see below)
Return: CF clear if successful
        BX = entries read
        CX = total entries available
    CF set on error
        AX = error code
SeeAlso: AX=5F4Ch

Format of NetServerEnum2 parameter structure:
Offset    Size    Description
 00h    WORD    level (0000h or 0001h)
 02h    DWORD    -> buffer as array of server_info_??? structures
 06h    WORD    length of buffer
 08h    DWORD    server type bitmask (see below)
 0Ch    DWORD    -> Domain name (may be 0000h:0000h for all local domains)

Bitfields for server type:
 bit 0    workstation
 bit 1    server
 bit 2    SQL server
 bit 3    primary domain controller
 bit 4    backup domain controller
 bit 5    time server
 bit 6    Apple File Protocol (AFP) server
 bit 7    Novell server
 bit 8    Domain Member (v2.1+)
 bit 9    Print Queue server (v2.1+)
 bit 10 Dialin server (v2.1+)
 bit 11 Unix server (v2.1+)
Note:    set all bits (FFFFFFFFh) for All Types

Format of server_info_0 structure:
Offset    Size    Description
 00h 16 BYTEs    name

Format of server_info_1 structure:
Offset    Size    Description
 00h 16 BYTEs    name
 10h    BYTE    major version in lower nibble
 11h    BYTE    minor version
 12h    DWORD    server type (bits 0-11) (see above)
 16h    DWORD    -> comment string
--------N-215F55----------------------------
INT 21 U - LAN Manager Enhanced DOS - KILL ALL CONNECTIONS???
    AX = 5F55h
    BX = ???
Return: CF clear if successful
    CF set on error
        AX = error code
--------N-215F80-----------------------------
INT 21 - LANtastic - GET LOGIN ENTRY
    AX = 5F80h
    BX = login entry index (0-based)
    ES:DI -> 16-byte buffer for machine name
Return: CF clear if successful
        buffer filled with machine name ("\\" prefix removed)
        DL = adapter number (v3+)
    CF set on error
        AX = error code
Note:    the login entry index corresponds to the value BX used in AX=5F83h
SeeAlso: AX=5F83h
--------N-215F81-----------------------------
INT 21 - LANtastic - LOGIN TO SERVER
    AX = 5F81h
    ES:DI -> ASCIZ login path followed immediately by ASCIZ password
    BL = adapter number
        FFh try all valid adapters
        00h-07h try only specified adapter
Return: CF clear if successful
    CF set on error
        AX = error code
Notes:    login path is of form "\\machine\username"
    if no password is used, the string at ES:DI must be terminated with
      three NULs for compatibility with LANtastic v3.0.
SeeAlso: AX=5F82h,AX=5F84h
--------N-215F82-----------------------------
INT 21 - LANtastic - LOGOUT FROM SERVER
    AX = 5F82h
    ES:DI -> ASCIZ server name (in form "\\machine")
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5F81h,AX=5F88h,AX=5FCBh
--------N-215F83-----------------------------
INT 21 - LANtastic - GET USERNAME ENTRY
    AX = 5F83h
    BX = login entry index (0-based)
    ES:DI -> 16-byte buffer for username currently logged into
Return: CF clear if successful
        DL = adapter number (v3+)
    CF set on error
        AX = error code
Note:    the login entry index corresponds to the value BX used in AX=5F80h
SeeAlso: AX=5F80h
--------N-215F84-----------------------------
INT 21 - LANtastic - GET INACTIVE SERVER ENTRY
    AX = 5F84h
    BX = server index not currently logged into
    ES:DI -> 16-byte buffer for server name which is available for logging
        in to ("\\" prefix omitted)
Return: CF clear if successful
        DL = adapter number to non-logged in server is on
    CF set on error
        AX = error code
SeeAlso: AX=5F81h
--------N-215F85-----------------------------
INT 21 - LANtastic - CHANGE PASSWORD
    AX = 5F85h
    ES:DI -> buffer containing "\\machine\oldpassword" 00h "newpassword"00h
Return: CF clear if successful
    CF set on error
        AX = error code
Notes:    must be logged into the named machine
    this function is illegal for group accounts
--------N-215F86-----------------------------
INT 21 - LANtastic - DISABLE ACCOUNT
    AX = 5F86h
    ES:DI -> ASCIZ machine name and password in form "\\machine\password"
Return: CF clear if successful
    CF set on error
        AX = error code
Note:    must be logged into the named machine and concurrent logins set to 1
      by NET_MGR.  Requires system manager to re-enable account.
--------N-215F87-----------------------------
INT 21 - LANtastic v3+ - GET ACCOUNT
    AX = 5F87h
    DS:SI -> 128-byte buffer for account information (see below)
    ES:DI -> ASCIZ machine name in form "\\machine"
Return: CF clear if successful
    CF set on error
        AX = error code
    BX destroyed
Note:    must be logged into the specified machine

Format of user account structure:
Offset    Size    Description
 00h 16 BYTEs    blank-padded username (zero-padded for v4.x)
 10h 16 BYTEs    reserved (00h)
 20h 32 BYTEs    user description
 40h    BYTE    privilege bits (see below)
 41h    BYTE    maximum concurrent users
 42h 42 BYTEs    bit map for disallowed half hours, beginning on Sunday
        (bit set if half-hour not an allowed time)
 6Ch    WORD    internal (0002h)
 6Eh  2 WORDs    last login time
 72h  2 WORDs    account expiration date (MS-DOS-format year/month:day)
 76h  2 WORDs    password expiration date (0 = none)
 7Ah    BYTE    number of days to extend password after change (1-31)
        00h if no extension required
---v3.x---
 7Bh  5 BYTEs    reserved
---v4.x---
 7Bh    BYTE    storage for first letter of user name when deleted (first
        character is changed to 00h when deleting account)
 7Ch    BYTE    extended privileges
 7Dh  3 BYTEs    reserved

Bitfields for privilege bits:
 bit 7    bypass access control lists
 bit 6    bypass queue protection
 bit 5    treat as local process
 bit 4    bypass mail protection
 bit 3    allow audit entry creation
 bit 2    system manager
 bit 0    user cannot change password
--------N-215F88-----------------------------
INT 21 - LANtastic v4.0+ - LOGOUT FROM ALL SERVERS
    AX = 5F88h
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5F82h
--------N-215F97-----------------------------
INT 21 - LANtastic - COPY FILE
    AX = 5F97h
    CX:DX = number of bytes to copy (FFFFFFFFh = entire file)
    SI = source file handle
    DI = destination file handle
Return: CF clear if successful
        DX:AX = number of bytes copied
    CF set on error
        AX = error code
Note:    copy is performed by server
--------N-215F98-----------------------------
INT 21 - LANtastic - SEND UNSOLICITED MESSAGE
    AX = 5F98h
    DS:SI -> message buffer (see below)
Return: CF clear if successful
    CF set on error
        AX = error code
Note:    v4.1- return no errors
SeeAlso: AX=5F99h

Format of message buffer:
Offset    Size    Description
 00h    BYTE    reserved
 01h    BYTE    message type
        00h general
        01h server warning
        02h-7Fh reserved
        80h-FFh user-defined
 02h 16 BYTEs    ASCIZ destination machine name
 12h 16 BYTEs    ASCIZ server name which user must be logged into
 22h 16 BYTEs    ASCIZ user name
 32h 16 BYTEs    ASCIZ originating machine name (filled in when received)
 42h 80 BYTEs    message text
--------N-215F99-----------------------------
INT 21 - LANtastic - GET LAST RECEIVED UNSOLICITED MESSAGE
    AX = 5F99h
    ES:DI -> messsage buffer (see AX=5F98h for format)
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5F98h
--------N-215F9A-----------------------------
INT 21 - LANtastic - GET MESSAGE PROCESSING FLAGS
    AX = 5F9Ah
Return: CF clear if successful
        DL = bits describing processing for received unsolicited messages
        bit 0: beep before message is delivered
        bit 1: deliver message to message service
        bit 2: pop up message automatically (v3+)
    CF set on error
        AX = error code
SeeAlso: AX=5F9Bh,AX=5F9Ch,AX=5F9Dh
--------N-215F9B-----------------------------
INT 21 - LANtastic - SET MESSAGE PROCESSING FLAG
    AX = 5F9Bh
    DL = bits describing processing for received unsolicited messages
         (see AX=5F9Ah)
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5F9Ah,AX=5F9Eh
--------N-215F9C-----------------------------
INT 21 - LANtastic v3+ - POP UP LAST RECEIVED MESSAGE
    AX = 5F9Ch
    CX = time to leave on screen in clock ticks
    DH = 0-based screen line on which to place message
Return: CF clear if successful
    CF set on error
        AX = error code (0Bh)
Notes:    the original screen contents are restored when the message is removed
    the message will not appear, and an error will be returned, if the
      screen is in a graphics mode
SeeAlso: AX=5F9Ah
--------N-215F9D-----------------------------
INT 21 - LANtastic v4.1+ - GET REDIRECTOR CONTROL BITS
    AX = 5F9Dh
Return: DL = redirector control bits
        bit 7: set to notify on print job completion
SeeAlso: AX=5F9Ah,AX=5F9Eh
--------N-215F9E-----------------------------
INT 21 - LANtastic v4.1+ - SET REDIRECTOR CONTROL BITS
    AX = 5F9Eh
    DL = redirector control bits (see AH = 5F9Dh)
Return: nothing
SeeAlso: AX=5F9Bh,AX=5F9Dh
--------N-215FA0-----------------------------
INT 21 - LANtastic - GET QUEUE ENTRY
    AX = 5FA0h
    BX = queue entry index (0000h is first entry)
    DS:SI -> buffer for queue entry (see below)
    ES:DI -> ASCIZ server name in form "\\name"
Return: CF clear if successful
    CF set on error
        AX = error code
    BX = entry index for next queue entry (BX-1 is current index)
SeeAlso: AX=5FA1h,AX=5FA2h

Values for status of entry:
 00h    empty
 01h    being updated
 02h    being held
 03h    waiting for despool
 04h    being despooled
 05h    canceled
 06h    spooled file could not be accessed
 07h    destination could not be accessed
 08h    rush job

Values for type of entry:
 00h    printer queue file
 01h    message
 02h    local file
 03h    remote file
 04h    to remote modem
 05h    batch processor file

Format of queue entry:
Offset    Size    Description
 00h    BYTE    status of entry (see above)
 01h    DWORD    size of spooled file
 05h    BYTE    type of entry (see above)
 06h    BYTE    output control
        bit 6: don't delete (for mail)
        bit 5: mail file contains voice mail (v3+)
        bit 4: mail message has been read
        bit 3: response has been requested for this mail
 07h    WORD    number of copies
 09h    DWORD    sequence number of queue entry
 0Dh 48 BYTEs    pathname of spooled file
 3Dh 16 BYTEs    user who spooled file
 4Dh 16 BYTEs    name of machine from which file was spooled
 5Dh    WORD    date file was spooled (see AX=5700h)
 5Fh    WORD    time file was spooled (see AX=5700h)
 61h 17 BYTEs    ASCIZ destination device or user name
 72h 48 BYTEs    comment field
--------N-215FA1-----------------------------
INT 21 - LANtastic - SET QUEUE ENTRY
    AX = 5FA1h
    BX = handle of opened queue entry
    DS:SI -> queue entry (see AX=5FA0h)
Return: CF clear if successful
    CF set on error
        AX = error code
Notes:    the only queue entry fields which may be changed are output control,
      number of copies, destination device, and comment
    the handle in BX is that from a create or open (INT 21/AH=3Ch,3Dh)
      call on the file "\\server\\@MAIL" or "\\server\@name" (for
      printer queue entries)
SeeAlso: AX=5FA0h,AX=5FA2h,AX=5FA9h
--------N-215FA2-----------------------------
INT 21 - LANtastic - CONTROL QUEUE
    AX = 5FA2h
    BL = control command
        00h start despooling (privileged)
        01h halt despooling (privileged)
        02h halt despooling at end of job (privileged)
        03h pause despooler at end of job (privileged)
        04h print single job (privileged)
        05h restart current job (privileged)
        06h cancel the current job
        07h hold queue entry
        08h release a held queue entry
        09h make queue entry a rushed job (privileged)
    CX:DX = sequence number to control (commands 06h-09h)
    DX = physical printer number (commands 00h-05h)
        00h-02h LPT1-LPT3
        03h,04h COM1,COM2
        other    all printers
    ES:DI -> ASCIZ server name in form "\\machine"
Return: CF clear if successful
    CF set on error
        AX = error code
--------N-215FA3-----------------------------
INT 21 - LANtastic v3+ - GET PRINTER STATUS
    AX = 5FA3h
    BX = physical printer number (00h-02h = LPT1-LPT3, 03h-04h = COM1-COM2)
    DS:SI -> buffer for printer status (see below)
    ES:DI -> ASCIZ server name in form "\\machine"
Return: CF clear if successful
    CF set on error
        AX = error code
    BX = next physical printer number
Note:    you must be logged in to the specified server

Format of printer status:
Offset    Size    Description
 00h    BYTE    printer state
        bit 7: printer paused
        bits 0-6: 0 printer disabled
              1 will stop at end of job
              2 print multiple jobs
 01h    WORD    queue index of print job being despooled
        FFFFh if not despooling--ignore all following fields
 03h    WORD    actual characters per second being output
 05h    DWORD    number of characters actually output so far
 09h    DWORD    number of bytes read from spooled file so far
 0Dh    WORD    copies remaining to print
--------N-215FA4-----------------------------
INT 21 - LANtastic v3+ - GET STREAM INFO
    AX = 5FA4h
    BX = 0-based stream index number
    DS:SI -> buffer for stream information (see below)
    ES:DI -> ASCIZ machine name in form "\\machine"
Return: CF clear if successful
    CF set on error
        AX = error code
    BX = next stream number
SeeAlso: AX=5FA5h

Format of stream information:
Offset    Size    Description
 00h    BYTE    queueing of jobs for logical printer (0=disabled,other=enabled)
 01h 11 BYTEs    logical printer resource template (may contain ? wildcards)
--------N-215FA5-----------------------------
INT 21 - LANtastic v3+ - SET STREAM INFO
    AX = 5FA5h
    BX = 0-based stream index number
    DS:SI -> buffer containing stream information (see AX=5FA4h)
    ES:DI -> ASCIZ machine name in form "\\machine"
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5FA4h
--------N-215FA7-----------------------------
INT 21 - LANtastic - CREATE USER AUDIT ENTRY
    AX = 5FA7h
    DS:DX -> ASCIZ reason code (max 8 bytes)
    DS:SI -> ASCIZ variable reason string (max 128 bytes)
    ES:DI -> ASCIZ machine name in form "\\machine"
Return: CF clear if successful
    CF set on error
        AX = error code
Note:    you must be logged in to the specified server and have the "U"
      privilege to execute this call
--------N-215FA9-----------------------------
INT 21 - LANtastic v4.1+ - SET EXTENDED QUEUE ENTRY
    AX = 5FA9h
    BX = handle of opened queue entry
    DS:SI -> queue entry (see AX=5FA0h)
Return: CF clear if successful
    CF set on error
        AX = error code
Note:    functions exactly the same as AX=5FA1h except the spooled filename is
      also set.  This call supports direct despooling.
SeeAlso: AX=5FA1h
--------N-215FB0-----------------------------
INT 21 - LANtastic - GET ACTIVE USER INFORMATION
    AX = 5FB0h
    BX = server login entry index
    DS:SI -> buffer for active user entry (see below)
    ES:DI -> ASCIZ machine name in form "\\server"
Return: CF clear if successful
    CF set on error
        AX = error code
    BX = next login index
SeeAlso: AX=5FB2h

Format of active user entry:
Offset    Size    Description
 00h    WORD    virtual circuit number
 02h    BYTE    login state (see below)
 03h    BYTE    last command issued (see below)
 04h  5 BYTEs    number of I/O bytes (40-bit unsigned number)
 09h  3 BYTEs    number of server requests (24-bit unsigned)
 0Ch 16 BYTEs    name of user who is logged in
 1Ch 16 BYTEs    name of remote logged in machine
 2Ch    BYTE    extended privileges (v4+???)
        bit 0: user cannot change his password
 2Dh    WORD    time left in minutes (0000h = unlimited) (v4+???)

Bitfields for login state:
 bit 0    fully logged in
 bit 1    remote program load login
 bit 2    user has system manager privileges
 bit 3    user can create audit entries
 bit 4    bypass mail protection
 bit 5    treat as local process
 bit 6    bypass queue protection
 bit 7    bypass access control lists

Values for last command:
 00h    login
 01h    process termination
 02h    open file
 03h    close file
 04h    create file
 05h    create new file
 06h    create unique file
 07h    commit data to disk
 08h    read file
 09h    write file
 0Ah    delete file
 0Bh    set file attributes
 0Ch    lock byte range
 0Dh    unlock byte range
 0Eh    create subdirectory
 0Fh    remove subdirectory
 10h    rename file
 11h    find first matching file
 12h    find next matching file
 13h    get disk free space
 14h    get a queue entry
 15h    set a queue entry
 16h    control the queue
 17h    return login information
 18h    return link description
 19h    seek on file
 1Ah    get server's time
 1Bh    create audit entry
 1Ch    open file in multitude of modes
 1Dh    change password
 1Eh    disable account
 1Fh    local server file copy
---v3+---
 20h    get username from account file
 21h    translate server's logical path
 22h    make indirect file
 23h    get indirect file contents
 24h    get physical printer status
 25h    get logical print stream info
 26h    set logical print stream info
 27h    get user's account record
---v4+---
 28h    request server shutdown
 29h    cancel server shutdown
 2Ah    stuff server's keyboard
 2Bh    write then commit data to disk
 2Ch    set extended queue entry
 2Dh    terminate user from server
 2Eh    enable/disable logins
 2Fh    flush server caches
 30h    change username
 31h    get extended queue entry
    (same as get queue, but can return named fields blanked)
--------N-215FB1-----------------------------
INT 21 - LANtastic - GET SHARED DIRECTORY INFORMATION
    AX = 5FB1h
    DS:SI -> 64-byte buffer for link description
    ES:DI -> ASCIZ machine and shared directory name in form
         "\\machine\shared-resource"
Return: CF clear if successful
        CX = access control list privileges for requesting user (see below)
    CF set on error
        AX = error code

Bitfields for access control list:
 bit 4    (I) allow expansion of indirect files
 bit 5    (A) allow attribute changing
 bit 6    (P) allow physical access to device
 bit 7    (E) allow program execution
 bit 8    (N) allow file renaming
 bit 9    (K) allow directory deletion
 bit 10 (D) allow file deletion
 bit 11 (L) allow file/directory lookups
 bit 12 (M) allow directory creation
 bit 13 (C) allow file creation
 bit 14 (W) allow open for write and writing
 bit 15 (R) allow open for read and reading
--------N-215FB2-----------------------------
INT 21 - LANtastic v3+ - GET USERNAME FROM ACCOUNT FILE
    AX = 5FB2h
    BX = username entry index (0 for first)
    DS:SI -> 16-byte buffer for username
    ES:DI -> ASCIZ server name in form "\\machine"
Return: CF clear if successful
    CF set on error
        AX = error code
    BX = next queue entry index
SeeAlso: AX=5FB0h
--------N-215FB3-----------------------------
INT 21 - LANtastic v3+ - TRANSLATE PATH
    AX = 5FB3h
    DS:SI -> 128-byte buffer for ASCIZ result
    ES:DI -> full ASCIZ path, including server name
    DX = types of translation to be performed
        bit 0: expand last component as indirect file
        bit 1: return actual path relative to server's physical disk
Return: CF clear if successful
    CF set on error
        AX = error code
Note:    always expands any indirect files along the path
SeeALso: AX=5FB4h,INT 21/AH=60h
--------N-215FB4-----------------------------
INT 21 - LANtastic v3+ - CREATE INDIRECT FILE
    AX = 5FB4h
    DS:SI -> 128-byte buffer containing ASCIZ contents of indirect file
    ES:DI -> full ASCIZ path of indirect file to create, incl machine name
Return: CF clear if successful
    CF set on error
        AX = error code
Note:    the contents of the indirect file may be any valid server-relative path
SeeAlso: AX=5FB3h,AX=5FB5h
--------N-215FB5-----------------------------
INT 21 - LANtastic v3+ - GET INDIRECT FILE CONTENTS
    AX = 5FB5h
    DS:SI -> 128-byte buffer for ASCIZ indirect file contents
    ES:DI -> full ASCIZ path of indirect file
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5FB4h
--------N-215FB6-----------------------------
INT 21 - LANtastic v4.1+ - SET AUTO-LOGIN DEFAULTS
    AX = 5FB6h
    ES:DI -> pointer to ASCIZ default user name, immediately followed by
        ASCIZ password
    BL = adapter number to use for default login attempt
        FFh try all valid adapters
        00h-05h try adapter 0-5 explicitly
Return: CF clear if successful
    CF set on error
        AX = error code
Notes:    call with ES:DI -> two nulls to disable auto-login
SeeAlso: AX=5FB7h
--------N-215FB7-----------------------------
INT 21 - LANtastic v4.1+ - GET AUTO-LOGIN DEFAULTS
    AX = 5FB7h
    ES:DI -> pointer to 16-byte buffer to store ASCIZ auto-login user name
Return: CF clear if successful
        DL = adapter number used for default login attempt
        FFh all valid adapters will be tried
        00h-05h specified adapter will be tried explicitly
    CF set on error
        AX = error code
SeeAlso: AX=5F81h,AX=5FB6h
--------N-215FC0-----------------------------
INT 21 - LANtastic - GET TIME FROM SERVER
    AX = 5FC0h
    DS:SI -> time block (see below)
    ES:DI -> ASCIZ server name to get time from
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AH=E7h

Format of time block:
Offset    Size    Description
 00h    WORD    year
 02h    BYTE    day
 03h    BYTE    month
 04h    BYTE    minutes
 05h    BYTE    hour
 06h    BYTE    hundredths of second
 07h    BYTE    second
--------N-215FC8-----------------------------
INT 21 - LANtastic v4.0+ - SCHEDULE SERVER SHUTDOWN
    AX = 5FC8h
    ES:DI -> ASCIZ server name in form "\\machine"
    DS:SI -> ASCIZ reason string (80 characters)
    CX = number of minutes until shutdown (0 = immediate)
    DX = option flags (see below)
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5FC9h

Bitfields for option flags:
 bit 0    auto reboot
 bit 1    do not notify users
 bit 2    halt after shutdown
 bit 3    shutdown due to power fail (used by UPS)
 bits 4-7    reserved
 bits 8-14    user definable
 bit 15 reserved
--------N-215FC9-----------------------------
INT 21 - LANtastic v4.0+ - CANCEL SERVER SHUTDOWN
    AX = 5FC9h
    ES:DI -> ASCIZ server name in form "\\machine"
Return: CF clear if successful
    CF set on error
        AX = error code
Note:    you must have the "S" privilege to use this call
SeeAlso: AX=5FC8h
--------N-215FCA-----------------------------
INT 21 - LANtastic v4.0+ - STUFF SERVER KEYBOARD BUFFER
    AX = 5FCAh
    ES:DI -> ASCIZ server name in form "\\machine"
    DS:SI -> ASCIZ string to stuff (128 bytes)
Return: CF clear if successful
    CF set on error
        AX = error code
Note:    you must have the "S" privilege to use this call
    maximum number of characters that can be stuffed is determined by the
      server's RUN BUFFER SIZE.
SeeAlso: INT 16/AH=05h
--------N-215FCB-----------------------------
INT 21 - LANtastic v4.1+ - TERMINATE USER
    AX = 5FCBh
    ES:DI -> ASCIZ server name in form "\\machine"
    DS:SI -> blank-padded username.     A null char = wildcard.
    DS:DX -> blank-padded machine name.  A null char = wildcard.
    CX = minutes until termination (0 = immediate)
Return: CF clear if successful
    CF set on error
        AX = error code
Note:    you must have the "S" privilege to use this call
    you cannot log yourself out using this call
SeeAlso: AX=5F82h
--------N-215FCC-----------------------------
INT 21 - LANtastic v4.1+ - GET/SET SERVER CONTROL BITS
    AX = 5FCCh
    ES:DI -> ASCIZ server name in form "\\machine"
    CX = bit values (value of bits you want to set) (see below)
    DX = bit mask (bits you are interested in, 0 = get only) (see below)
Return: CF clear if successful
        CX = control bits after call
        bit 0: disable logins
    CF set on error
        AX = error code
Note:    you must have the "S" privilege to SET, anyone can GET.
--------N-215FCD-----------------------------
INT 21 - LANtastic v4.1+ - FLUSH SERVER CACHES
    AX = 5FCDh
    ES:DI -> ASCIZ server name in form "\\machine"
Return: CF clear if successful
    CF set on error
        AX = error code
Note:    you must have the "S" privilege to use this call.
--------N-215FD0-----------------------------
INT 21 - LANtastic - GET REDIRECTED PRINTER TIMEOUT
    AX = 5FD0h
Return: CF clear if successful
        CX = redirected printer timeout in clock ticks of 55ms
        0000h if timeout disabled
    CF set on error
        AX = error code
SeeAlso: AX=5FD1h
--------N-215FD1-----------------------------
INT 21 - LANtastic - SET REDIRECTED PRINTER TIMEOUT
    AX = 5FD1h
    CX = printer timeout in clock ticks of 55ms, 0000h to disable timeouts
Return: CF clear if successful
    CF set on error
        AX = error code
SeeAlso: AX=5FD0h
--------N-215FE0-----------------------------
INT 21 C - LANtastic - GET DOS SERVICE VECTOR
    AX = 5FE0h
Return: CF clear if successful
        ES:BX -> current FAR service routine
    CF set on error
        AX = error code
Note:    the service routine is called by the LANtastic redirector whenever DOS
      may safely be called, permitting external TSRs and drivers to hook
      into LANtastic's DOS busy flag checking
SeeAlso: AX=5FE1h,INT 28,INT 2A/AH=84h
--------N-215FE1-----------------------------
INT 21 - LANtastic - SET DOS SERVICE VECTOR
    AX = 5FE1h
    ES:BX -> FAR routine to call when DOS services are available
Return: CF clear if successful
    CF set on error
        AX = error code
Note:    new handler must chain to previous handler as its first action
SeeAlso: AX=5FE0h
--------N-215FE2-----------------------------
INT 21 - LANtastic - GET MESSAGE SERVICE VECTOR
    AX = 5FE2h
Return: CF clear if successful
        ES:BX -> current FAR message service routine
    CF set on error
        AX = error code
SeeAlso: AX=5FE0h,AX=5FE3h
--------N-215FE3-----------------------------
INT 21 - LANtastic - SET MESSAGE SERVICE VECTOR
    AX = 5FE3h
    ES:BX -> FAR routine for processing network messages
Return: CF clear if successful
    CF set on error
        AX = error code
Notes:    handler must chain to previous handler as its first action
    on invocation, ES:BX -> just-received message
SeeAlso: AX=5FE2h
--------D-2160-------------------------------
INT 21 - DOS 3.0+ - "TRUENAME" - CANONICALIZE FILENAME OR PATH
    AH = 60h
    DS:SI -> ASCIZ filename or path
    ES:DI -> 128-byte buffer for canonicalized name
Return: CF set on error
        AX = error code
        02h invalid component in directory path or drive letter only
        03h malformed path or invalid drive letter
        ES:DI buffer unchanged
    CF clear if successful
        AH = 00h
        AL = destroyed (00h or 5Ch or last char of current dir on drive)
        buffer filled with qualified name of form D:\PATH\FILE.EXT or
          \\MACHINE\PATH\FILE.EXT
Desc:    determine the canonical name of the specified filename or path,
      corresponding to the undocumented TRUENAME command in COMMAND.COM
Notes:    the input path need not actually exist
    letters are uppercased, forward slashes converted to backslashes,
      asterisks converted to appropriate number of question marks, and
      file and directory names are truncated to 8.3 if necessary.  (DR-DOS
      3.41 and 5.0 do not expand asterisks)
    '.' and '..' in the path are resolved
    filespecs on local drives always start with "d:", those on network
      drives always start with "\\"
    if path string is on a JOINed drive, the returned name is the one that
      would be needed if the drive were not JOINed; similarly for a
      SUBSTed, ASSIGNed, or network drive letter.    Because of this, it is
      possible to get a qualified name that is not legal under the current
      combination of SUBSTs, ASSIGNs, JOINs, and network redirections
    under DOS 3.3 through 6.00, a device name is translated differently if
      the device name does not have an explicit directory or the directory
      is \DEV (relative directory DEV from the root directory works
      correctly).  In these cases, the returned string consists of the
      unchanged device name and extension appended to the string X:/
      (forward slash instead of backward slash as in all other cases) where
      X is the default or explicit drive letter.
    functions which take pathnames require canonical paths if invoked via
      INT 21/AX=5D00h
    supported by OS/2 v1.1 compatibility box
    NetWare 2.1x does not support characters with the high bit set; early
      versions of NetWare 386 support such characters except in this call.
      In addition, NetWare returns error code 3 for the path "X:\"; one
      should use "X:\." instead.
    for DOS 3.3-6.0, the input and output buffers may be the same, as the
      canonicalized name is built in an internal buffer and copied to the
      specified output buffer as the very last step
    for DR DOS 6.0, this function is not automatically called when on a
      network.  Device drivers reportedly cannot make this call from their
      INIT function.  Using the same pointer for both input and output
      buffers is not supported in the April 1992 and earlier versions of
      DR DOS
SeeAlso: AX=5FB3h,INT 2F/AX=1123h,INT 2F/AX=1221h
--------D-2161-------------------------------
INT 21 - DOS 3+ - UNUSED
    AH = 61h
Return: AL = 00h
Note:    this function does nothing and returns immediately
--------O-2161--BP6467-----------------------
INT 21 U - OS/2 v1.x FAPI - OS/2 FILE SYSTEM JOIN/SUBST
    AH = 61h
    BP = 6467h ("dg")
    AL = function
        00h list
        01h add
        02h delete
    BX = drive number
    CX = size of buffer
    SI = type (0002h JOIN, 0003h SUBST)
    ES:DI -> buffer
Return: ???
Notes:    used by JOIN and SUBST to communicate with the OS/2 file system
    also supported by OS/2 v2.0+ Virtual DOS Machines
--------D-2162-------------------------------
INT 21 - DOS 3+ - GET CURRENT PSP ADDRESS
    AH = 62h
Return: BX = segment of PSP for current process
Notes:    under DOS 3+, this function does not use any of the DOS-internal stacks
      and may thus be called at any time, even during another INT 21h call
    the current PSP is not necessarily the caller's PSP
    identical to the undocumented AH=51h
SeeAlso: AH=50h,AH=51h
--------D-216300-----------------------------
INT 21 - DOS 2.25 only - GET LEAD BYTE TABLE ADDRESS
    AX = 6300h
Return: CF clear if successful
        DS:SI -> lead byte table (see below)
    CF set on error
        AX = error code (01h) (see AH=59h)
Notes:    does not preserve any registers other than SS:SP
    the US version of MS-DOS 3.30 treats this as an unused function,
      setting AL=00h and returning immediately
SeeAlso: AX=6301h,AH=07h,AH=08h,AH=0Bh

Format of lead byte table entry:
Offset    Size    Description
 00h  2 BYTEs    low/high ends of a range of leading byte of double-byte chars
 02h  2 BYTEs    low/high ends of a range of leading byte of double-byte chars
    ...
  N   2 BYTEs    00h,00h end flag
--------D-216300-----------------------------
INT 21 - Far East DOS 3.2+ - GET DOUBLE BYTE CHARACTER SET LEAD-BYTE TABLE
    AX = 6300h
Return: AL = error code
        00h successful
        DS:SI -> DBCS table (see below)
        all other registers except CS:IP and SS:SP destroyed
        FFh not supported
Notes:    probably identical to AH=63h/AL=00h for DOS 2.25
    the US version of MS-DOS 3.30 treats this as an unused function,
      setting AL=00h and returning immediately
    the US version of DOS 4.0+ accepts this function, but returns an empty
      list
SeeAlso: AX=6300h"DOS 2.25"

Format of DBCS table:
Offset    Size    Description
 00h  2 BYTEs    low/high ends of a range of leading byte of double-byte chars
 02h  2 BYTEs    low/high ends of a range of leading byte of double-byte chars
    ...
  N   2 BYTEs    00h,00h end flag
--------D-216301-----------------------------
INT 21 - DOS 2.25, Far East DOS 3.2+ - SET KOREAN (HANGEUL) INPUT MODE
    AX = 6301h
    DL = new mode
        00h return only full characters on DOS keyboard input functions
        01h return partially-formed (interim) characters also
Return: AL = status
        00h successful
        FFh invalid mode
SeeAlso: AH=07h,AH=08h,AH=0Bh,AH=63h,AX=6302h
--------D-216302-----------------------------
INT 21 - DOS 2.25, Far East DOS 3.2+ - GET KOREAN (HANGEUL) INPUT MODE
    AX = 6302h
Return: AL = status
        00h successful
        DL = current input mode
            00h return only full characters (clears interim flag)
            01h return partial characters (sets interim flag)
        FFh not supported
SeeAlso: AH=07h,AH=08h,AH=0Bh,AH=63h,AX=6301h
--------D-2164-------------------------------
INT 21 - DOS 3.2+ internal - SET DEVICE DRIVER LOOKAHEAD FLAG
    AH = 64h
    AL = flag
        00h (default) call device driver function 5 (non-dest read)
            before INT 21/AH=01h,08h,0Ah
        nonzero don't call driver function 5
Return: nothing (MS-DOS)
    CF set, AX=error code??? (DR-DOS 5.0, which does not support this call)
Notes:    called by DOS 3.3+ PRINT.COM
    under MS-DOS, this function does not use any of the DOS-internal stacks
      and may thus be called at any time, even during another DOS call
SeeAlso: AH=01h,AH=08h,AH=0Ah,AX=5D06h
--------O-2164--DX0000-----------------------
INT 21 U - OS/2 v2.0+ Virtual DOS Machine - ENABLE AUTOMATIC TITLE SWITCH
    AH = 64h
    DX = 0000h (function number)
    CX = 636Ch (magic value, "cl")
    BX = 0000h (indicates special request)
Note:    if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
      in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
SeeAlso: AH=64h/BX=0001h,INT 21/AH=4Bh
--------O-2164--DX0001-----------------------
INT 21 U - OS/2 v2.0+ Virtual DOS Machine - SET SESSION TITLE
    AH = 64h
    DX = 0001h (function number)
    CX = 636Ch (magic value, "cl")
    BX = 0000h (indicates special request)
    ES:DI -> new ASCIZ title (max 12 char) or "" to restore default title
Note:    if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
      in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
SeeAlso: AH=64h/BX=0000h,AH=64h/BX=0002h,INT 15/AH=12h/BH=05h
--------O-2164--DX0002-----------------------
INT 21 U - OS/2 v2.0+ Virtual DOS Machine - GET SESSION TITLE
    AH = 64h
    DX = 0002h (function number)
    CX = 636Ch (magic value, "cl")
    BX = 0000h (indicates special request)
    ES:DI -> 13-byte buffer for current title
Return: buffer filled (single 00h if title never changed)
Note:    if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
      in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
SeeAlso: AH=64h/BX=0000h,AH=64h/BX=0001h,INT 15/AH=12h/BH=05h
--------O-2164--DX0003-----------------------
INT 21 U - OS/2 v2.1+ Virtual DOS Machine - GET LASTDRIVE
    AH = 64h
    DX = 0003h (function number)
    CX = 636Ch (magic value, "cl")
    BX = 0000h (indicates special request)
Return: AL = highest drive supported
Notes:    if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
      in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
    used by WinOS2
--------O-2164--DX0004-----------------------
INT 21 U - OS/2 v2.1+ Virtual DOS Machine - GET SIZE OF PTDA JFT
    AH = 64h
    DX = 0004h (function number)
    CX = 636Ch (magic value, "cl")
    BX = 0000h (indicates special request)
Return: AX = number of entries in OS/2 JFT for VDM
Notes:    if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
      in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
    in an OS/2 VDM, the DOS Job File Table in the PSP contains an index
      into the OS/2 JFT in the Per-Task Data Area rather than an SFT index
      because the OS/2 SFT can contain more than 255 entries
--------O-2164--DX0005-----------------------
INT 21 U - OS/2 v2.1+ Virtual DOS Machine - GET SECOND SFT FLAGS WORD
    AH = 64h
    DX = 0005h (function number)
    CX = 636Ch (magic value, "cl")
    BX = 0000h (indicates special request)
    DI = DOS file handle
Return: AX = value of second flags word from OS/2 SFT entry for file
Notes:    if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
      in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
    the OS/2 SFT has two flags words rather than DOS's one word, and this
      function provides access to the word which is not present in DOS
--------O-2164--DX0006-----------------------
INT 21 U - OS/2 v2.1+ Virtual DOS Machine - UNLOAD DOSKRNL SYMBOLS & LOAD PROGR
    AH = 64h
    DX = 0006h (function number)
    CX = 636Ch (magic value, "cl")
    BX = 0000h (indicates special request)
    ES:DI -> ASCIZ filespec
    DS = base address for loading
Notes:    if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
      in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
    this function is only supported by the kernel debugging version of
      OS2KRNL
--------O-2164--DX0007-----------------------
INT 21 U - OS/2 v2.1+ Virtual DOS Machine - GET WinOS2 CALL GATE ADDRESS
    AH = 64h
    DX = 0007h (function number)
    CX = 636Ch (magic value, "cl")
    BX = 0000h (indicates special request)
Return: AX = call gate address
Notes:    if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
      in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
    used by WinOS2 to make direct calls to OS2KRNL, bypassing the overhead
      of DOSKRNL
--------O-2164--DX0008-----------------------
INT 21 U - OS/2 v2.1+ Virtual DOS Machine - GET LOADING MESSAGE
    AH = 64h
    DX = 0008h (function number)
    CX = 636Ch (magic value, "cl")
    BX = 0000h (indicates special request)
Return: DS:DX -> '$'-terminated message "Loading.  Please wait."
Notes:    if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
      in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
    this function permits National Language Support for the initial message
      displayed while WinOS2 starts a full-screen session
--------O-2164--CX636C-----------------------
INT 21 U - OS/2 v2.1+ Virtual DOS Machine - OS/2 API support
    AH = 64h
    CX = 636Ch ("cl")
    BX = API ordinal (see below)
    other registers as appropriate for API call
      if ordinal 0025h:
        DS:SI -> STARTDATA structure (see below)
Return: as appropriate for API call
      if ordinal 0025h:
        AX = return code

Values for API ordinal:
 0025h    DOS32StartSession
 0082h    DosGetCP
 00A7h    DosQFSAttach
 00BFh    DosEditName
 00CBh    DosForceDelete
 0144h    Dos32CreateEventSem
 0145h    Dos32OpenEvenSem
 0146h    Dos32CloseEventSem
 0147h    Dos32ResetEventSem
 0148h    Dos32PostEventSem
 0149h    Dos32WaitEventSem
 014Ah    Dos32QueryEventSem
 014Bh    Dos32CreateMutexSem
 014Ch    Dos32OpenMutexSem
 014Dh    Dos32CloseMutexSem
 014Eh    Dos32RequestMutexSem
 014Fh    Dos32ReleaseMutexSem
 0150h    Dos32QueryMutexSem
 0151h    Dos32CreateMuxWaitSem
 0152h    Dos32OpenMuxWaitSem
 0153h    Dos32CloseMuxWaitSem
 0154h    Dos32WaitMuxWaitSem
 0155h    Dos32AddMuxWaitSem
 0156h    Dos32DeleteMuxWaitSem
 0157h    Dos32QueryMuxWaitSem

Format of STARTDATA structure:
Offset    Size    Description
 00h    WORD    length of structure (must be 0018h,001Eh,0020h,0032h,or 003Ch)
 02h    WORD    relation of new process to caller (00h independent, 01h child)
 04h    WORD    fore/background (00h foreground, 01h background)
 06h    WORD    trace options (00h-02h, 00h = no trace)
 08h    DWORD    pointer to ASCIZ program title (max 62 chars) or 0000h:0000h
 0Ch    DWORD    pointer to ASCIZ program name (max 128 chars) or 0000h:0000h
 10h    DWORD    pointer to ASCIZ program args (max 144 chars) or 0000h:0000h
 14h    DWORD    "TermQ" (currently reserved, must be 00000000h)
 18h    DWORD    pointer to environment (max 486 bytes) or 0000h:0000h
 1Ch    WORD    inheritance (00h or 01h)
 1Eh    WORD    session type
        00h OS/2 session manager determines type (default)
        01h OS/2 full-screen
        02h OS/2 window
        03h PM
        04h VDM full-screen
        07h VDM window
 20h    DWORD    pointer to ASCIZ icon filename (max 128 chars) or 0000h:0000h
 24h    DWORD    "PgmHandle" (currently reserved, must be 00000000h)
 28h    WORD    "PgmControl"
 2Ah    WORD    initial column
 2Ch    WORD    initial row
 2Eh    WORD    initial width
 30h    WORD    initial height
 32h    WORD    reserved (0)
 34h    DWORD    "ObjectBuffer" (currently reserved, must be 00000000h)
 38h    DWORD    "ObjectBufferLen" (currently reserved, must be 00000000h)
--------D-2165-------------------------------
INT 21 - DOS 3.3+ - GET EXTENDED COUNTRY INFORMATION
    AH = 65h
    AL = info ID
        01h get general internationalization info
        02h get pointer to uppercase table
        04h get pointer to filename uppercase table
        05h get pointer to filename terminator table
        06h get pointer to collating sequence table
        07h (DOS 4+) get pointer to Double-Byte Character Set table
    BX = code page (FFFFh=global code page)
    DX = country ID (FFFFh=current country)
    ES:DI -> country information buffer (see below)
    CX = size of buffer (>= 5)
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        CX = size of country information returned
        ES:DI -> country information
Notes:    AL=05h appears to return same info for all countries and codepages; it
      has been documented for DOS 5+, but was undocumented in ealier
      versions
    NLSFUNC must be installed to get info for countries other than the
      default
    subfunctions 02h and 04h are identical under OS/2
SeeAlso: AH=38h,INT 2F/AX=1401h,INT 2F/AX=1402h,INT 2F/AX=14FEh

Format of country information:
Offset    Size    Description
 00h    BYTE    info ID
---if info ID = 01h---
 01h    WORD    size
 03h    WORD    country ID
 05h    WORD    code page
 07h 34 BYTEs    country-dependent info (see AH=38h)
---if info ID = 02h---
 01h    DWORD    pointer to uppercase table (see below)
---if info ID = 04h---
 01h    DWORD    pointer to filename uppercase table (see below)
---if info ID = 05h---
 01h    DWORD    pointer to filename character table (see below)
---if info ID = 06h---
 01h    DWORD    pointer to collating table (see below)
---if info ID = 07h (DOS 4+)---
 01h    DWORD    pointer to DBCS lead byte table (see below)

Format of uppercase table:
Offset    Size    Description
 00h    WORD    table size
 02h 128 BYTEs    uppercase equivalents (if any) of chars 80h to FFh

Format of collating table:
Offset    Size    Description
 00h    WORD    table size
 02h 256 BYTEs    values used to sort characters 00h to FFh

Format of filename terminator table:
Offset    Size    Description
 00h    WORD    table size (not counting this word)
 02h    BYTE    ??? (01h for MS-DOS 3.30-6.00)
 03h    BYTE    lowest permissible character value for filename
 04h    BYTE    highest permissible character value for filename
 05h    BYTE    ??? (00h for MS-DOS 3.30-6.00)
 06h    BYTE    first excluded character in range \ all characters in this
 07h    BYTE    last excluded character in range  / range are illegal
 08h    BYTE    ??? (02h for MS-DOS 3.30-6.00)
 09h    BYTE    number of illegal (terminator) characters
 0Ah  N BYTEs    characters which terminate a filename:    ."/\[]:|<>+=;,
Note:    partially documented for DOS 5+, but undocumented for earlier versions

Format of filename uppercase table:
Offset    Size    Description
 00h    WORD    table size
 02h 128 BYTEs    uppercase equivalents (if any) of chars 80h to FFh

Format of DBCS lead byte table:
Offset    Size    Description
 00h    WORD    length
 02h 2N BYTEs    start/end for N lead byte ranges
    WORD    0000h    (end of table)
--------D-2165-------------------------------
INT 21 - DOS 4+ - COUNTRY-DEPENDENT CHARACTER CAPITALIZATION
    AH = 65h
    AL = function
        20h capitalize character
        DL = character to capitalize
        Return: DL = capitalized character
        21h capitalize string
        DS:DX -> string to capitalize
        CX = length of string
        22h capitalize ASCIZ string
        DS:DX -> ASCIZ string to capitalize
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
Note:    these calls have been documented for DOS 5+, but were undocumented in
      DOS 4.x.
--------D-216523-----------------------------
INT 21 U - DOS 4+ internal - DETERMINE IF CHARACTER REPRESENTS YES/NO RESPONSE
    AX = 6523h
    DL = character
    DH = second character of double-byte character (if applicable)
Return: CF set on error
    CF clear if successful
        AX = type
        00h no
        01h yes
        02h neither yes nor no
--------D-2165-------------------------------
INT 21 U - DOS 4+ internal - COUNTRY-DEPENDENT FILENAME CAPITALIZATION
    AH = 65h
    AL = function
        A0h capitalize filename character
        DL = character to capitalize
        Return: DL = capitalized character
        A1h capitalize counted filename string
        DS:DX -> filename string to capitalize
        CX = length of string
        A2h capitalize ASCIZ filename
        DS:DX -> ASCIZ filename to capitalize
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
Note:    nonfunctional in DOS 4.00 through 6.00 due to a bug (the code sets a
      pointer depending on the high bit of AL, but doesn't clear the
      bit before branching by function number).
--------D-216601-----------------------------
INT 21 - DOS 3.3+ - GET GLOBAL CODE PAGE TABLE
    AX = 6601h
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        BX = active code page (see AX=6602h)
        DX = system code page
SeeAlso: AX=6602h
--------D-216602-----------------------------
INT 21 - DOS 3.3+ - SET GLOBAL CODE PAGE TABLE
    AX = 6602h
    BX = active code page (see below)
    DX = system code page (active page at boot time)
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
SeeAlso: AX=6601h,INT 2F/AX=14FFh

Values for code page:
 437    US
 850    Multilingual
 852    Slavic/Latin II (DOS 5+)
 857    Turkish
 860    Portugal
 861    Iceland
 863    Canada (French)
 865    Norway/Denmark
--------D-2167-------------------------------
INT 21 - DOS 3.3+ - SET HANDLE COUNT
    AH = 67h
    BX = size of new file handle table for process
Return: CF clear if successful
    CF set on error
        AX = error code (see AH=59h)
Desc:    adjust the size of the per-process open file table, thus raising or
      lowering the limit on the number of files the caller can open
      simultaneously
Notes:    if BX <= 20, no action is taken if the handle limit has not yet been
      increased, and the table is copied back into the PSP if the limit
      is currently > 20 handles
    for file handle tables of > 20 handles, DOS 3.30 never reuses the
      same memory block, even if the limit is being reduced; this can lead
      to memory fragmentation as a new block is allocated and the existing
      one freed
    only the first 20 handles are copied to child processes in DOS 3.3-6.0
    increasing the file handles here will not, in general, increase the
      number of files that can be opened using the runtime library of a
      high-level language such as C
BUGS:    the original release of DOS 3.30 allocates a full 64K for the handle
      table on requests for an even number of handles
    DR-DOS 3.41 and 5.0 will lose track of any open file handles beyond
      the portion of the JFT retained after the call; MS-DOS will indicate
      error 04h if any of the JFT entries to be removed are open
SeeAlso: AH=26h,AH=86h
--------D-2168-------------------------------
INT 21 - DOS 3.3+ - "FFLUSH" - COMMIT FILE
    AH = 68h
    BX = file handle
Return: CF clear if successful
        all data still in DOS disk buffers is written to disk immediately,
          and the file's directory entry is updated
    CF set on error
        AX = error code (see AH=59h)
SeeAlso: AX=5D01h,AH=6Ah,INT 2F/AX=1107h
--------D-2169-------------------------------
INT 21 U - DOS 4+ internal - GET/SET DISK SERIAL NUMBER
    AH = 69h
    AL = subfunction
        00h get serial number
        01h set serial number
    BL = drive (0=default, 1=A, 2=B, etc)
    DS:DX -> disk info (see below)
Return: CF set on error
        AX = error code (see AH=59h)
    CF clear if successful
        AX destroyed
        (AL = 00h) buffer filled with appropriate values from extended BPB
        (AL = 01h) extended BPB on disk set to values from buffer
Notes:    does not generate a critical error; all errors are returned in AX
    error 0005h given if no extended BPB on disk
    does not work on network drives (error 0001h)
    buffer after first two bytes is exact copy of bytes 27h thru 3Dh of
      extended BPB on disk
    this function is supported under Novell NetWare versions 2.0A through
      3.11; the returned serial number is the one a DIR would display,
      the volume label is the NetWare volume label, and the file system
      is set to "FAT16".
    the serial number is computed from the current date and time when the
      disk is created; the first part is the sum of the seconds/hundredths
      and month/day, the second part is the sum of the hours/minutes and
      year
    the volume label which is read or set is the one stored in the extended
      BPB on disks formatted with DOS 4.0+, rather than the special root
      directory entry used by the DIR command in COMMAND.COM (use AH=11h
      to find that volume label)
SeeAlso: AX=440Dh

Format of disk info:
Offset    Size    Description
 00h    WORD    info level (zero)
 02h    DWORD    disk serial number (binary)
 06h 11 BYTEs    volume label or "NO NAME    " if none present
 11h  8 BYTEs    (AL=00h only) filesystem type--string "FAT12   " or "FAT16   "
--------O-2169-------------------------------
INT 21 - DR-DOS 5.0 - NULL FUNCTION
    AH = 69h
Return: AL = 00h
SeeAlso: AH=18h
--------v-216969-----------------------------
INT 21 - VIRUS - "Rape-747" - INSTALLATION CHECK
    AX = 6969h
Return: AX = 0666h if resident
SeeAlso: AX=58CCh,AH=76h"VIRUS"
--------d-2169FFDX0000-----------------------
INT 21 U - CUBIT v4.00 - GET CUBIT INT 21 HANDLER
    AX = 69FFh
    DX = 0000h
    BX = CB00h (magic value)
Return: ES:BX -> CUBITR.EXE handler for INT 21
Note:    the installation check consists of testing that the first eight bytes
      at the returned interrupt handler are EBh 07h "CUBITR" (a short
      jump around the signature followed by the signature); the byte
      following the signature (i.e. ES:[BX+8]) indicates whether CUBITR
      is active (01h) or disabled (00h)
SeeAlso: AX=69FFh/DX=CFBFh
Index:    installation check;CUBIT
--------d-2169FFDXCFBF-----------------------
INT 21 U - CUBIT v4.00 - UNINSTALL
    AX = 69FFh
    DX = CFBFh
    CX = EFCFh
    BX = CB00h (magic value)
Return: ES:BX -> CUBITR.EXE handler for INT 21
    CX = status
        2020h successful
        2222h failed
Note:    if DX is neither 0000h nor CFBFh on entry, some other code is executed
SeeAlso: AX=69FFh/DX=0000h
--------D-216A-------------------------------
INT 21 U - DOS 4+ - COMMIT FILE
    AH = 6Ah
    BX = file handle
Return: CF clear if successful
        AH = 68h
    CF set on error
        AX = error code (06h) (see AH=59h)
Note:    identical to AH=68h in DOS 5.0-6.0; not known whether this is the case
      in DOS 4.x
SeeAlso: AH=68h
--------D-216B-------------------------------
INT 21 U - DOS 4.0 internal - IFS IOCTL
    AH = 6Bh
    AL = subfunction
        00h ???
        DS:SI -> Current Directory Structure???
        CL = drive (1=A:)
        01h ???
        DS:SI -> ???
        CL = file handle???
        02h ???
        DS:SI -> Current Directory Structure???
        DI = ???
        CX = drive (1=A:)
Return: CF set on error
        AX = error code (see INT 21/AH=59h)
    CF clear if successful
Note:    passed through to INT 2F/AX=112Fh with AX on top of stack
SeeAlso: AH=6Bh"DOS 5",INT 2F/AX=112Fh
--------D-216B-------------------------------
INT 21 U - DOS 5+ - NULL FUNCTION
    AH = 6Bh
Return: AL = 00h
Note:    this function does nothing and returns immediately
SeeAlso: AH=6Bh"DOS 4"
--------D-216C00-----------------------------
INT 21 - DOS 4+ - EXTENDED OPEN/CREATE
    AX = 6C00h
    BL = open mode as in AL for normal open (see INT 21/AH=3Dh)
        bit 7: inheritance
        bits 4-6: sharing mode
        bit 3 reserved
        bits 0-2: access mode
    BH = flags
        bit 6 = auto commit on every write (see also AH=68h)
        bit 5 = return error rather than doing INT 24h
    CX = create attribute
        bits 6-15 reserved
        bit 5: archive
        bit 4: reserved
        bit 3: volume label
        bit 2: system
        bit 1: hidden
        bit 0: readonly
    DL = action if file exists/does not exists
        bits 7-4 action if file does not exist
            0000 fail
            0001 create
        bits 3-0 action if file exists
            0000 fail
            0001 open
            0010 replace/open
    DH = 00h (reserved)
    DS:SI -> ASCIZ file name
Return: CF set on error
       AX = error code (see AH=59h)
    CF clear if successful
       AX = file handle
       CX = status
        1 file opened
        2 file created
        3 file replaced
Note:    the PC LAN Program only supports DL=01h, DL=10h/sharing=compatibility,
      and DL=12h
SeeAlso: AH=3Ch,AH=3Dh,AX=6C01h
--------O-216C01-----------------------------
INT 21 U - OS/2 v2.0 - "DosOpen2"
    AX = 6C01h
    ???
Return: ???
Note:    this function is similar to AX=6C00h, but supports OS/2's extended
      attributes
SeeAlso: AX=5704h,AX=6C00h,AH=6Fh"OS/2"
--------D-216D-------------------------------
INT 21 U - DOS 5+ ROM - FIND FIRST ROM PROGRAM
    AH = 6Dh
    DS:DX -> ASCIZ program name
Return: CF clear if found
        [DTA] = ASCIZ name found
    CF set if not found
SeeAlso: AH=6Eh,AH=6Fh
--------O-216D-------------------------------
INT 21 U - OS/2 v1.x FAPI - "DosMkDir2"
    AH = 6Dh
    ???
Return: ???
Note:    also supported by OS/2 v2.0+ Virtual DOS Machines
SeeAlso: AH=39h
--------D-216E-------------------------------
INT 21 U - DOS 5+ ROM - FIND NEXT ROM PROGRAM
    AH = 6Eh
    [DTA] = result of previous FindFirst ROM
Return: CF clear if found
        [DTA] = ASCIZ name found
    CF set if not found
SeeAlso: AH=6Dh
--------O-216E-------------------------------
INT 21 U - OS/2 v1.x FAPI - "DosENumAttrib"
    AH = 6Eh
    ???
Return: ???
Note:    also supported by OS/2 v2.0+ Virtual DOS Machines
SeeAlso: AX=5703h,AH=6Fh"OS/2",INT 2F/AX=112Dh
--------O-216F-------------------------------
INT 21 U - OS/2 v1.x FAPI - "DosQMaxEASize" - GET MAXIMUM SIZE OF EXTENDED ATTR
    AH = 6Fh
    ???
Return: ???
Note:    also supported by OS/2 v2.0+ Virtual DOS Machines
SeeAlso: AX=5703h,AX=6C01h,AH=6Eh"OS/2"
--------D-216F00-----------------------------
INT 21 U - DOS 5+ ROM - GET ROM SCAN START ADDRESS
    AX = 6F00h
Return: BX = current ROM scan starting segment
SeeAlso: AH=6Dh,AX=6F01h,AX=6F02h
----------216F01-----------------------------
INT 21 U - DOS 5+ ROM - SET ROM SCAN START ADDRESS
    AX = 6F01h
    BX = new ROM scan starting address
SeeAlso: AX=6F00h,AX=6F03h
----------216F02-----------------------------
INT 21 U - DOS 5+ ROM - GET EXCLUSION REGION LIST
    AX = 6F02h
    ES:BX -> buffer for exclusion region list (see below)
Return: ES:BX = 0000h:0000h on error, unchanged if buffer filled
SeeAlso: AX=6F00h,AX=6F03h

Format of exclusion region list:
Offset    Size    Description
 00h    WORD    number of entries
 02h 2N WORDs    start/end segments of N excluded regions
----------216F03-----------------------------
INT 21 U - DOS 5+ ROM - SET EXCLUSION REGION LIST
    AX = 6F03h
    DS:DX -> new exclusion region list (see AX=6F02h)
Note:    DOS saves only the pointer and assumes that the contents of the list
      are never changed, and that regions do not overlap
SeeAlso: AX=6F01h,AX=6F02h
----------217070BX6060-----------------------
INT 21 - PCW Weather Card interface - GET DATA SEGMENT
    AX = 7070h
    BX = 6060h
    CX = 7070h
    DX = 7070h
    SI = 7070h
    DI = 7070h
Return: AX = segment of data structure
Notes:    the data structure is at offset 516 from this segment.
    the update byte is at offset 514 from this segment.  Updates are
      once per second while this byte is nonzero and it is decremented
      once per second.  While this byte is 0 updates are once per minute.
SeeAlso: AX=7070h/BX=7070h

Format of data structure:
Offset    Type    Description
 00h    WORD    hour
 02h    WORD    minute
 04h    WORD    second
 06h    WORD    day
 08h    WORD    month
 0Ah    WORD    year
 0Ch    WORD    ???
 0Eh    WORD    relative barometric pressure (in 1/100 inches)
 10h    WORD    ???
 12h    WORD    ???
 14h    WORD    temperature 1 (in 1/10 degrees F)
 16h    WORD    temperature 1 lowest (in 1/10 degrees F)
 18h    WORD    temperature 1 highest (in 1/10 degrees F)
 1Ah    WORD    temperature 2 (in 1/10 degrees F)
 1Ch    WORD    temperature 2 lowest (in 1/10 degrees F)
 1Eh    WORD    temperature 2 highest (in 1/10 degrees F)
 20h    WORD    wind speed (in MPH)
 22h    WORD    average of 60 wind speed samples (in MPH)
 24h    WORD    highest wind speed (in MPH)
 26h    WORD    wind chill factor  (in 1/10 degrees F)
 28h    WORD    lowest wind chill factor (in 1/10 degrees F)
 2Ah    WORD    ???
 2Ch    WORD    wind direction (in degrees)
 2Eh    WORD    accumulated daily rainfall (in 1/10 inches)
 30h    WORD    accumulated annual rainfall (in 1/10 inches)
----------217070BX7070-----------------------
INT 21 - PCW Weather Card interface - INSTALLATION CHECK
    AX = 7070h
    BX = 7070h
    CX = 7070h
    DX = 7070h
    SI = 7070h
    DI = 7070h
Return: AX = 0070h
    BX = 0070h
    CX = 0070h
    DX = 0070h
    SI = 0070h
    DI = 0070h
SeeAlso: AX=7070h/BX=6060h,AX=8080h
--------v-2176-------------------------------
INT 21 - VIRUS - "Klaeren"/"Hate" - INSTALLATION CHECK
    AH = 76h
Return: AL = 48h if resident
SeeAlso: AX=6969h,AX=7700h"VIRUS"
--------v-217700-----------------------------
INT 21 - VIRUS - "Growing Block" - INSTALLATION CHECK
    AX = 7700h
Return: AX = 0920h if resident
SeeAlso: AH=76h,AH=7Fh
----------217734-----------------------------
INT 21 U - SCROLLit v1.7 - INSTALLATION CHECK
    AX = 7734h
Return: DX = 3477h if installed
        AX = segment of resident code
Program: ScrollIt is a shareware backscroll utility by Bromfield Software
      Products
--------U-217761-----------------------------
INT 21 - WATCH.COM v3.2+ - INSTALLATION CHECK
    AX = 7761h ('wa')
Return: AX = 6177h
Note:    WATCH.COM is part of the "TSR" package by TurboPower Software
SeeAlso: INT 16/AX=7761h
--------v-217F-------------------------------
INT 21 - VIRUS - "Squeaker" - INSTALLATION CHECK
    AH = 7Fh
Return: AH = 80h if resident
SeeAlso: AX=7700h,AH=83h"VIRUS"
--------!------------------------------------