Oakland CPM Archive/oakcpm.iso/cpm/22rsx/rsx12.ark.2/RSXMAST.MAC

Text File | 1985-11-18 | 24.1 KB | 713 lines

    title    RSXMAST outline RSX for CPM2.2 (85/11/13)
;
; Copyright (c) 1985 by C.B Falconer       [phone]
; 680 Hartford Tpk, Hamden, Ct 06517.   All rights reserved.
;
; This program may be copied/used/modified etc, but it may NOT
; be sold without express written permission from C.B. Falconer
;
; This system was assembled with SLR's SLRMAC.  M80 can also be
; used, but care must be taken with macro parameter names.
;
rsxver    equ    12;    Version number to be filled in. <10 debug
;
; ==================== I M P O R T A N T =======================
; AN ACTUAL SYSTEM IS CONSTRUCTED WITH INCLUDE FILES.  THE FILES
; REQUIRED ARE:
;    RSXCUST.INC, RSXINIT.INC, BYERSX.INC and RSXMAIN.INC
; in addition to this file and BDOS.DEF
; If your assembler cannot handle include files, then you must
; make the insertions manually with your editor.
; ==============================================================
;
false    equ    0
true    equ    NOT false
no    equ    false;        synonyms for convenience
yes    equ    true
;
; The system implements a generalized CPM 2.2 RSX system.  The
; RSX is installed by running the system, and removed by running
; it again.  The program uses 8080 opcodes only in the RSX
; section, although the included files required may contain
; Z80 code.  This should ease porting to 8080 only systems.
;
; NOTE:    This source file requires SLRs SLRMAC or M80 for assembly,
;    and RELOCCP.SYS for run-time load and relocation.
;
; Revisions:        (in LIFO order)
; 1.2    85/11/13. FINDOS/CHKSYS are now application init callable
;    procs. BDOSLGH, BDOSARG, CCPLGH are now equates, to allow
;    for non-CPM systems.  Increased min. stack to 48 bytes.
;    Added boothk. Some name changes for M80 compatibility.
;    Modified the CCP re-entry mechanism for ZCPR compatibility.
; 1.1    85/11/09. Allowances for range of RSX's.  Drivers may now
;    be installed after a non-driver RSX has been mounted. These
;    changes allow implementation of a BYE replacement system.
;    Separate RSXCUST.INC file.
; 1.0    85/09/23. Initial release.
; 0.3    85/01/27. First working disk drive.
; 0.2    85/01/24. Provisions for BDOS driver installation,
;    checks etc.
; 0.1    85/01/05. Inactive causes reversion to original BDOS call in
;    case this was a substitute for it. debug allows testing.
;    Keep track of current DMA address.
; 0.0    Original version, by C.B. Falconer (85/Jan/04).
;
; This system is the outline of a generalized RSX system, with
; initialization and termination code.  It is expected to
; respond to BDOS calls with the value @RSX (normally larger
; than any usual CPM call value), and receive an argument of
; some form in the (de) register.  Two special values of (de)
; are reserved (0 and -1).  In usual operation the (de) value
; is normally a pointer, which cannot take on either of these
; special values.  For character output RSXs (e.g. list output
; replacement) this prevents sending a nul or a rubout with all
; bits set.  Remember this is a full word parameter.
;
; 0 implies a residence inquiry, and should return a zero
; value if the system is not resident, (as will CPM 2.2 for any
; invalid calls), and non-zero if resident and activated.  This
; allows the initialization code to detect that the system is
; already mounted, and avoid multiple loading.  Similarly
; application programs can check that the RSX is available.  A
; zero value returned in (a) signifies the RSX is not available.
;
; The second special value is 0ffffh (i.e. -1), which
; signals the system to become inactive, so that the next
; warm boot will remove it entirely.
;
; A third special argument is 0001h.  This is optional, and is
; used to return a data address.  For DSKDRIVE in particular
; this is used to return a pointer to the memory resident
; drive configuration table (whose structure thus should not
; be altered in order to maintain compatibility with auxiliary
; software).  (DSKDRIVE actually returns this pointer for all
; DE arguments other than 0 or -1, but this should not be
; counted on.)
;
; This file implements an example RSX, and indicates where the
; code should be installed, and the calling conventions for other
; RSXs.  See the label "chkparms" to allow initialization
; parameters, and the label "rsx" to install the actual code.
; Note especially than any code located ahead of the label
; "@keep" is available only during initialization.  However
; the initialization section can call routines in the retained
; portion.  The "bthook" connector allows re-initialization on
; each "warm boot" or disk reset.  "boothk" is different, and is
; called on each warm boot, but not at disk reset.
;
; The system, when combined with "RELOCCP", loads itself just
; below the CCP, and keeps the CCP resident. (See RELOCCP.OVR,
; which is an assembly time option for RELOCCP, for a method
; of minimizing memory wastage for multiple RSX's).  If RSX.COM
; is executed while resident, it attempts to remove itself and
; reclaim memory.  If other systems have been loaded below RSX
; it will not be able to reclaim memory until those systems
; (probably further RSX's) have been removed.  The customizable
; routine "killhk" allows manipulation of a resident RSX.
;
; To create a custom RSX modify the files RSXINIT, RSXMAIN, RSXCUST
; and possibly BYERSX.xxx, rename them with the extensions ".INC"
; and .DEF as required, and re-assemble RSXMAST.  Give the resultant
; relocatable file the appropriate name, and create the MYRSX.COM
; with RELOCCP (See RELOCCP documentation).  When executed you now
; have available a new BDOS function, which executes whatever you put
; in.  IF YOUR BDOS/CCP is non-standard see BDOS.DEF file.
;
; Acknowledgement:  Some of the mechanisms used in this system
; have been taken from various public domain systems, especially
; those by Gary Novasielski and Bruce Ratoff.
;
; This system was created to ease installation of two operations:
; a generalized foreign disc driver, and a "CHAIN" mechanism
; whereby programs can load and execute arbitrary commands.  The
; pre-existing KEYS program can probably be converted to execute
; under this system, as can UNSPOOL40 (enhancement of Br. Ratoffs
; UNSPOL30).
;
; While some code economies could easily be made for any particular
; application, I feel that using one standard environment is much
; more important.  Thus the provisions for bios driver modification
; have been installed, with the complete check/restore system.  The
; disadvantage remains that custom code must be included in this
; source and assembled, rather than standing by itself.
;
; Definitions of BDOS functions.
include BDOS.DEF
;
; Put any customization equates here
include    RSXCUST.DEF
;
; Macro Definitions
;
; Force location counter zero modulo val
; with respect to "wrto" by filling with "fill" bytes
align    macro    val,wrto,fill
    local    here
here    equ    $ - wrto
    if    (here+val)/val*val-here-val
     if    nul fill
      ds    (here+val)/val*val-here
     else;;    SLRMAC specific coding.
      ds    (here+val)/val*val-here,fill
     endif
    endif
    endm
;
; ************************************************************
; * This is my standard page relocatable system. See RELOCCP *
; ************************************************************
;
    cseg;    system requires org 0 and org 100h modules
;        You may replace this with two "orgs" in two
;        different assemblies to get the overall system
;        for RELOCCP to prepare and relocate at run-time.
;
; This defines the first location of the relocated image.
; The portion from here to "@keep" is not retained after
; initialization.  The data here is used for relocation
@base:    jmp    intro;        Following is std relocation data
@size:    dw    segsiz;        size of segment to relocate
@memsz:    db    pages;        total memory use in pages
;
; Patch/alter this value to non-zero if the RSX may only be
; loaded in a virgin system.  This should be done if the system
; installs bios modifications that the BDOS can see.
chkflg:    db    driver;        Set non-zero for virgin system only
;
; This code gets everything started
intro:    lhld    bdos+1;        First so other calls work
    shld    gobdos+1;    Save the BDOS entry point
    lxi    d,signon
    call    tstr
    call    findos
    jnz    badsys;        Invalid system configuration
;    "    "
; Set up the connector to return to CCP on boots
    lxi    d,-ccplgh-7+3;    Form pointer to CCP re-entry
    dad    d
    shld    ccpret+1;    and save for future use
;    "    "
; Do application specific parameter checking
    call    chkparms;    Do any parameter checking needed
    jc    exeunt;        ..with help message on carry=fault
;    "    "
; Check for initial load, or re-entry
    lxi    d,0
    mvi    a,@RSX;
    call    DOS;        enquire whether loaded
    ora    a;        If loaded, then
    jnz    intro1;           bring it down
    call    rsxset;        else initialize.
;    "    "
; Now do the user customizable initialization
    call    init;        Customized portion
    jmp    bootrq;        ..bootrq, which sets connectors
;
; already loaded, bring it down
intro1:    call    killhk;        for systems that modify running RSX
    lxi    d,-1
    mvi    a,@RSX
    call    DOS;        tell it to come down on next boot
    jmp    boot;        which should kill it
;
; Setup the system.  First, check environment to see if
; BIOS vectors are accessible and reasonable.
; a,f,c,d,e,h,l
rsxset:    lhld    boot+1
    shld    boot0+1;    Save the BOOT vector
    if    nodrive
         inx    h
     mov    e,m;        save warm boot connector
     inx    h
     mov    d,m
     xchg
     shld    bsave
     lxi    h,bootrq;    and reconnect to our system
     xchg
     mov    m,d
     dcx    h
     mov    m,e
     ret
    else;        drivers to be available
     lda    boot;        Location BOOT should
     cpi    0c3h;        have a JMP instruction
     jnz    vecterr
     lhld    boot+1;        Location one points to
     xchg;             the table of bios jumps
     lhld    bdos+1;        This should point to BDOS
     lda    chkflg
     sta    kill+1;        Save for use at exit time. Unclean
     ora    a;         but want it user patchable (1 place)
     if    multidrv
      call    findos
     else;        NOT multidrv
      cnz    chksys;        Hook, prevent loading invalid system
     endif
     xchg;            bios pointer to hl
     mvi    c,nvects;    preserve z flag in here
     lxi    d,biosv
     push    d;        by default init our vector
     jnz    vecterr;    after push, to correct stack
     lxi    d,bsave;    which we move into
     xchg;            the code.
;     "    "
; Now copy the original vectors into our tables, while verifying
; that they are reasonable (i.e. start with CALL or JMP).  The
; CALLs allow for warmboots that call a ROM routine, with the
; stack identifying the actual system location.
rsxset1: mvi    a,nvects-n22vec
     cmp    c
     jnc    rsxset2;    stop checking after 2.2 types
     ldax    d
     xra    m;        another JMP?
     ani    0f1h;        allow Call or Jmp
     jnz    vecterr
rsxset2: ldax    d
     mov    m,a;        bsave[n,0]
     inx    d
     inx    h
     xthl
     inx    h
     ldax    d
     mov    m,a;        biosv[n,1]
     inx    h
     xthl
     mov    m,a;        bsave[n,1]
     inx    d
     inx    h
     ldax    d
     mov    m,a;        bsave[n,2]
     xthl
     mov    m,a;        biosv[n,2]
     inx    h;    biosv[n+1,0]
     xthl
     inx    h;    biosv[n+1,0]
     inx    d
     dcr    c;    n := n+1;
     jnz    rsxset1
     pop    h;        purge 2nd transfer address
; This was satisfactory, now if "driver" is TRUE, patch the
; BIOS drivers to point to the new copy (only the std CPM 2.2
; entries) so that new entries can be made locally.  The final
; exit mechanism will restore everything.
     lda    chkflg
     ora    a
     rz;            no bios patches needed
;     "    "
; Patch the original bios drivers, which have been checked
; for validity and a reasonable location, to point to the
; new bios table. Only called when "driver" is TRUE.  DO NOT
; PATCH the original warm/cold boot entries.
bpatch:     lhld    boot+1
     inx    h
     inx    h
     lxi    d,biosv
     mvi    c,n22vec-1;    count of 2.2 bios entries only
bpat1:     inx    h
     inx    d
     inx    d
     inx    d
     inx    h
     mov    m,e
     inx    h
     mov    m,d
     dcr    c
     jnz    bpat1;        more
     ret
;
; Check system is in usable state. (de) holds the bios pointer,
; and (hl) holds the bdos pointer.  If the values are not
; reasonable, return non-zero flag.  If successful returns hl
; a pointer to location 7 on the BDOS entry page (CPM 2.2).
; Modifications here can allow installation of multiple
; drivers.  This is safer as it stands.
; a,f,h,l
chksys:     call    findos;        worked before, must work now
     mov    a,e
     cpi    3
     rnz;            boot pointer should end in 3
     mov    a,d
     sub    h
     sui    BDOSLGH;    Z flag if correct page,
     ret;            else non-virgin BIOS pointer
;
vecterr:
     pop    d;        remove the extra pointer
    endif;        NOT nodrive
;    "    "
; Exit with invalid system message
badsys:    lxi    d,vcterrmsg
;    "    "
; exit with message de^
exeunt:    call    tstr
    jmp    boot;        try re-booting.
;
vcterrmsg:
    db    CR,LF,'Invalid system$'
;
; Find the actual location of BDOS by following the trail from
; the pointer in hl.  Return z flag and hl = pointer to location
; 7 of the base BDOS page if found, else nz flag.
; For this to function connectors must be of the form used in
; intercept below.  Scan for label "intercept:"
; Note that ENTRY IS IN THE MIDDLE, not the next instruction
; a,f,h,l
fndos1:    cpi    03eh;        (mvi a).  Check for intercept
    rnz;            not a connector, not found
    inx    h;        ignore operand for MVI A,--
    inx    h
    mov    a,m
    cpi    0b9h;        (cmp c)
    rnz;            not a connector
    inx    h
    mov    a,m
    ani    0e7h;        may be an intercept
    cpi    0c2h;        jz, jnz, jc, jnc are acceptable
    rnz;            not a connector
    inx    h
fndos2:    mov    a,m
fndos3:    inx    h;        load the JMP operand
    mov    h,m
    mov    l,a;        and continue up the chain
;    "    "
; Main entry point here
findos:    mov    a,m;        find the actual BDOS.   *** ENTRY <<<
    cpi    0c3h;        (jmp).  Code for CPM 2.2 only
    jnz    fndos1;        Not the real thing
fndos4:    inx    h
    mov    a,m
    cpi    BDOSARG MOD 256;    known value in CPM 2.2
    jnz    fndos3;        not end, continue up the chain
    inx    h
    mov    a,m
    adi    BDOSARG / 256;    allow for non-CPM systems
    cmp    h;        at end JMP is on same page (CPM2.2)
    dcx    h;        point back to start of arg
    jnz    fndos2;        else continue up the chain
    ret;    (z)        FOUND it.
;
; =============================================================
; ****    Custom portion of initialization code here       ****
; =============================================================
;
; The following code is used on initialization and then discarded.
; See "RSXINIT.xxx" for details.  It may call on all routines in
; the system.
include    RSXINIT.INC
;
; ------------------ End custom initialization area ----------------
;
    align    256,@base,0;    ensure page aligned
;
; *******************************************************
; * The code from here up is retained in memory after     *
; * initialization.  It may be used by the initializer    *
; * This code MUST start on a page boundary.        *
; *******************************************************
@keep:
;
; During operation, this location will point to intercept and will
; be jumped to by BDOS calls from location 5.  This organization
; depends on the fact that BDOS calls the bios directly (ignoring
; the pointer at location 1), except when needing a warm boot
; (e.g. after a disk error), when it uses the pointer at 1.
;
; This must be at the lowest location in the protected code segment.
bdosv:    jmp    intercept;    the bdos link
;
; This will normally contain no code, but can be used to create a
; system compatible with the existing BYE programs.
include    BYERSX.INC
;
    if    nodrive
bsave:     dw    $-$;        save original warm boot connector
    else;        NOT nodrive
; This area replaces the bios jump table, allowing intercepts.
; Any intercepts (usually console commands) are set up by the
; initializing code, which is discarded after execution. See
; comments on "nvects" above.  Normally these bios vectors will be
; accessed only by executing programs, and not by the BDOS unit.
; To insert drivers in the bios it is necessary to save the original
; bios pointers (for restoration when the RSX is removed) and
; install jumps to this revised table in the original table.  Note
; that the original table may contain a CALL for the warmboot vector,
; so that ROM based code can tell the CPM system size when called.
biosv:     REPT    nvects;;    biosv is the new warmboot connector
     jmp    $-$
     endm
;
; This table has two purposes - it allows connection to the original
; bios vectors destinations, and it saves all the values for
; restoration upon RSX exit.  Thus the custom initialization section
; can patch the real bios table to install new disk drivers, etc.
; Note that this can only work when this is the FIRST rsx installed.
; Further ones can only intercept user bios calls and BDOS calls.
; Provided that the bios table in effect on entry to this system
; does not hold any data areas, the restoration on RSX removal will
; be harmless.
bsave:     REPT    nvects;;    bsave is the old warmboot connector
     jmp    $-$
     endm
;
; An example showing how to refer to the "old" entries needed.
; Index 0 here is warmboot, not cold.  Similarly for "new" entries
;@home        equ    bsave+(7*3)
;@seldk        equ    bsave+(8*3)
;@setrk        equ    bsave+(9*3)
;@setsec    equ    bsave+(10*3)
;@setdma    equ    bsave+(11*3)
;@read        equ    bsave+(12*3)
;@write        equ    bsave+(13*3)
;@sectran    equ    bsave+(15*3)
    endif;        NOT nodrive
;
; This routine intercepts all BDOS calls.
; Note that the initial code sequence allows applications to
; find the actual BDOS, if necessary.  See SD88F6 for one use.
intercept:
    mvi    a,0ffh
    cmp    c
    jc    gobdos;        Never taken, but SD trackable
    mvi    a,@SYS;        Get function
    cmp    c
    jz    sysreq;        a reboot request
    mvi    a,@DMA
    cmp    c
    jz    dodma
    mvi    a,@LOG
    cmp    c
    jz    drvreset;    reset this drive also
    mvi    a,@RSX;        defined for this system
    cmp    c
    jz    inrange
    mvi    a,@RSXX;    check for a special extra
    cmp    c;         intercept (e.g. setuser for
    jz    inrange;     BYE replacement)
    mvi    a,@RSXY;    check for another special extra
    cmp    c;         intercept (e.g. chain for
    jz    inrange;     BYE replacement)
    mvi    a,@RSXLO-1
    cmp    c
    jnc    gobdos;        not in range
    mvi    a,@RSXHI
    cmp    c
    jc    gobdos;        not for us
; DO NOT optimize the above sequence.  It is intended to be
; trackable by utilities to list the RSX's active.  The series
; stops when the instruction is not "ld a,bytevalue".  The
; initial "ld a,0ffh" will not be counted by tracking utilities
; and the checks on @SYS and @DMA are always expected.  This
; organization allows a range of BDOS calls to be intercepted.
;    "    "
inrange:
    lxi    h,0;        intercepting, switch stacks
    dad    sp;         because application may not
    lxi    sp,lclstk;     allow sufficient room
    push    h;        save entry stack pointer
    call    doit;        This is an extension call
    xchg;            save return value
    pop    h;        restore entry stack
    sphl
    xchg;            return its result
    mov    a,l;        copy result to (a)
    mov    b,h;        so (ba)=(hl), like BDOS
    ret;            to the caller.
;
; Reset this drive also when application wants a drive reset
; Added to RSX system for disk drive application.
; This is also called on any warm-boots
drvreset:
    push    b
    call    bthook;        user customizable.
    pop    b
    jmp    gobdos
;
; Keep track of the current DMA address on general principles
dodma:    xchg
    shld    dmadr;        BDOS' view, not BIOS
    xchg
;    "    "
; Connects to the "real" BDOS routine
gobdos:    jmp    $-$;        Patched on entry
;
; The RSX (resident system extension).  Argument is de as usual,
; and the extension specified is (c).  Return value is put in hl.
; The stack is already set to the local stack, with the old
; stack pointer under the return from doit.
; a,f,b,c,d,e,h,l (allowed)
doit:    lhld    active;        set "enquiry" return value in (l)
    mov    a,l
    ora    a
    jz    gobdos;        inactive, use bdos call
    mov    a,c
    cpi    @RSX
    jnz    rsx;        not the master call, ignore parm
    mvi    h,0
    mov    a,e;        check for "loaded enquiry"
    ora    d
    rz;            signal active on enquiry
    mov    a,e
    ana    d
    inr    a
    jnz    rsx;        not "pulldown" request.
;    "    "
; Inactivate the RSX.  Next boot will try to recover the memory.
kill:    mvi    a,$-$;        patched with "chkflg" at init
    ora    a
    cnz    unpch;        Remove any bios alterations
    xra    a
    sta    active;        mark inactive
    mov    l,a;        return 0, pulldown accepted
    mov    h,a;        and we are now inactive.
    ret
;
unpch:    if    nodrive
     ret
    else;        NOT nodrive
; Remove any bios patches made on initialization, in case this is a
; driver being inactivated, and further RSX's are loaded beyond it.
; Thus a "kill" request will be logically executed, even though the
; memory is not reclaimed. However bios alterations via the pointer
; at 1 cannot be removed until a warm boot occurs (that pointer may
; be pointing to an RSX installed later).  Thus the table at biosv
; must be updated to point to the original bios entries
     lxi    d,bsave+3
     lhld    boot0+1
     inx    h
     inx    h
     inx    h;        start at the constat entry
     push    h
     lxi    h,biosv+3
     mvi    c,n22vec-1;    dont alter the warm boot entries
unpch1:     mov    b,l;        offset, depends on page alignment
     inx    d;        past opcode
     inx    h;        Ignore the opcode (dont change)
     mov    m,b;    biosv[n,1]  --> oldbios[n,0]
     inx    h
     xthl
     mov    b,h;        oldbios page
     inx    h
     ldax    d;        lsb
     mov    m,a;    oldbios[n,1]
     inx    d;        ^msb
     inx    h
     ldax    d;        msb
     mov    m,a;    oldbios[n,2]
     inx    h;    oldbios[n+1,0]
     xthl
     mov    m,b;    biosv[n,2] --> oldbios[n,0]
     inx    h;    biosv[n+1,0]
     inx    d;        next opcode
     dcr    c;    n := n+1
     jnz    unpch1
     pop    h
     ret
    endif;        NOT nodrive
;
; Note that the following "boot" entries will never be reached if a
; further RSX has been installed, since that RSX will intercept the
; boot and do a direct return to the CCP (unless it is inactive, and
; removes itself, when a whole chain of RSX removals can be started)
;
; The application process has requested a warm-boot by invoking BDOS
; function 0.  If the system is inactive remove it, otherwise return
; to the CCP via the stored (on initialization) CCP return value.
sysreq:    jmp    bootrq;        This allows separation if needed
;
; The application process has requested a reboot by jumping to
; location 0.  If we are no longer active, we will honor the request
; by executing the address found in the BOOT vector at entry.
; Otherwise return to CCP without rebooting.
bootrq:    lxi    sp,lclstk;    set up a valid stack
    lda    active
    ora    a
    jz    done;        Not active, all done. Remove self
    call    boothk;        For applications to detect reboot
    mvi    c,@LOG
    call    drvreset;    Reset drives, like any other reboot
    lxi    d,actmsg;     does.  Calls bthook routine
    call    tstr
    lxi    d,altid;    added message portion for
    call    tstr;          DSKDRIVE use
;    "    "
; Reset the system pointers to use this system.
    lxi    h,bdosv
    shld    bdos+1
    if    NOT nodrive;    else leave connectors alone
     lxi    h,bootrq
     shld    biosv+1
     lxi    h,biosv
     shld    boot+1
    endif;        NOT nodrive
    lxi    h,tbuff
    shld    dmadr;        Will be set by CCP
    lda    drvusr
    mov    c,a;        drive/user under which to re-enter
ccpret:    jmp    $-$;        Patched on startup
;
; Done with the system
done:    lxi    d,donemsg;    Message and jump to old boot addr.
    call    tstr;        as originally read from memory wd 1
    if    nodrive;    Then we have to reset the wboot
     lhld    bsave
     xchg
     lhld    boot0+1;    The original destination
     inx    h
     mov    m,e
     inx    h
     mov    m,d;        restore it all
    endif
boot0:    jmp    $-$;        Reboot. Patched on initialization
;                This value points to old bios table
;                and the old reboot resets connectors
;
; ================================================================
;          Utility routine area
; ================================================================
;
; Put string (de) to console, '$' terminated
; a,f
tstr:    mvi    a,@MSG
;    "    "
; dos call (a) without disturbing registers.  Does not use the RSX
; a,f
DOS:    push    b
    push    d
    push    h
    mov    c,a
    call    gobdos
    pop    h
    pop    d
    pop    b
    ret
;
; ==================================================================
; **** To keep as much as possible constant, put real RSX here    ****
; ==================================================================
;
; The following allows for machine dependant code for i/o drivers
; the file may consist of comments only if not needed.
include RSXIO.INC
;
; The following is the actual application code.  It may only call on
; the following routines: TSTR, DOS, GOBDOS. (See above)
include RSXMAIN.INC
;
; This organization allows RSXMAIN to assign storage contiguous
; to the local stack, but not past it.
    ds    STKSZ; Local stack of at least STKSZ/2 words
;            plus any remainder on page
    ds    2;    allow for dmadr below, forced to page end
; align to next page boundary
    align    256,bdosv
;
lclstk    equ    $-2;    Reserve space for following
dmadr    equ    lclstk;    Keeps track of current value known to DOS.
;            Note that this may not be that known to BIOS
;*************************************************
; End of segment to be relocated.
pages    equ    ($-@base)/256;    So loader knows memory needs.
;
    end
r