Int 21 Fn 3F  - Trusted Access - Nb.sys - Get State
 Int 21 Fn 40  - DOS 2+ - "write" - Write To File Or Device
 Int 21 Fn 40  - Turbo Debug Hardware Breakpoints - Send Cmd To Hardware Brkp
 Int 21 Fn 40  - PC/tcp Ipcust.sys - Write Configuration Data
 Int 21 Fn 40  U - Trusted Access - Nb.sys - Set State
 Int 21 Fn 4000  - Fartbell.exe - Installation Check
 Int 21 Fn 4001  - Fartbell.exe - Force Noise
 Int 21 Fn 41  - DOS 2+ - "unlink" - Delete File
 Int 21 Fn 4101  - Softlogic Data Guardian - ???
 Int 21  - DOS 2+ - "lseek" - Set Current File Position
 Int 21 Fn 4203  - Virus - "shake" - Installation Check
 Int 21 Fn 4243  - Virus - "invader" - Installation Check
 Int 21 Fn 4300  - DOS 2+ - Get File Attributes
 Int 21 Fn 4301  - DOS 2+ - "chmod" - Set File Attributes
 Int 21 Fn 4302  - Dr-dos 3.41+ Internal - Get Access Rights
 Int 21 Fn 4303  - Dr-dos 3.41+ Internal - Set Access Rights And Password
 Int 21 Fn 4304  U - Dr-dos 5.0-6.0 Internal - Get Encrypted Password
 Int 21 Fn 4305  U - Dr-dos 5.0-6.0 Internal - Set Extended File Attributes
 Int 21 Fn 4306  - Dr-dos 6.0 - Get File Owner
 Int 21 Fn 4307  - Dr-dos 6.0 - Set File Owner
 Int 21 Fn 4310  - Banyan Vines 2.1+ - Get Extended File Attributes
 Int 21 Fn 4311  - Banyan Vines 2.1+ - Set Extended File Attributes
 Int 21 Fn 4380  - Novell DOS 7 - Undelete Pending Delete File
 Int 21 Fn 4381  - Novell DOS 7 - Purge Pending Delete File
 Int 21 Fn 4400  - DOS 2+ - Ioctl - Get Device Information
 Int 21 Fn 4401  - DOS 2+ - Ioctl - Set Device Information
 Int 21 Fn 4402  - DOS 2+ - Ioctl - Read From Character Device Control Channe
 Int 21 Fn 4402  - Network Driver Interface Specification (ndis) 2.0.1 - Prot
 Int 21 Fn 4402  U - IBM System 36/38 Workstation Emulation - Vdi.sys - Get ?
 Int 21 Fn 4402  U - Lastbyte.sys V1.19 - Ioctl - Get ??? Table
 Int 21 Fn 4402  - Highumm.sys V1.17+ - Ioctl - Get API Address
 Int 21 Fn 4402  - Smartdrv.sys V3.x Only - Ioctl - Get Cache Status
 Int 21 Fn 4402  - Cd-rom Device Driver - Ioctl Input
 Int 21 Fn 4402  - Quarterdeck - QEMM-386 V5+ - Get API Entry Point
 Int 21 Fn 4402  U - Quarterdeck - Hookrom.sys - Get Hooked Vector Table
 Int 21 Fn 4402  - Advanced Scsi Programming Interface (aspi) - Interface
 Int 21 Fn 4402  U - Qualitas 386max V6.00+ - Ioctl Input - Get State
 Int 21 Fn 4402  U - Qualitas 386max V6.00+ - Ioctl Input - Get State  (Cont.)
 Int 21 Fn 4402  - Pgs1600.dev - Ioctl - Get Configuration Info
 Int 21 Fn 4402  - PC/tcp Ipcust.sys - Reset Configuration Data Read Pointer
 Int 21 Fn 4402  - Workgrp.sys - Get API Entry Point
 Int 21 Fn 4402  - 10net V5.0 - 10beui.dos - API
 Int 21 Fn 4402  - 10net V5.0 - 10memmgr.sys - API
 Int 21 Fn 4402  U - Memory Managers - Get API Entry Point
 Int 21 Fn 4402  U - Memory Managers - Get Emm Import Structure Address
 Int 21 Fn 4402  U - Memory Managers - Get Memory Manager Version
 Int 21 Fn 4402  U - Microsoft Emm386.exe V4.45 - Get Memory Manager Informat
 Int 21 Fn 4402  - Compaq Ag1024.sys - Rgdi - Get Driver Location
 Int 21 Fn 4402  - FTPsoft.dos V3.1 - Get ???
 Int 21 Fn 4402  U - Pendos Pendev.sys - Get Entry Points
 Int 21 Fn 4402  U - LAN Manager - Tcpdrv.dos - API
 Int 21 Fn 4402  U - PC Tools 9 Cprlow.exe - Get Code And Data Addresses
 Int 21 Fn 4403  - DOS 2+ - Ioctl - Write To Character Device Control Channel
 Int 21 Fn 4403  - Smartdrv.sys V3.x Only - Ioctl - Cache Control
 Int 21 Fn 4403  - Cd-rom Device Driver - Ioctl Output
 Int 21 Fn 4403  - Brian Antoine Seagate St-01 Scsi.sys - Ioctl - Execute Com
 Int 21 Fn 4403  U - Ai Architects - OS/x86??? - API
 Int 21 Fn 4403  - Pgs1600.dev - Ioctl - Set Configuration???
 Int 21 Fn 4403  - PC/tcp Ipcust.sys - Reset Configuration Data Read Pointer
 Int 21 Fn 4403  - Compaq Ag1024.sys - Cpq_mges - Ioctl Output
 Int 21 Fn 4403  - Compaq Ag1024.sys - Rgdi - Ioctl Output
 Int 21 Fn 4403  U - Qualitas 386max V6.01+ - Turn 386max Off
 Int 21 Fn 4403  U - Qualitas 386max V6.01+ - Turn 386max On
 Int 21 Fn 4403  U - Qualitas 386max V6.01+ - Set State
 Int 21 Fn 4403  U - Qualitas 386max V7.00+ - LIMit Automatic Activation To S
 Int 21 Fn 4403  U - Qualitas 386max V7.00+ - Allow Automatic Activation On A
 Int 21 Fn 4403  U - Pendos Pendev.sys - ???
 Int 21 Fn 4404  - DOS 2+ - Ioctl - Read From Block Device Control Channel
 Int 21 Fn 4404  - Stacker - Get Device Driver Address And Set Volume Number
 Int 21 Fn 4404  - Stacker - Get Stacvol File Sectors
 Int 21 Fn 4404  - Dubldisk.sys V2.6 - Get Info
 Int 21 Fn 4404  - Dblspace.bin - Ioctl - Flush Or Invalidate Internal Caches
 Int 21 Fn 4404  U - Xdisk V3.31 - Configure
 Int 21 Fn 4404  - Combi-disk V1.13 - Get Data Record
 Int 21 Fn 4405  - DOS 2+ - Ioctl - Write To Block Device Control Channel
 Int 21 Fn 4405  - Brian Antoine Seagate St-01 Scsi.sys - Ioctl - Execute Com
 Int 21 Fn 4405  U - Dblspace.bin - Ioctl - Flush Or Invalidate Internal Cach
 Int 21 Fn 4405  U - Xdisk V3.31 - ???
 Int 21 Fn 4405  - Combi-disk V1.13 - Control Combi-disk
 Int 21 Fn 4406  - DOS 2+ - Ioctl - Get Input Status
 Int 21 Fn 4407  - DOS 2+ - Ioctl - Get Output Status
 Int 21 Fn 4408  - DOS 3.0+ - Ioctl - Check If Block Device Removable
 Int 21 Fn 4409  - DOS 3.1+ - Ioctl - Check If Block Device Remote
 Int 21 Fn 440A  - DOS 3.1+ - Ioctl - Check If Handle Is Remote
 Int 21 Fn 440B  - DOS 3.1+ - Ioctl - Set Sharing Retry Count
 Int 21 Fn 440C  - DOS 3.2+ - Ioctl - Generic Character Device Request
 Int 21 Fn 440C  - Greg Shenaut Aspitape.sys - Interface
 Int 21 Fn 440D  - DOS 3.2+ - Ioctl - Generic Block Device Request
 Int 21 Fn 440E  - DOS 3.2+ - Ioctl - Get Logical Drive Map
 Int 21 Fn 440F  - DOS 3.2+ - Ioctl - Set Logical Drive Map
 Int 21 Fn 4410  - DOS 5+ - Ioctl - Query Generic Ioctl Capability (handle)
 Int 21 Fn 4410  U - Newspace - Enable Driver
 Int 21 Fn 4411  - DOS 5+ - Ioctl - Query Generic Ioctl Capability (drive)
 Int 21 Fn 4411  U - Newspace - Disable Driver
 Int 21 Fn 4412  - Dr-dos 5+ - Determine DOS Type
 Int 21 Fn 4412  U - Newspace - Installation Check???
 Int 21 Fn 4413  U - Newspace - Get ???
 Int 21 Fn 4414  U - Dr-dos 5.0 - Set Global Password
 Int 21 Fn 4414  U - Newspace - Debugging Dump
 Int 21 Fn 44  U - Dr-dos 5.0 - History Buffer, Share, And Hiload Control
 Int 21 Fn 4451  - Concurrent DOS V3.2+ - Installation Check
 Int 21 Fn 4452  - Dr-dos 3.41+ - Determine DOS Type/get Dr-dos Version
 Int 21 Fn 4454  U - Dr-dos 3.41+ - Set Global Password
 Int 21 Fn 4456  U - Dr-dos 5.0+ - History Buffer Control
 Int 21 Fn 4457  U - Dr-dos 5.0+ - Share/hiload Control
 Int 21 Fn 4457  U - Dr-dos 6.0 - Get Share Status
 Int 21 Fn 4458  U - Dr-dos 5.0+ Internal - Get Pointer To Internal Variable
 Int 21 Fn 4459  - Dr Multiuser DOS 5.0 - API
 Int 21 Fn 44E0  U - Sun PC-nfs - API???
 Int 21 Fn 44FF  U - Newspace - ???
 Int 21 Fn 45  - DOS 2+ - "dup" - Duplicate File Handle
 Int 21 Fn 46  - DOS 2+ - "dup2", "forcedup" - Force Duplicate File Handle
 Int 21 Fn 47  - DOS 2+ - "cwd" - Get Current Directory
 Int 21 Fn 48  - DOS 2+ - Allocate Memory
 Int 21 Fn 49  - DOS 2+ - Free Memory
 Int 21 Fn 4A  - DOS 2+ - Resize Memory Block
 Int 21 Fn 4B  - DOS 2+ - "exec" - Load And/or Execute Program
 Int 21 Fn 4B  - DOS 2+ - "exec" - Load And/or Execute Program  (Cont.)
 Int 21 Fn 4B  - DOS 2+ - "exec" - Load And/or Execute Program  (Cont.)
 Int 21 Fn 4B  - Elres V1.0 Only - Installation Check
 Int 21 Fn 4B04  - Virus - "mg", "699"/"thirteen Minutes" - Installation Chec
 Int 21 Fn 4B05  - DOS 5+ - Set Execution State
 Int 21 Fn 4B20  - Virus - "holocaust"/"telefonica" - ???
 Int 21 Fn 4B21  C - Virus - "holocaust"/"telefonica" - ???
 Int 21 Fn 4B25  - Virus - "1063"/"mono" - Installation Check
 Int 21 Fn 4B40  - Virus - "plastique"/"anticad" - Installation Check
 Int 21 Fn 4B41  - Virus - "plastique"/"anticad" - ???
 Int 21 Fn 4B4A  - Virus - "jabberwocky" - Installation Check
 Int 21 Fn 4B4B  - Virus - "horse-2" - Installation Check
 Int 21 Fn 4B4D  - Virus - "murphy-2", "patricia"/"smack" - Installation Chec
 Int 21 Fn 4B50  - Virus - "plastique-2576"/"anticad-2576" - Installation Che
 Int 21 Fn 4B53  - Virus - "horse" - Installation Check
 Int 21 Fn 4B55  - Virus - "sparse" - Installation Check
 Int 21 Fn 4B59  - Virus - "murphy-1", "murphy-4" - Installation Check
 Int 21 Fn 4B5E  - Virus - "brothers" - Installation Check
 Int 21 Fn 4B60  - Virus - "plastique-2576"/"anticad-2576" - ???
 Int 21 Fn 4B87  - Virus - "shirley" - Installation Check
 Int 21 Fn 4B95  - Virus - "zherkov-1882" - Installation Check
 Int 21 Fn 4BA7  - Virus - "1876"/"dash-em" - Installation Check
 Int 21 Fn 4BAA  - Virus - "nomenklatura" - Installation Check
 Int 21 Fn 4BAF  - Virus - "948"/"screenplus1", "magnitogorsk" - Installation
 Int 21 Fn 4BDD  - Virus - "lozinsky"/"zherkov" - Installation Check
 Int 21 Fn 4BEE  - F-driver.sys V1.14+ - Grab Int 21
 Int 21 Fn 4BF0  - Diet V1.10+ (overlay Mode) - Installation Check
 Int 21 Fn 4BF1  - Diet V1.10+ (overlay Mode) - Expand Program???
 Int 21 Fn 4BFE  - Virus - "hitchcock", "dark Avenger-1028", "1193" - Install
 Int 21 Fn 4BFF  - Virus - "ussr-707", "justice", "europe 92" - Installation
 Int 21 Fn 4BFF  - Virus - "cascade" - Installation Check
 Int 21 Fn 4C  - DOS 2+ - "exit" - Terminate With Return Code
 Int 21 Fn 4C57  - Headroom - ???
 Int 21 Fn 4D  - DOS 2+ - Get Return Code (errorlevel)
 Int 21 Fn 4E  - DOS 2+ - "findfirst" - Find First Matching File
 Int 21 Fn 4E  - Wildunix.com Internal - Installation Check
 Int 21 Fn 4F  - DOS 2+ - "findnext" - Find Next Matching File
 Int 21 Fn 50  - DOS 2+ Internal - Set Current Process Id (set Psp Address)
 Int 21 Fn 51  - DOS 2+ Internal - Get Current Process Id (get Psp Address)
 Int 21 Fn 52  U - DOS 2+ Internal - "sysvars" - Get List Of Lists
 Int 21 Fn 52  U - DOS 2+ Internal - "sysvars" - Get List Of Lists  (Cont.)
 Int 21 Fn 52  U - DOS 2+ Internal - "sysvars" - Get List Of Lists  (Cont.)
  4fh   word    offset In Current Directory Path Of Backslash Corresponding To
  4fh   word    offset In Current Directory Path Of Backslash Corresponding To  (Cont.)
 Int 21 Fn 5252  - Virus - "516"/"leapfrog" - Installation Check
 Int 21 Fn 53  - DOS 2+ Internal - Translate BIOS Parameter Block To Drive Pa
 Int 21 Fn 54  - DOS 2+ - Get Verify Flag
 Int 21 Fn 55  - DOS 2+ Internal - Create Child Psp
 Int 21 Fn 56  - DOS 2+ - "rename" - Rename File
 Int 21 Fn 5700  - DOS 2+ - Get File's Date And Time
 Int 21 Fn 5701  - DOS 2+ - Set File's Date And Time
 Int 21 Fn 5702  - DOS 4.x Only - Get Extended Attributes For File
 Int 21 Fn 5702  - OS/2 V1.1+ Family API - DOSqfileinfo
 Int 21 Fn 5702  - OS/2 V1.1+ Compatibility Box Family API - DOSqpathinfo
 Int 21 Fn 5703  - DOS 4.x Only - Get Extended Attribute Properties
 Int 21 Fn 5703  - OS/2 V1.1+ Family API - DOSsetfileinfo
 Int 21 Fn 5703  - OS/2 V1.1+ Family API - DOSsetpathinfo
 Int 21 Fn 5704  - DOS 4.x Only - Set Extended Attributes
 Int 21 Fn 5757  U - IBM Genie - Resident Manager - Installation Check
 Int 21 Fn 5758  U - Headroom - API
 Int 21 Fn 58  - DOS 3+ - Get Or Set Memory Allocation Strategy
 Int 21 Fn 58  - DOS 5+ - Get Or Set Umb Link State
 Int 21 Fn 58CC  - Virus - "1067"/"headcrash" - Installation Check
 Int 21 Fn 58DD  - Virus - "1067"/"headcrash" - Get Original Int 21h Vector
 Int 21 Fn 59  - DOS 3+ - Get Extended Error Information
 Int 21 Fn 59  - European MS-dos 4.0 - Get Hard Error Information
 Int 21 Fn 5A  - DOS 3+ - Create Temporary File
 Int 21 Fn 5B  - DOS 3+ - Create New File
 Int 21 Fn 5C  - DOS 3+ - "flock" - Record Locking
 Int 21 Fn 5D00  U - DOS 3.1+ Internal - Server Function Call
 Int 21 Fn 5D01  U - DOS 3.1+ Internal - Commit All Files For Specified Compu
 Int 21 Fn 5D02  U - DOS 3.1+ Internal - Share.exe - Close File By Name
 Int 21 Fn 5D03  U - DOS 3.1+ Internal - Share.exe - Close All Files For Give
 Int 21 Fn 5D04  U - DOS 3.1+ Internal - Share.exe - Close All Files For Give
 Int 21 Fn 5D05  U - DOS 3.1+ Internal - Share.exe - Get Open File List Entry
 Int 21 Fn 5D06  U - DOS 3.0+ Internal - Get Address Of Dos Swappable Data Ar
 Int 21 Fn 5D07  U - DOS 3.1+ Network - Get Redirected Printer Mode
 Int 21 Fn 5D08  U - DOS 3.1+ Network - Set Redirected Printer Mode
 Int 21 Fn 5D09  U - DOS 3.1+ Network - Flush Redirected Printer Output
 Int 21 Fn 5D0A  - DOS 3.1+ - Set Extended Error Information
 Int 21 Fn 5D0B  OU - DOS 4.x Only Internal - Get Dos Swappable Data Areas
 Int 21 Fn 5E00  - DOS 3.1+ Network - Get Machine Name
 Int 21 Fn 5E00  - 10net V5.0 - Get Machine Name
 Int 21 Fn 5E01  - DOS 3.1+ Network - Set Machine Name