Int 21  - Comtrol Hostess I/isa Debugger - Get Segment For Control Program U
 Int 21 Fn 00  - DOS 1+ - Terminate Program
 Int 21 Fn 01  - DOS 1+ - Read Character From Standard Input, With Echo
 Int 21 Fn 02  - DOS 1+ - Write Character To Standard Output
 Int 21 Fn 03  - DOS 1+ - Read Character From Stdaux
 Int 21 Fn 04  - DOS 1+ - Write Character To Stdaux
 Int 21 Fn 05  - DOS 1+ - Write Character To Printer
 Int 21 Fn 06  - DOS 1+ - Direct Console Output
 Int 21 Fn 06  - DOS 1+ - Direct Console Input
 Int 21 Fn 07  - DOS 1+ - Direct Character Input, Without Echo
 Int 21 Fn 08  - DOS 1+ - Character Input Without Echo
 Int 21 Fn 09  - DOS 1+ - Write String To Standard Output
 Int 21 Fn 0A  - DOS 1+ - Buffered Input
 Int 21 Fn 0A00  - Wced V1.6+ - Installation Check
 Int 21 Fn 0B  - DOS 1+ - Get Stdin Status
 Int 21 Fn 0B56  - Virus - "perfume" - Installation Check
 Int 21 Fn 0C  - DOS 1+ - Flush Buffer And Read Standard Input
 Int 21 Fn 0D  - DOS 1+ - Disk Reset
 Int 21 Fn 0D20  - Virus - "crazy Imp" - Installation Check
 Int 21 Fn 0E  - DOS 1+ - Select Default Drive
 Int 21 Fn 0F  - DOS 1+ - Open File Using Fcb
 Int 21 Fn 10  - DOS 1+ - Close File Using Fcb
 Int 21 Fn 11  - DOS 1+ - Find First Matching File Using Fcb
 Int 21 Fn 12  - DOS 1+ - Find Next Matching File Using Fcb
 Int 21 Fn 13  - DOS 1+ - Delete File Using Fcb
 Int 21 Fn 14  - DOS 1+ - Sequential Read From Fcb File
 Int 21 Fn 15  - DOS 1+ - Sequential Write To Fcb File
 Int 21 Fn 16  - DOS 1+ - Create Or Truncate File Using Fcb
 Int 21 Fn 17  - DOS 1+ - Rename File Using Fcb
 Int 21 Fn 18  - DOS 1+ - Null Function For Cp/m Compatibility
 Int 21 Fn 19  - DOS 1+ - Get Current Default Drive
 Int 21 Fn 1A  - DOS 1+ - Set Disk Transfer Area Address
 Int 21 Fn 1B  - DOS 1+ - Get Allocation Information For Default Drive
 Int 21 Fn 1C  - DOS 1+ - Get Allocation Information For Specific Drive
 Int 21 Fn 1D  - DOS 1+ - Null Function For Cp/m Compatibility
 Int 21 Fn 1E  - DOS 1+ - Null Function For Cp/m Compatibility
 Int 21 Fn 1F  - DOS 1+ - Get Drive Parameter Block For Default Drive
 Int 21 Fn 20  - DOS 1+ - Null Function For Cp/m Compatibility
 Int 21 Fn 21  - DOS 1+ - Read Random Record From Fcb File
 Int 21 Fn 22  - DOS 1+ - Write Random Record To Fcb File
 Int 21 Fn 23  - DOS 1+ - Get File Size For Fcb
 Int 21 Fn 24  - DOS 1+ - Set Random Record Number For Fcb
 Int 21 Fn 25  - DOS 1+ - Set Interrupt Vector
 Int 21 Fn 2501  P - Phar Lap 386/dos-extender - Reset DOS Extender Data Stru
 Int 21 Fn 2502  P - Phar Lap 386/dos-extender - Get Protected-mode Interrupt
 Int 21 Fn 2503  P - Phar Lap 386/dos-extender - Get Real-mode Interrupt Vect
 Int 21 Fn 2504  P - Phar Lap 386/dos-extender - Set Protected-mode Interrupt
 Int 21 Fn 2505  P - Phar Lap 386/dos-extender - Set Real-mode Interrupt Vect
 Int 21 Fn 2506  P - Phar Lap 386/dos-extender - Set Int To Always Gain Cntrl
 Int 21 Fn 2507  P - Phar Lap 386/dos-extender - Set Real- & Protected-mode I
 Int 21 Fn 2508  P - Phar Lap 386/dos-extender - Get Segment Linear Base Addr
 Int 21 Fn 2509  P - Phar Lap 386/dos-extender - Convert Linear To Physical A
 Int 21 Fn 2509  P - Flashtek X-32vm - Get System Segments And Selectors
 Int 21 Fn 250A  P - Phar Lap 386/dos-extender - Map Physical Memory At End O
 Int 21 Fn 250C  P - Phar Lap 386/dos-extender - Get Hardware Interrupt Vecto
 Int 21 Fn 250D  P - Phar Lap 386/dos-extender - Get Real-mode Link Informati
 Int 21 Fn 250E  P - Phar Lap 386/dos-extender - Call Real-mode Procedure
 Int 21 Fn 250F  P - Phar Lap 386/dos-extender - Convert Protected-mode Addre
 Int 21 Fn 2510  P - Phar Lap 386/dos-extender - Call Real-mode Procedure, Re
 Int 21 Fn 2511  P - Phar Lap 386/dos-extender - Issue Real-mode Interrupt
 Int 21 Fn 2512  P - Phar Lap 386/dos-extender - Load Program For Debugging
 Int 21 Fn 2513  P - Phar Lap 386/dos-extender - Alias Segment Descriptor
 Int 21 Fn 2514  P - Phar Lap 386/dos-extender - Change Segment Attributes
 Int 21 Fn 2515  P - Phar Lap 386/dos-extender - Get Segment Attributes
 Int 21 Fn 2516  P - Phar Lap 386/dos-extender V2.2+ - Free All Memory Owned
 Int 21 Fn 2517  P - Phar Lap 386/dos-extender V2.1c+ - Get Info On DOS Data
 Int 21 Fn 2518  P - Phar Lap 386/dos-extender 2.1c+ - Specify Handler For Mo
 Int 21 Fn 2519  P - Phar Lap 386/dos-extender Vmm - Get Additional Memory Er
 Int 21 Fn 251A  P - Phar Lap 386/dos-extender Vmm - Lock Pages In Memory
 Int 21 Fn 251B  P - Phar Lap 386/dos-extender Vmm - Unlock Pages
 Int 21 Fn 251C  P - Phar Lap 386/dos-extender Vmm V2.1c+ - Free Physical Mem
 Int 21 Fn 251D  OP - Phar Lap 386/dos-extender Vmm V2.1c - Read Page-table E
 Int 21 Fn 251E  OP - Phar Lap 386/dos-extender Vmm V2.1c - Write Page-table
 Int 21 Fn 251F  P - Phar Lap 386/dos-extender Vmm - Exhange Two Page-table E
 Int 21 Fn 2520  P - Phar Lap 386/dos-extender Vmm - Get Memory Statistics
 Int 21 Fn 2521  P - Phar Lap 386/dos-extender Vmm - LIMit Program's Extended
 Int 21 Fn 2522  P - Phar Lap 386/dos-ext Vmm V2.2+ - Specify Alternate Page-
 Int 21 Fn 2523  P - Phar Lap 386/dos-ext Vmm V2.2+ - Specify Out-of-swap-spa
 Int 21 Fn 2524  P - Phar Lap 386/dos-ext Vmm V2.2+ - Install Page-replacemen
 Int 21 Fn 2525  P - Phar Lap 386/dos-extender Vmm - LIMit Program's Convent'
 Int 21 Fn 2526  P - Phar Lap 386/dos-extender - Get Configuration Informatio
 Int 21 Fn 2527  P - Phar Lap 386/dos-extender Vmm - En/disable State Save On
 Int 21 Fn 2528  P - Phar Lap 386/dos-extender Vmm - Read Registers After Ctr
 Int 21 Fn 2529  P - Phar Lap 386/dos-extender - Load Flat Model .exp Or .rex
 Int 21 Fn 252A  P - Phar Lap 386/dos-extender Vmm - New Load Program For Deb
 Int 21 Fn 252B  Pu - Phar Lap 386/dos-extender - Create Unmapped Pages
 Int 21 Fn 252B  Pu - Phar Lap 386/dos-extender - Create Allocated Pages
 Int 21 Fn 252B  Pu - Phar Lap 386/dos-extender - Create Physical Device Page
 Int 21 Fn 252B  Pu - Phar Lap 386/dos-extender - Map Data File
 Int 21 Fn 252B  Pu - Phar Lap 386/dos-extender - Get Page Types
 Int 21 Fn 252B  P - Phar Lap 386/dos-extender - Virtual Memory Management -
 Int 21 Fn 252B  Pu - Phar Lap 386/dos-extender - Free Physical Pages
 Int 21 Fn 252B  P - Phar Lap 386/dos-extender V4.1 - Get Pagetable Entry/pag
 Int 21 Fn 252B  P - Phar Lap 386/dos-extender V4.1 - Set Pagetable Entry/pag
 Int 21 Fn 252B  P - Phar Lap 386/dos-extender V4.1+ - Map Data File At File
 Int 21 Fn 252C  P - Phar Lap 386/dos-ext Vmm V3.0 - Add Unmapped Pages At En
 Int 21 Fn 252D  P - Phar Lap 386/dos-extender Vmm V2.3+ - Close Vmm File Han
 Int 21 Fn 252E  P - Phar Lap 386/dos-extender Vmm V2.3+ - Get/set Vmm Parame
 Int 21 Fn 252F  P - Phar Lap 386/dos-ext Vmm V3.0 - Write Record To Vmm Page
 Int 21 Fn 2530  P - Phar Lap 386/dos-ext Vmm V2.3+ - Set Size Of Buffer For
 Int 21 Fn 2531  P - Phar Lap 386/dos-extender Vmm V3.0 - Read/write Ldt Desc
 Int 21 Fn 2532  P - Phar Lap 386/dos-extender - Get Exception Handler Vector
 Int 21 Fn 2533  P - Phar Lap 386/dos-extender - Set Exception Handler Vector
 Int 21 Fn 2534  P - Phar Lap 386/dos-extender V3.0+ - Get Interrupt Flag
 Int 21 Fn 2535  P - Phar Lap 386/dos-extender V3.0+ - Read/write System Regi
 Int 21 Fn 2536  P - Phar Lap 386/dos-ext Vmm V3.0+ - Min/max Extended/conv M
 Int 21 Fn 2537  P - Phar Lap 386/dos-ext Vmm V3.0 - Allocate DOS Memory Abov
 Int 21 Fn 2538  P - Phar Lap 386/dos-ext Vmm V3.0 - Read Protmode Regs After
 Int 21 Fn 2539  P - Phar Lap 386/dos-ext Vmm V3.0 - Get Offset Of .exp File
 Int 21 Fn 253A  P - Phar Lap 386/dos-extender V3.0+ - Install Mod. Seg Failu
 Int 21 Fn 253B  P - Phar Lap 386/dos-extender V3.0+ - Jump To Real Mode Code
 Int 21 Fn 253C  P - Phar Lap 386/dos-extender Vmm V3.0+ - Shrink 386|vmm Swa
 Int 21 Fn 253D  P - Phar Lap 386/dos-extender V4.0+ - Read/write Idt Descrip
 Int 21 Fn 253F  Pu - Phar Lap 386/dos-extenderr V6.0+ - Allocate Ldt Descrip
 Int 21 Fn 2540  Pu - Phar Lap 386/dos-extenderr V6.0+ - Force Alias Of Segme
 Int 21 Fn 2544  Pu - Phar Lap 386/dos-extenderr V6.0+ - Free Dll
 Int 21 Fn 2545  Pu - Phar Lap 386/dos-extenderr V6.0+ - Get/set Procedure Ad
 Int 21 Fn 2546  Pu - Phar Lap 386/dos-extenderr V6.0+ - Get Module Handle
 Int 21 Fn 25C0  P - Phar Lap 386/dos-extender - Allocate MS-dos Memory Block
 Int 21 Fn 25C1  P - Phar Lap 386/dos-extender - Release MS-dos Memory Block
 Int 21 Fn 25C2  P - Phar Lap 386/dos-extender - Modify MS-dos Memory Block
 Int 21 Fn 25C3  P - Phar Lap 386/dos-extender - Execute Program
 Int 21 Fn 26  - DOS 1+ - Create New Program Segment Prefix
 Int 21 Fn 27  - DOS 1+ - Random Block Read From Fcb File
 Int 21 Fn 28  - DOS 1+ - Random Block Write To Fcb File
 Int 21 Fn 29  - DOS 1+ - Parse Filename Into Fcb
 Int 21 Fn 2A  - DOS 1+ - Get System Date
 Int 21 Fn 2B  - DOS 1+ - Set System Date
 Int 21 Fn 2B  - Ai Architects - ??? - Installation Check
 Int 21 Fn 2B  - Super PC-kwik V3.20+ - Installation Check
 Int 21 Fn 2B  - Desqview - Installation Check
 Int 21 Fn 2B  - Elres V1.1 - Installation Check
 Int 21 Fn 2B01  - Quarterdeck DOS-up.sys V2.00 - Installation Check
 Int 21 Fn 2B01  - Tame V2.10+ - Installation Check
 Int 21 Fn 2B44  - PCanywhere Iv/lan - Installation Check
 Int 21 Fn 2C  - DOS 1+ - Get System Time
 Int 21 Fn 2D  - DOS 1+ - Set System Time
 Int 21 Fn 2D01  - PC-mix - Installation Check
 Int 21 Fn 2E  - DOS 1+ - Set Verify Flag
 Int 21 Fn 2F  - DOS 2+ - Get Disk Transfer Area Address
 Int 21 Fn 30  - DOS 2+ - Get Dos Version
 Int 21 Fn 30  - Phar Lap 386/dos-extender, Intel Code Builder - Installation
 Int 21 Fn 30  - Virus - "possessed" - Installation Check
 Int 21 Fn 3000  - Ctask 2.0+ - Installation Check
 Int 21 Fn 3000  - PC-mos/386 V3.0 - Installation Check/get Version
 Int 21 Fn 3022  - Stopprg V2.0 - Installation Check
 Int 21 Fn 30F1  - Virus - "dutch-555"/"quit 1992" - Installation Check
 Int 21 Fn 30FF  - Desq??? - Installation Check
 Int 21 Fn 31  - DOS 2+ - Terminate And Stay Resident
 Int 21 Fn 32  - DOS 2+ - Get Dos Drive Parameter Block For Specific Drive
 Int 21 Fn 33  - DOS 2+ - Extended Break Checking
 Int 21 Fn 3302  - DOS 3.x+ Internal - Get And Set Extended Control-break Che
 Int 21 Fn 3305  - DOS 4+ - Get Boot Drive
 Int 21 Fn 3306  - DOS 5+ - Get True Version Number
 Int 21 Fn 3306  - Cbis Powerlan - Network Redirector - ???
 Int 21 Fn 330F  - Virus - "burghofer" - Installation Check
 Int 21 Fn 3341  - Diet Disk V1.0 - Installation Check
 Int 21 Fn 33E0  - Virus - "oropax" - Installation Check
 Int 21 Fn 34  - DOS 2+ - Get Address Of Indos Flag
 Int 21 Fn 35  - DOS 2+ - Get Interrupt Vector
 Int 21 Fn 3501  P - Flashtek X-32vm - Allocate Protected-mode Selector
 Int 21 Fn 3502  P - Flashtek X-32vm - Deallocate Protected-mode Selector
 Int 21 Fn 3503  P - Flashtek X-32vm - Set Selector Base Address
 Int 21 Fn 3504  P - Flashtek X-32vm - Get Selector Base Address
 Int 21 Fn 3505  P - Flashtek X-32vm - Set Selector LIMit
 Int 21 Fn 350A  P - Flashtek X-32vm - Physical Address Mapping
 Int 21 Fn 350B  P - Flashtek X-32vm - Update And Return Available Free Memor
 Int 21 Fn 350C  P - Flashtek X-32vm - Allocate A Block Of Memory
 Int 21 Fn 350D  P - Flashtek X-32vm - Reserve Block Of Memory For 32-bit Sta
 Int 21 Fn 357F  - Virus - "agiplan"/"month 4-6" - Installation Check
 Int 21 Fn 36  - DOS 2+ - Get Free Disk Space
 Int 21 Fn 3700  - DOS 2+ - "switchar" - Get Switch Character
 Int 21 Fn 3701  - DOS 2+ - "switchar" - Set Switch Character
 Int 21 Fn 37  - DOS 2.x And 3.3+ Only - "availdev" - Specify \dev\ Prefix Us
 Int 21 Fn 37D0  - Diet V1.43e - Tsr Installation Check
 Int 21 Fn 37D1  - Diet V1.43e - Get Diet.exe Resident Segment
 Int 21 Fn 37D2  - Diet V1.43e - Get Tsr Control Flags
 Int 21 Fn 37D3  - Diet V1.43e - Set Tsr Control Flags
 Int 21 Fn 37D4  - Diet V1.43e - Get Tsr Options
 Int 21 Fn 37D5  - Diet V1.43e - Set Tsr Options
 Int 21 Fn 37D6  - Diet V1.43e - Get Temporary Directory Names
 Int 21 Fn 37D7  - Diet V1.43e - Set Temporary Directory Names
 Int 21 Fn 37DC  - Diet V1.43e - Set Address Of External Procedure
 Int 21 Fn 37DD  - Diet V1.43e - Release External Procedure
 Int 21 Fn 37DE  - Diet V1.43e - Read EMS Status
 Int 21 Fn 37DF  - Diet V1.43e - Unload Tsr
 Int 21 Fn 38  - DOS 2+ - Get Country-specific Information
 Int 21 Fn 38  - DOS 3+ - Set Country Code
 Int 21 Fn 39  - DOS 2+ - "mkdir" - Create Subdirectory
 Int 21 Fn 3A  - DOS 2+ - "rmdir" - Remove Subdirectory
 Int 21 Fn 3B  - DOS 2+ - "chdir" - Set Current Directory
 Int 21 Fn 3C  - DOS 2+ - "creat" - Create Or Truncate File
 Int 21 Fn 3D  - DOS 2+ - "open" - Open Existing File
 Int 21 Fn 3DFF  - Virus - "jd-448" - Installation Check
 Int 21 Fn 3E  - DOS 2+ - "close" - Close File
 Int 21 Fn 3F  - DOS 2+ - "read" - Read From File Or Device
 Int 21 Fn 3F  - Turbo Debug Hardware Breakpoints - Read Status Block
 Int 21 Fn 3F  - PC/tcp Ipcust.sys - Read Configuration Data
 Int 21 Fn 3F  - Workgrp.sys - Get Entry Point
 Int 21 Fn 3F  - Bw-tcp - Get Driver Info