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 INT 21h, 00h    Program termination
 INT 21h, 01h    Keyboard input
 INT 21h, 02h    Display output
 INT 21h, 03h    Aux input
 INT 21h, 04h    Aux output
 INT 21h, 05h    Printer output
 INT 21h, 06h    Direct console I/O character
 INT 21h, 07h    Direct console input, no echo
 INT 21h, 08h    Stdin input, no echo
 INT 21h, 09h    Print string
 INT 21h, 0Ah    Buffered keyboard input
 INT 21h, 0Bh    Check standard input status
 INT 21h, 0Ch    Clear keyboard buffer
 INT 21h, 0Dh    Disk reset
 INT 21h, 0Eh    Select disk
 INT 21h, 0Fh    Open disk file
 INT 21h, 10h    Close disk file
 INT 21h, 11h    Search first using FCB
 INT 21h, 12h    Search next using FCB
 INT 21h, 13h    Delete file via FCB
 INT 21h, 14h    Sequential disk file read
 INT 21h, 15h    Sequential disk record write
 INT 21h, 16h    Create a disk file
 INT 21h, 17h    Rename file via FCB
 INT 21, 18h     DOS internal - UNUSED
 INT 21h, 19h    Get default disk number
 INT 21h, 1Ah    Set disk transfer area address
 INT 21h, 1Bh    Get allocation table information for default drive
 INT 21h, 1Ch    Get allocation table information for specific device
 INT 21h, 1Dh    Dos internal - Unused
 INT 21h, 1Eh    Dos internal - Unused
 INT 21h, 1Fh    Get default drive parameter block                 (Internal)
 INT 21h, 21h    Random disk record read
 INT 21h, 22h    Random disk record write
 INT 21h, 23h    Get file size
 INT 21h, 24h    Set random record field
 INT 21h, 25h    Set interrupt vector
 INT 21h, 26h    Create PSP
 INT 21h, 27h    Random block read
 INT 21h, 28h    Random block write
 INT 21h, 29h    Parse filename
 INT 21h, 2Ah    Get current date
 INT 21h, 2Bh    Set current date (+ DESQView inst. check)
 INT 21h, 2Bh    PC Tools v5.1 PC-CACHE - Installation check
 INT 21h, 2Ch    Get current time
 INT 21h, 2Dh    Set current time
 INT 21h, 2Eh    Set verify flag
 INT 21h, 2Fh    Get disk transfer area address
 INT 21h, 30h    Get dos version
 INT 21h, 31h    Terminate but stay resident
 INT 21h, 32h    Get DOS Drive Parameter Block                     (Internal)
 INT 21h, 33h    Extended control-break checking
 INT 21h, 33h    DOS 4.0 - Get boot drive
 INT 21h, 34h    In-DOS flag                                       (Internal)
 INT 21h, 35h    Get interrupt vector
 INT 21h, 36h    Get disk space
 INT 21h, 37h    Switchar/availdev                                 (Internal)
 INT 21h, 38h    Get/Set country-dependent information
 INT 21h, 39h    Create a subdirectory (MKDIR)
 INT 21h, 3Ah    Remove a directory entry (RMDIR)
 INT 21h, 3Bh    Change the current directory (CHDIR)
 INT 21h, 3Ch    Create a file with handle (CREAT)
 INT 21h, 3Dh    Open disk file with handle
 INT 21h, 3Eh    Close a file with handle
 INT 21h, 3Fh    Read from file with handle
 INT 21h, 40h    Write to file with handle
 INT 21h, 41h    Delete a file (UNLINK)
 INT 21h, 42h    Move file read/write pointer (LSEEK)
 INT 21h, 43h    Get/set file attributes (CHMOD)
 INT 21h, 44h    IOCTL
 INT 21h, 45h    Create duplicate handle (DUP)
 INT 21h, 46h    Force duplicate handle (FORCDUP)
 INT 21h, 47h    Get current directory
 INT 21h, 48h    Allocate memory
 INT 21h, 49h    Free memory
 INT 21h, 4Ah    Adjust memory block size (SETBLOCK)
 INT 21h, 4Bh    Load or execute (EXEC)
 INT 21h, 4Ch    Quit with exit code (EXIT)
 INT 21h, 4Dh    Get exit code of subprogram (WAIT)
 INT 21h, 4Eh    Find first ASCIIZ (FIND FIRST)
 INT 21h, 4Fh    Find next ASCIIZ (FIND NEXT)
 INT 21h, 50h    Set PSP segment                                   (Internal)
 INT 21h, 51h    Get PSP segment                                   (Internal)
 INT 21h, 52h    Get DOS lists                                     (Internal)
 INT 21h, 53h    Translate BPB                                     (Internal)
 INT 21h, 54h    Get verify flag
 INT 21h, 55h    Create PSP                                        (Internal)
 INT 21h, 56h    Rename a file
 INT 21h, 57h    Get/set file's date/time
 INT 21h, 58h    Get/set memory allocation strategy      (DOS 3.x - Internal)
 INT 21h, 59h    Get extended error code                            (DOS 3.x)
 INT 21h, 5Ah    Create temporary file                              (DOS 3.x)
 INT 21h, 5Bh    Create new file                                    (DOS 3.x)
 INT 21h, 5Ch    Lock/unlock file access                            (DOS 3.x)
 INT 21h, 5Dh    DOS internal functions                  (DOS 3.x - Internal)
 INT 21h, 5Eh    Microsoft Networks
 INT 21h, 60h    Resolve path string to fully qualified path        (DOS 3.x)
 INT 21h, 62h    Get PSP segment                                    (DOS 3.x)
 INT 21h, 65h    Get extended country information                   (DOS 3.3)
 INT 21h, 66h    Get/set global code page table                     (DOS 3.3)
 INT 21h, 67h    Set handle count                                   (DOS 3.3)
 INT 21h, 68h    Commit file, write all buffered data to disk       (DOS 3.3)
 INT 21h, 69h    Get disk serial number                  (DOS 4.0 - Internal)
 INT 21h, 6Ah    Internal - ??                                      (DOS 4.x)
 INT 21h, 6Bh    Internal - ??                                      (DOS 4.x)
 INT 21h, 6Ch    Extended Open/Create                               (DOS 4.0)
 INT 21h, Internal ??? (Called by Microsoft C 4.0 startup code)
 INT 21h, B6h    Extended file attributes                         (Novell II)
 INT 21h, B8h    Print jobs                                (Novell Adv. 2.0+)
 INT 21h, BBh    Set end of job status                           (Novell 4.0)
 INT 21h, BCh    Log physical record                             (Novell 4.6)
 INT 21h, BDh    Release physical record                         (Novell 4.6)
 INT 21h, BEh    Clear physical record                           (Novell 4.6)
 INT 21h, BFh    Log record (FCB)                                (Novell 4.6)
 INT 21h, C0h    Release record (FCB)                            (Novell 4.6)
 INT 21h, C1h    Clear record (FCB)                              (Novell 4.6)
 INT 21h, C2h    Lock physical record set                        (Novell 4.6)
 INT 21h, C3h    Release physical record set                     (Novell 4.6)
 INT 21h, C4h    Clear physical record set                       (Novell 4.6)
 INT 21h, C5h    Semaphores                                      (Novell 4.6)
 INT 21h, C6h    Get or set lock mode                            (Novell 4.6)
 INT 21h, C7h    TTS                                             (Novell 4.0)
 INT 21h, C8h    Begin logical file locking                      (Novell 4.0)
 INT 21h, C9h    End logical file locking                        (Novell 4.0)
 INT 21h, CAh    Log personal file (FCB)                         (Novell 4.0)
 INT 21h, CBh    Lock file set                                   (Novell 4.0)
 INT 21h, CCh    Release file (FCB)                              (Novell 4.0)
 INT 21h, CDh    Release file set                                (Novell 4.0)
 INT 21h, CEh    Clear file (FCB)                                (Novell 4.0)
 INT 21h, CFh    Clear file set                                  (Novell 4.0)
 INT 21h, D0h    Log logical record                              (Novell 4.6)
 INT 21h, D1h    Lock logical record set                         (Novell 4.6)
 INT 21h, D2h    Release logical record                          (Novell 4.0)
 INT 21h, D3h    Release logical record set                      (Novell 4.0)
 INT 21h, D4h    Clear logical record                            (Novell 4.0)
 INT 21h, D5h    Clear logical record set                        (Novell 4.0)
 INT 21h, D6h    End of job                                      (Novell 4.0)
 INT 21h, D7h    System logout                                   (Novell 4.0)
 INT 21h, DAh    Get volume statistics                           (Novell 4.0)
 INT 21h, DBh    Get number of local drives                      (Novell 4.0)
 INT 21h, DCh    Get station number                              (Novell 4.0)
 INT 21h, DDh    Set error mode                                  (Novell 4.0)
 INT 21h, DEh    Set broadcast mode                              (Novell 4.0)
 INT 21h, DFh    Capture                                         (Novell 4.0)
 INT 21h, E0h    Print spooling                                  (Novell 4.0)
 INT 21h, E1h    Broadcast messages                              (Novell 4.0)
 INT 21h, E2h    Directory functions                             (Novell 4.0)
 INT 21h, E3h    Connection control                              (Novell 4.0)
 INT 21h, E4h    Set file attributes (FCB),                      (Novell 4.0)
 INT 21h, E5h    Update file size (FCB)                          (Novell 4.0)
 INT 21h, E6h    Copy file to file (FCB)                         (Novell 4.0)
 INT 21h, E7h    Get file server date and time                   (Novell 4.0)
 INT 21h, E8h    Set FCB re-open mode                            (Novell 4.6)
 INT 21h, E9h    Shell's "get base status"                       (Novell 4.6)
 INT 21h, EAh    Return shell version,                           (Novell 4.6.)
 INT 21h, EBh    Log file,                                       (Novell 4.6.)
 INT 21h, ECh    Release file.                                   (Novell 4.6)
 INT 21h, EDh    Clear file                                          (Novell)
 INT 21h, EEh    Get physical station number                     (Novell 4.6)
 INT 21h, EFh    Get drive info                            (Novell Adv. 1.0+)
 INT 21h, F0h    Connection id                             (Novell Adv. 1.0+)
 INT 21h, F1h    File server connection                    (Novell Adv. 1.0+)
 INT 21h, F2h    Novell Netware - ???
 INT 21h, F3h    File server file copy                     (Novell Adv. 2.0+)
 INT 21h, F3h    File server file copy                     (Novell Adv. 2.0+)
 INT 21h, E4h    DoubleDos - INSTALLATION CHECK    (INT 21h, E4h - DoubleDos)
 INT 21h, EBh    DoubleDos - Turn on task switching  (INT 21h, EBh - DoubleDos)
 INT 21h, ECh    DoubleDos - Get virtual screen address  (INT 21h, ECh - DoubleDos)
 INT 21h, EEh    DoubleDos - Give away time to other tasks (INT 21h, EEh - DoubleDos)
 INT 21h, F8h    Set oem int 21 handler
 INT 21h, F9h    OEM Function
 INT 21h, FAh    OEM Function
 INT 21h, FBh    OEM Function
 INT 21h, FCh    OEM Function
 INT 21h, FDh    OEM Function
 INT 21h, FEh    OEM Function
 INT 21h, FFh    OEM Function
 INT 21h, FFh    CED - Installable commands