AOH :: INT-C.TXT
PC Interrupt Listing Part 3 of 8
|
Interrupt List, part 3 of 8
This compilation is Copyright (c) 1989,1990,1991,1992 Ralf Brown
----------20---------------------------------
INT 20 - Minix - SEND/RECEIVE MESSAGE
AX = process ID of other process
BX -> message
CX = 1 send
2 receive
3 send&receive
Note: the message contains the system call number (numbered as in V7
Unix(tm)) and the call parameters
----------20---------------------------------
INT 20 - DOS 1+ - TERMINATE PROGRAM
CS = PSP segment
Return: never
Note: (see INT 21/AH=00h)
SeeAlso: INT 21/AH=00h,INT 21/AH=4Ch
----------2100-------------------------------
INT 21 - DOS 1+ - TERMINATE PROGRAM
AH = 00h
CS = PSP segment
Notes: Microsoft recomments using INT 21/AH=4Ch for DOS 2+
execution continues at address stored in INT 22 after DOS performs
whatever cleanup it needs to do
if the PSP is its own parent, the process's memory is not freed; if
INT 22 additionally points into the terminating program, the
process is effectively NOT terminated
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=26h,AH=31h,AH=4Ch,INT 20,INT 22
----------2101-------------------------------
INT 21 - DOS 1+ - READ CHARACTER FROM STANDARD INPUT, WITH ECHO
AH = 01h
Return: AL = character read
Notes: ^C/^Break are checked, and INT 23 executed if read
character is echoed to standard output
standard input is always the keyboard and standard output the screen
under DOS 1.x, but they may be redirected under DOS 2+
SeeAlso: AH=06h,AH=07h,AH=08h,AH=0Ah
----------2102-------------------------------
INT 21 - DOS 1+ - WRITE CHARACTER TO STANDARD OUTPUT
AH = 02h
DL = character to write
Return: AL = last character output (despite the official docs which state
nothing is returned) (at least DOS 3.3-5.0)
Notes: ^C/^Break are checked, and INT 23 executed if pressed
standard output is always the screen under DOS 1.x, but may be
redirected under DOS 2+
the last character output will be the character in DL unless DL=09h
on entry, in which case AL=20h as tabs are expanded to blanks
SeeAlso: AH=06h,AH=09h
----------2103-------------------------------
INT 21 - DOS 1+ - READ CHARACTER FROM STDAUX
AH = 03h
Return: AL = character read
Notes: keyboard checked for ^C/^Break, and INT 23 executed if detected
STDAUX is usually the first serial port
SeeAlso: AH=04h,INT 14/AH=02h,INT E0/CL=03h
----------2104-------------------------------
INT 21 - DOS 1+ - WRITE CHARACTER TO STDAUX
AH = 04h
DL = character to write
Notes: keyboard checked for ^C/^Break, and INT 23 executed if detected
STDAUX is usually the first serial port
if STDAUX is busy, this function will wait until it becomes free
SeeAlso: AH=03h,INT 14/AH=01h,INT E0/CL=04h
----------2105-------------------------------
INT 21 - DOS 1+ - WRITE CHARACTER TO PRINTER
AH = 05h
DL = character to print
Notes: keyboard checked for ^C/^Break, and INT 23 executed if detected
STDPRN is usually the first parallel port, but may be redirected under
DOS 2+
if the printer is busy, this function will wait
SeeAlso: INT 17/AH=00h
----------2106-------------------------------
INT 21 - DOS 1+ - DIRECT CONSOLE OUTPUT
AH = 06h
DL = character (except FFh)
Return: AL = character output (despite official docs which state nothing is
returned) (at least DOS 3.3-5.0)
Notes: does not check ^C/^Break
writes to standard output, which is always the screen under DOS 1.x,
but may be redirected under DOS 2+
SeeAlso: AH=02h,AH=09h
----------2106--DLFF-------------------------
INT 21 - DOS 1+ - DIRECT CONSOLE INPUT
AH = 06h
DL = FFh
Return: ZF set if no character available
ZF clear if character available
AL = character read
Notes: ^C/^Break are NOT checked
if the returned character is 00h, the user pressed a key with an
extended keycode, which will be returned by the next call of this
function
reads from standard input, which is always the keyboard under DOS 1.x,
but may be redirected under DOS 2+
SeeAlso: AH=0Bh
----------2107-------------------------------
INT 21 - DOS 1+ - DIRECT CHARACTER INPUT, WITHOUT ECHO
AH = 07h
Return: AL = character read from standard input
Notes: does not check ^C/^Break
standard input is always the keyboard under DOS 1.x, but may be
redirected under DOS 2+
if the interim console flag is set (see AX=6301h), partially-formed
double-byte characters may be returned
SeeAlso: AH=01h,AH=06h,AH=08h,AH=0Ah
----------2108-------------------------------
INT 21 - DOS 1+ - CHARACTER INPUT WITHOUT ECHO
AH = 08h
Return: AL = character read from standard input
Notes: ^C/^Break are checked, and INT 23 executed if detected
standard input is always the keyboard under DOS 1.x, but may be
redirected under DOS 2+
if the interim console flag is set (see AX=6301h), partially-formed
double-byte characters may be returned
SeeAlso: AH=01h,AH=06h,AH=07h,AH=0Ah,AH=64h
----------2109-------------------------------
INT 21 - DOS 1+ - WRITE STRING TO STANDARD OUTPUT
AH = 09h
DS:DX -> '$'-terminated string
Return: AL = 24h (the '$' terminating the string, despite official docs which
state that nothing is returned) (at least DOS 3.3-5.0)
Notes: ^C/^Break checked, and INT 23 called if pressed
standard output is always the screen under DOS 1.x, but may be
redirected under DOS 2+
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=02h,AH=06h"OUTPUT"
----------210A-------------------------------
INT 21 - DOS 1+ - BUFFERED INPUT
AH = 0Ah
DS:DX -> buffer (see below)
Return: buffer filled with user input
Notes: ^C/^Break checked, and INT 23 called if detected
reads from standard input, which may be redirected under DOS 2+
if the maximum buffer size (see below) is set to 00h, this call returns
immediately without reading any input
SeeAlso: AH=0Ch,INT 2F/AX=4810h
Format of input buffer:
Offset Size Description
00h BYTE maximum characters buffer can hold
01h BYTE (input) number of chars from last input which may be recalled
(return) number of characters actually read, excluding CR
02h N BYTEs actual characters read, including the final carriage return
----------210A00-----------------------------
INT 21 - WCED v1.6 - INSTALLATION CHECK
AX = 0A00h
DS:DX -> 6-byte buffer whose first two bytes must be 00h
Return: buffer offset 02h-05h filled with "Wced" if installed
Note: WCED is a free command-line editor and history utility by Stuart
Russell
SeeAlso: AH=FFh"CED"
----------210B-------------------------------
INT 21 - DOS 1+ - GET STDIN STATUS
AH = 0Bh
Return: AL = 00h if no character available
= FFh if character is available
Notes: ^C/^Break checked, and INT 23 called if pressed
standard input is always the keyboard under DOS 1.x, but may be
redirected under DOS 2+
if the interim console flag is set (see AX=6301h), this function
returns AL=FFh if a partially-formed double-byte character is
available
SeeAlso: AH=06h"INPUT",AX=4406h
----------210B56-----------------------------
INT 21 - VIRUS - "Perfume" - INSTALLATION CHECK
AX = 0B56h
Return: AX = 4952h if resident
SeeAlso: AX=0D20h
----------210C-------------------------------
INT 21 - DOS 1+ - FLUSH BUFFER AND READ STANDARD INPUT
AH = 0Ch
AL = STDIN input function to execute after flushing buffer
other registers as appropriate for the input function
Return: as appropriate for the specified input function
Note: if AL is not one of 01h,06h,07h,08h, or 0Ah, the buffer is flushed but
no input is attempted
SeeAlso: AH=01h,AH=06h"INPUT",AH=07h,AH=08h,AH=0Ah
----------210D-------------------------------
INT 21 - DOS 1+ - DISK RESET
AH = 0Dh
Notes: writes all modified disk buffers to disk, but does not update directory
information (that is only done when files are closed or a SYNC call
is issued)
SeeAlso: AX=5D01h,INT 13/AH=00h,INT 2F/AX=1120h
----------210D20-----------------------------
INT 21 - VIRUS - "Crazy Imp" - INSTALLATION CHECK
AX = 0D20h
Return: AX = 1971h if resident
SeeAlso: AX=0B56h,AH=30h/DX=ABCDh
----------210E-------------------------------
INT 21 - DOS 1+ - SELECT DEFAULT DRIVE
AH = 0Eh
DL = new default drive (00h = A:, 01h = B:, etc)
Return: AL = number of potentially valid drive letters
Notes: under Novell NetWare, the return value is always 32, the number of
drives that NetWare supports
under DOS 3+, the return value is the greatest of 5, the value of
LASTDRIVE= in CONFIG.SYS, and the number of drives actually present
on a DOS 1.x/2.x single-floppy system, AL returns 2 since the floppy
may be accessed as either A: or B:
otherwise, the return value is the highest drive actually present
DOS 1.x supports a maximum of 16 drives, 2.x a maximum of 63 drives,
and 3+ a maximum of 26 drives
SeeAlso: AH=19h,AH=3Bh,AH=DBh
----------210F-------------------------------
INT 21 - DOS 1+ - OPEN FILE USING FCB
AH = 0Fh
DS:DX -> unopened File Control Block (see below)
Return: AL = status
00h successful
FFh file not found or access denied
Notes: (DOS 3.1+) file opened for read/write in compatibility mode
an unopened FCB has the drive, filename, and extension fields filled
in and all other bytes cleared
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=10h,AH=16h,AH=3Dh
Format of File Control Block:
Offset Size Description
-7 BYTE extended FCB if FFh
-6 5 BYTEs reserved
-1 BYTE file attribute if extended FCB
00h BYTE drive number (0 = default, 1 = A, etc)
01h 8 BYTEs blank-padded file name
09h 3 BYTEs blank-padded file extension
0Ch WORD current block number
0Eh WORD logical record size
10h DWORD file size
14h WORD date of last write (see AX=5700h)
16h WORD time of last write (see AX=5700h) (DOS 1.1+)
18h 8 BYTEs reserved (see below)
20h BYTE record within current block
21h DWORD random access record number (if record size is > 64 bytes, high
byte is omitted)
Note: to use an extended FCB, you must specify the address of the FFh flag at
offset -7, rather than the address of the drive number field
Format of reserved field for DOS 1.0:
Offset Size Description
16h WORD location in directory (if high byte = FFh, low byte is device
ID)
18h WORD number of first cluster in file
1Ah WORD current absolute cluster number on disk
1Ch WORD current relative cluster number within file
(0 = first cluster of file, 1 = second cluster, etc.)
1Eh BYTE dirty flag (00h = not dirty)
1Fh BYTE unused
Format of reserved field for DOS 1.10-1.25:
Offset Size Description
18h BYTE bit 7: set if logical device
bit 6: not dirty
bits 5-0: disk number or logical device ID
19h WORD starting cluster number on disk
1Bh WORD current absolute cluster number on disk
1Dh WORD current relative cluster number within file
1Fh BYTE unused
Format of reserved field for DOS 2.x:
Offset Size Description
18h BYTE bit 7: set if logical device
bit 6: set if open???
bits 5-0: ???
19h WORD starting cluster number on disk
1Bh WORD ???
1Dh BYTE ???
1Eh BYTE ???
1Fh BYTE ???
Format of reserved field for DOS 3.x:
Offset Size Description
18h BYTE number of system file table entry for file
19h BYTE attributes
bits 7,6: 00 = SHARE.EXE not loaded, disk file
01 = SHARE.EXE not loaded, character device
10 = SHARE.EXE loaded, remote file
11 = SHARE.EXE loaded, local file
bits 5-0: low six bits of device attribute word
---SHARE.EXE loaded, local file (DOS 3.x and 5.0)---
1Ah WORD starting cluster of file on disk
1Ch WORD (DOS 3.x) offset within SHARE of sharing record (see AH=52h)
(DOS 5.0) unique sequence number of sharing record
1Eh BYTE file attribute
1Fh BYTE ???
---SHARE.EXE loaded, remote file---
1Ah WORD number of sector containing directory entry
1Ch WORD relative cluster within file of last cluster accessed
1Eh BYTE absolute cluster number of last cluster accessed
1Fh BYTE ???
---SHARE.EXE not loaded---
1Ah BYTE (low byte of device attribute word AND 0Ch) OR open mode
1Bh WORD starting cluster of file
1Dh WORD number of sector containing directory entry
1Fh BYTE number of directory entry within sector
Note: if FCB opened on character device, DWORD at 1Ah is set to the address
of the device driver header, then the BYTE at 1Ah is overwritten.
----------2110-------------------------------
INT 21 - DOS 1+ - CLOSE FILE USING FCB
AH = 10h
DS:DX -> File Control Block (see AH=0Fh)
Return: AL = status
00h successful
FFh failed
Notes: a successful close forces all disk buffers used by the file to be
written and the directory entry to be updated
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=16h,AH=3Eh
----------2111-------------------------------
INT 21 - DOS 1+ - FIND FIRST MATCHING FILE USING FCB
AH = 11h
DS:DX -> unopened FCB (see AH=0Fh), may contain '?' wildcards
Return: AL = status
00h successful
[DTA] unopened FCB for first matching file
FFh no matching filename, or bad FCB
Notes: the type of the returned FCB depends on whether the input FCB was a
normal or an extended FCB
for extended FCBs with search attribute 08h, the volume label (if any)
will be returned even if the current directory is not the root dir.
DOS 3+ also allows the '*' wildcard
the search FCB must not be modified if AH=12h will be used to continue
searching; DOS 3.3 has set the following parts of the FCB:
0Ch BYTE ???
0Dh WORD directory entry number of matching file
0Fh WORD cluster number of current directory
11h 4 BYTEs ???
15h BYTE drive number (1=A:)
at least for DOS 3.3, the unopened FCB in the DTA is actually the drive
number followed by the file's directory entry
SeeAlso: AH=12h,AH=1Ah,AH=4Eh,INT 2F/AX=111Bh
----------2112-------------------------------
INT 21 - DOS 1+ - FIND NEXT MATCHING FILE USING FCB
AH = 12h
DS:DX -> unopened FCB (see AH=0Fh)
Return: AL = status
00h successful
[DTA] = unopened FCB
FFh no more matching filenames
Note: (see AH=11h)
assumes that successful FindFirst executed on search FCB before call
SeeAlso: AH=1Ah,AH=4Fh,INT 2F/AX=111Ch
----------2113-------------------------------
INT 21 - DOS 1+ - DELETE FILE USING FCB
AH = 13h
DS:DX -> unopened FCB (see AH=0Fh), filename filled with template for
deletion ('?' wildcards allowed)
Return: AL = status
00h one or more files successfully deleted
FFh no matching files or all were read-only or locked
Notes: DOS 1.25+ deletes everything in the current directory (including
subdirectories) and sets the first byte of the name to 00h (entry
never used) instead of E5h if called on an extended FCB with
filename '???????????' and bits 0-4 of the attribute set (bits 1 and
2 for DOS 1.x). This may have originally been an optimization to
minimize directory searching after a mass deletion (DOS 1.25+ stop
the directory search upon encountering a never-used entry), but can
corrupt the filesystem under DOS 2+ because subdirectories are
removed without deleting the files they contain.
currently-open files should not be deleted
SeeAlso: AH=41h,INT 2F/AX=1113h
----------2114-------------------------------
INT 21 - DOS 1+ - SEQUENTIAL READ FROM FCB FILE
AH = 14h
DS:DX -> opened FCB (see AH=0Fh)
Return: AL = status
00h successful
01h end of file (no data)
02h segment wrap in DTA
03h end of file, partial record read
[DTA] = record read from file
Notes: reads a record of the size specified in the FCB beginning at the
current file position, then updates the current block and current
record fields in the FCB
if a partial record was read, it is zero-padded to the full size
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=15h,AH=1Ah,AH=3Fh,INT 2F/AX=1108h
----------2115-------------------------------
INT 21 - DOS 1+ - SEQUENTIAL WRITE TO FCB FILE
AH = 15h
DS:DX -> opened FCB (see AH=0Fh)
[DTA] = record to write
Return: AL = status
00h successful
01h disk full
02h segment wrap in DTA
Notes: writes a record of the size specified in the FCB beginning at the
current file position, then updates the current block and current
record fields in the FCB
if less than a full sector is written, the data is placed in a DOS
buffer to be written out at a later time
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=14h,AH=1Ah,AH=40h,INT 2F/AX=1109h
----------2116-------------------------------
INT 21 - DOS 1+ - CREATE OR TRUNCATE FILE USING FCB
AH = 16h
DS:DX -> unopened FCB (see AH=0Fh), wildcards not allowed
Return: AL = status
00h successful
FFh directory full or file exists and is read-only or locked
Notes: if file already exists, it is truncated to zero length
if an extended FCB is used, the file is given the attribute in the
FCB
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=10h,AH=3Ch
----------2117-------------------------------
INT 21 - DOS 1+ - RENAME FILE USING FCB
AH = 17h
DS:DX -> modified FCB (see also AH=0Fh)
the old filename ('?' wildcards OK) is in the standard location
while the new filename ('?' wildcards OK) is stored in the 11
bytes beginning at offset 11h
Return: AL = status
00h successfully renamed
FFh no matching files,file is read-only, or new name already exists
Note: subdirectories may be renamed using an extended FCB with the
appropriate attribute
SeeAlso: AH=0Fh,AH=13h,AH=56h,INT 2F/AX=1111h
----------2118-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 18h
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "get bit map of logged drives",
which is meaningless under MSDOS
SeeAlso: AH=1Dh,AH=1Eh,AH=20h,AX=4459h
----------2119-------------------------------
INT 21 - DOS 1+ - GET CURRENT DEFAULT DRIVE
AH = 19h
Return: AL = drive (00h = A:, 01h = B:, etc)
SeeAlo: AH=0Eh,AH=47h
----------211A-------------------------------
INT 21 - DOS 1+ - SET DISK TRANSFER AREA ADDRESS
AH = 1Ah
DS:DX -> Disk Transfer Area (DTA)
Notes: the DTA is set to PSP:0080h when a program is started
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=11h,AH=12h,AH=2Fh,AH=4Eh,AH=4Fh
----------211B-------------------------------
INT 21 - DOS 1+ - GET ALLOCATION INFORMATION FOR DEFAULT DRIVE
AH = 1Bh
Return: AL = sectors per cluster (allocation unit)
CX = bytes per sector
DX = total number of clusters
DS:BX -> media ID byte (see below)
Note: under DOS 1.x, DS:BX points at an actual copy of the FAT; later
versions return a pointer to a copy of the FAT's ID byte
SeeAlso: AH=1Ch,AH=36h
Values for media ID byte:
FFh floppy, double-sided, 8 sectors per track (320K)
FEh floppy, single-sided, 8 sectors per track (160K)
FDh floppy, double-sided, 9 sectors per track (360K)
FCh floppy, single-sided, 9 sectors per track (180K)
F9h floppy, double-sided, 15 sectors per track (1.2M)
F8h hard disk
F0h other
----------211C-------------------------------
INT 21 - DOS 1+ - GET ALLOCATION INFORMATION FOR SPECIFIC DRIVE
AH = 1Ch
DL = drive (00h = default, 01h = A:, etc)
Return: AL = sectors per cluster (allocation unit)
CX = bytes per sector
DX = total number of clusters
DS:BX -> media ID byte (see AH=1Bh)
Note: under DOS 1.x, DS:BX points at an actual copy of the FAT; later
versions return a pointer to a copy of the FAT's ID byte
SeeAlso: AH=1Bh,AH=36h
----------211D-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 1Dh
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "get bit map of read-only
drives", which is meaningless under MSDOS
SeeAlso: AH=18h,AH=1Eh,AH=20h,AX=4459h
----------211E-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 1Eh
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "set file attributes" which was
meaningless under MSDOS 1.x
SeeAlso: AH=18h,AH=1Dh,AH=20h
----------211F-------------------------------
INT 21 - DOS 1+ - GET DRIVE PARAMETER BLOCK FOR DEFAULT DRIVE
AH = 1Fh
Return: AL = status
00h successful
DS:BX -> Drive Parameter Block (DPB) (see below for DOS 1.x,
AH=32h for DOS 2+)
FFh invalid drive
Note: this call was undocumented prior to the release of DOS 5.0; however,
only the DOS 4+ version of the DPB has been documented
SeeAlso: AH=32h
Format of DOS 1.1 and MSDOS 1.25 drive parameter block:
Offset Size Description
00h BYTE sequential device ID
01h BYTE logical drive number (0=A:)
02h WORD bytes per sector
04h BYTE highest sector number within a cluster
05h BYTE shift count to convert clusters into sectors
06h WORD starting sector number of first FAT
08h BYTE number of copies of FAT
09h WORD number of directory entries
0Bh WORD number of first data sector
0Dh WORD highest cluster number (number of data clusters + 1)
0Fh BYTE sectors per FAT
10h WORD starting sector of directory
12h WORD address of allocation table
Note: the DOS 1.0 table is the same except that the first and last fields
are missing; see INT 21/AH=32h for the DOS 2+ version
----------2120-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 20h
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "get/set default user
(sublibrary) number", which is meaningless under MSDOS
SeeAlso: AH=18h,AH=1Dh,AH=1Eh,AX=4459h
----------2121-------------------------------
INT 21 - DOS 1+ - READ RANDOM RECORD FROM FCB FILE
AH = 21h
DS:DX -> opened FCB (see AH=0Fh)
Return: AL = status
00h successful
01h end of file, no data read
02h segment wrap in DTA, no data read
03h end of file, partial record read
[DTA] = record read from file
Notes: the record is read from the current file position as specified by the
random record and record size fields of the FCB
the file position is not updated after reading the record
if a partial record is read, it is zero-padded to the full size
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=14h,AH=22h,AH=27h,AH=3Fh
----------2122-------------------------------
INT 21 - DOS 1+ - WRITE RANDOM RECORD TO FCB FILE
AH = 22h
DS:DX -> opened FCB (see AH=0Fh)
[DTA] = record to write
Return: AL = status
00h successful
01h disk full
02h segment wrap in DTA
Notes: the record is written to the current file position as specified by the
random record and record size fields of the FCB
the file position is not updated after writing the record
if the record is located beyond the end of the file, the file is
extended but the intervening data remains uninitialized
if the record only partially fills a disk sector, it is copied to a
DOS disk buffer to be written out to disk at a later time
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=15h,AH=21h,AH=28h,AH=40h
----------2123-------------------------------
INT 21 - DOS 1+ - GET FILE SIZE FOR FCB
AH = 23h
DS:DX -> unopened FCB (see AH=0Fh), wildcards not allowed
Return: AL = status
00h successful (matching file found)
FCB random record field filled with size in records, rounded up
to next full record
FFh failed (no matching file found)
Note: not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=42h
----------2124-------------------------------
INT 21 - DOS 1+ - SET RANDOM RECORD NUMBER FOR FCB
AH = 24h
DS:DX -> opened FCB (see AH=0Fh)
Notes: computes the random record number corresponding to the current record
number and record size, then stores the result in the FCB
normally used when switching from sequential to random access
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=21h,AH=27h,AH=42h
----------2125-------------------------------
INT 21 - DOS 1+ - SET INTERRUPT VECTOR
AH = 25h
AL = interrupt number
DS:DX -> new interrupt handler
Notes: this function is preferred over direct modification of the interrupt
vector table
some DOS extenders place an API on this function, as it is not
directly meaningful in protected mode
SeeAlso: AX=2501h,AH=35h
----------212501-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - RESET DOS EXTENDER DATA STRUCTURES
AX = 2501h
SS = application's original SS or DS (FlashTek X-32VM)
Return: CF clear if successful
CF set on error
caller is operating on X-32 stack (FlashTek X-32VM)
Notes: Phar Lap uses INT 21/AH=25h as the entry point for all 386/DOS-Extender
system calls. Only available when directly using 386/DOS-Extender or
a compatible DOS extender, or when using a product that was created
using 386-DOS/Extender or a compatible
this function is also supported by FlashTek X-32VM
SeeAlso: AH=30h"Phar Lap"
----------212502-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET PROTECTED-MODE INTERRUPT VECTOR
AX = 2502h
CL = interrupt number
Return: CF clear
ES:EBX = CS:EIP of protected-mode interrupt handler
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2503h,AX=2504h,INT 31/AX=0204h
----------212503-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET REAL-MODE INTERRUPT VECTOR
AX = 2503h
CL = interrupt number
Return: CF clear
EBX = CS:IP of real-mode interrupt handler
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2502h,AX=2504h,AH=35h,INT 31/AX=0200h
----------212504-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - SET PROTECTED-MODE INTERRUPT VECTOR
AX = 2504h
CL = interrupt number
DS:EDX = CS:EIP of protected-mode interrupt handler
Return: CF clear
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2502h,AX=2505h,INT 31/AX=0205h
----------212505-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - SET REAL-MODE INTERRUPT VECTOR
AX = 2505h
CL = interrupt number
EBX = CS:IP of real-mode interrupt handler
Return: CF clear
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2503h,AX=2504h,INT 31/AX=0201h
----------212506-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - SET INT TO ALWAYS GAIN CONTRL IN PROT MODE
AX = 2506h
CL = interrupt number
DS:EDX = CS:EIP of protected-mode interrupt handler
Return: CF clear
Notes: this function modifies both the real-mode low-memory interrupt
vector table and the protected-mode Interrupt Descriptor Table (IDT)
interrupts occurring in real mode are resignaled in protected mode
this function is also supported by FlashTek X-32VM
----------212507-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - SET REAL- & PROTECTED-MODE INT VECTORS
AX = 2507h
CL = interrupt numbern
DS:EDX = CS:EIP of protected-mode interrupt handler
EBX = CS:IP of real-mode interrupt handler
Return: CF clear
Notes: interrupts are disabled until both vectors have been modified
this function is also supported by FlashTek X-32VM
SeeAlso: AX=2504h,AX=2505h
----------212508-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET SEGMENT LINEAR BASE ADDRESS
AX = 2508h
BX = segment selector
Return: CF clear if successful
ECX = linear base address of segment
CF set if invalid segment selector
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2509h
----------212509-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - CONVERT LINEAR TO PHYSICAL ADDRESS
AX = 2509h
EBX = linear address to convert
Return: CF clear if successful
ECX = physical address (carry flag clear)
CF set if linear address not mapped in page tables
SeeAlso: AX=2508h
----------212509-----------------------------
INT 21 - FlashTek X-32VM - GET SYSTEM SEGMENTS AND SELECTORS
AX = 2509h
Return: CF clear
EAX high word = default DS
AX = alias for 16-bit data segment
BX = real mode code segment
EDX high word = selector covering full 4GB address space
DX = default SS
ESI high word = PSP selector
SI = environment selector
----------21250A-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - MAP PHYSICAL MEMORY AT END OF SEGMENT
AX = 250Ah
ES = segment selector in the Local Descriptor Table (LDT) of segment
to modify
EBX = physical base address of memory to map (multiple of 4K)
ECX = number of physical 4K pages to map
Return: CF clear if successful
EAX = 32-bit offset in segment of mapped memory
CF set on error
EAX = error code
08h insufficient memory to create page tables
09h invalid segment selector
SeeAlso: INT 31/AX=0800h
----------21250C-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET HARDWARE INTERRUPT VECTORS
AX = 250Ch
Return: CF clear
AL = base interrupt vector for IRQ0-IRQ7
AH = base interrupt vector for IRQ8-IRQ15
BL = interrupt vector for BIOS print screen function (Phar Lap only)
Note: this function is also supported by FlashTek X-32VM
SeeAlso: INT 31/AX=0400h,INT 67/AX=DE0Ah
----------21250D-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET REAL-MODE LINK INFORMATION
AX = 250Dh
Return: CF clear
EAX = CS:IP of real-mode callback procedure that will call through
from real mode to a protected-mode routine
EBX = 32-bit real-mode address of intermode call data buffer
ECX = size in bytes of intermode call data buffer
ES:EDX = protected-mode address of intermode call data buffer
Notes: this function is also supported by FlashTek X-32VM
X-32VM guarantees the intermode buffer to be at least 4 KB
SeeAlso: AX=250Eh
Call real-mode callback with:
STACK: DWORD offset to protected-mode code
WORD placeholder for protected-mode CS
DWORD pointer to selector structure (see below)
or 0000h:0000h for defaults
var parameters for protected-mode procedure
Return: via FAR return
Format of selector structure:
Offset Size Description
00h WORD protected-mode GS selector
02h WORD protected-mode FS selector
04h WORD protected-mode ES selector
06h WORD protected-mode DS selector
----------21250E-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - CALL REAL-MODE PROCEDURE
AX = 250Eh
EBX = CS:IP of real-mode procedure to call
ECX = number of two-byte words to copy from protected-mode stack
to real-mode stack
Return: CF clear if successful
all segment registers unchanged
all general registers contain values set by real-mode procedure
all other flags set as they were left by real-mode procedure
stack unchanged
CF set on error
EAX = error code
01h not enough real-mode stack space
Note: this function is also supported by FlashTek X-32VM; under X-32VM, the
call will fail if ECX > 0000003Fh
SeeAlso: AX=250Dh,AX=2510h,AH=E1h"OS/286",INT 31/AX=0301h
----------21250F-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - CONVERT PROTECTED-MODE ADDRESS TO MS-DOS
AX = 250Fh
ES:EBX = 48-bit protected-mode address to convert
Return: CF clear if successful (address < 1MB)
ECX = 32-bit real-mode MS-DOS address
CF set on error (address >= 1MB)
ECX = linear address
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2510h
----------212510-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - CALL REAL-MODE PROCEDURE, REGISTERS
AX = 2510h
EBX = CS:IP of real-mode procedure to call
ECX = number of two-byte words to copy to protected-mode stack to
real-mode stack
DS:EDX -> pointer to parameter block (see below)
Return: CF clear if successful
all segment registers unchanged,
EDX unchanged
all other general registers contain values set by real-mode proc
all other flags are set as they were left by real-mode procedure
real-mode register values are returned in the parameter block
CF set on error
EAX = error code
01h not enough real-mode stack space
Note: unlike most of the preceding 25xxh functions, this one is not
supported by FlashTek X-32VM
SeeAlso: AX=250Eh,AX=250Fh
Format of parameter block:
Offset Size Description
00h WORD real-mode DS value
02h WORD real-mode ES value
04h WORD real-mode FS value
06h WORD real-mode GS value
08h DWORD real-mode EAX value
0Ch DWORD real-mode EBX value
10h DWORD real-mode ECX value
14h DWORD real-mode EDX value
----------212511-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - ISSUE REAL-MODE INTERRUPT
AX = 2511h
DS:EDX -> parameter block (see below)
Return: all segment registers unchanged
EDX unchanged
all other registers contain values set by the real-mode int handler
the flags are set as they were left by the real-mode interrupt handler
real-mode register values are returned in the parameter block
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2503h,AX=2505h,AX=250Eh,AH=E3h"OS/286",INT 31/AX=0300h
Format of parameter block:
Offset Size Description
00h WORD interrupt number
02h WORD real-mode DS value
04h WORD real-mode ES value
06h WORD real-mode FS value
08h WORD real-mode GS value
0Ah DWORD real-mode EAX value
0Eh DWORD real-mode EDX value
Note: all other real-mode values set from protected-mode registers
----------212512-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - LOAD PROGRAM FOR DEBUGGING
AX = 2512h
DS:EDX -> pointer to ASCIIZ program name
ES:EBX -> pointer to parameter block (see below)
ECX = size in bytes of LDT buffer
Return: CF clear if successful
EAX = number of segment descriptors in LDT
CF set on error
EAX = error code
02h file not found or path invalid
05h access denied
08h insufficient memory
0Ah environment invalid
0Bh invalid file format
80h LDT too small
Format of parameter block:
Offset Size Description
Input:
00h DWORD 32-bit offset of environment string
04h WORD segment of environment string
06h DWORD 32-bit offset of command-tail string
0Ah WORD segment of command-tail string
0Ch DWORD 32-bit offset of LDT buffer (size in ECX)
10h WORD segment of LDT buffer
Output:
12h WORD real-mode paragraph address of PSP (see also AH=26h)
14h WORD real/protected mode flag
0000h real mode
0001h protected mode
16h DWORD initial EIP value
1Ah WORD initial CS value
1Ch DWORD initial ESP value
20h WORD initial SS value
22h WORD initial DS value
24h WORD initial ES value
26h WORD initial FS value
28h WORD initial GS value
----------212513-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - ALIAS SEGMENT DESCRIPTOR
AX = 2513h
BX = segment selector of descriptor in GDT or LDT
CL = access-rights byte for alias descriptor
CH = use-type bit (USE16 or USE32) for alias descriptor
Return: CF clear if successful
AX = segment selector for created alias
CF set on error
EAX = error code
08h insufficient memory (can't grow LDT)
09h invalid segment selector in BX
----------212514-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - CHANGE SEGMENT ATTRIBUTES
AX = 2514h
BX = segment selector of descriptor in GDT or LDT
CL = new access-rights byte
CH = new use-type bit (USE16 or USE32)
Return: CF clear if successful
CF set on error
EAX = error code
09h invalid selector in BX
SeeAlso: AX=2515h,INT 31/AX=0009h
----------212515-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET SEGMENT ATTRIBUTES
AX = 2515h
BX = segment selector of descriptor in GDT or LDT
Return: CF clear if successful
CL = access-rights byte for segment
CH = use-type bit (USE16 or USE32)
ECX<16-31> destroyed
CF set on error
EAX = error code
09h invalid segment selector in BX
SeeAlso: AX=2514h
----------212516-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - FREE ALL MEMORY OWNED BY LDT
AX = 2516h
???
Return: ???
----------212517-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET INFO ON DOS DATA BUFFER
AX = 2517h
???
Return: ???
----------212518-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - SPECIFY HANDLER FOR MOVED SEGMENTS
AX = 2518h
???
Return: ???
----------212519-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - GET ADDITIONAL MEMORY ERROR INFO
AX = 2519h
Return: CF clear
EAX = error code
0000h no error
0001h out of physical memory
0002h out of swap space (unable to grow swap file)
0003h out of LDT entries and unable to grow LDT
0004h unable to change extended memory allocation mark
FFFFFFFFh paging disabled
Note: VMM is the Virtual Memory Manager option
----------21251A-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - LOCK PAGES IN MEMORY
AX = 251Ah
EDX = number of 4k pages to lock
if BL = 00h
ECX = linear address of first page to lock
if BL = 01h
ES:ECX -> pointer to first page to lock
Return: CF clear if successful
CF set on error
EAX = error code
08h insufficient memory
09h invalid address range
SeeAlso: AX=251Bh,AX=EB06h,INT 31/AX=0600h
----------21251B-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - UNLOCK PAGES
AX = 251Bh
EDX = number of pages to unlock
if BL = 00h
ECX = linear address of first page to unlock
if BL = 01h
ES:ECX -> pointer to first page to unlock
Return: CF clear if successful
CF set on error
EAX = error code
09h invalid address range
SeeAlso: AX=251Ah,AX=EB07h,INT 31/AX=0601h
----------21251D-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - READ PAGE-TABLE ENTRY
AX = 251Dh
???
Return: ???
SeeAlso: AX=251Eh,AX=EB00h,INT 31/AX=0506h
----------21251E-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - WRITE PAGE-TABLE ENTRY
AX = 251Eh
???
Return: ???
SeeAlso: AX=251Dh,INT 31/AX=0507h
----------21251F-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - EXHANGE TWO PAGE-TABLE ENTRIES
AX = 251Fh
???
Return: ???
SeeAlso: AX=251Dh,AX=251Eh
----------212520-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - GET MEMORY STATISTICS
AX = 2520h
DS:EDX -> pointer to buffer at least 100 bytes in size (see below)
BL = 0 (don't reset VM stats), 1 (reset VM stats)
Return: carry flag clear
Format of VM stats buffer:
Offset Size Description
00h DWORD VM status
0001h VM subsystem is present
0000h VM not present
04h DWORD "nconvpg" number of conventional memory pages available
08h DWORD "nbimpg" number of Compaq built-in memory pages available
0Ch DWORD "nextpg" total number of extended memory pages
10h DWORD "extlim" extender memory pages limit
14h DWORD "aphyspg" number of physical memory pages allocated to appl
18h DWORD "alockpg" number of locked pages owned by application
1Ch DWORD "sysphyspg" number physical memory pages allocated to system
20h DWORD "nfreepg" number of free physical pages; approx if EMS VCPI
24h DWORD linear address of beginning of application address space
28h DWORD linear address of end of application address space
2Ch DWORD number of seconds since last time VM stats were reset
30h DWORD number of page faults since last time
34h DWORD number of pages written to swap file since last time
38h DWORD number of reclaimed pages (page faults on swapped pages)
3Ch DWORD number of virtual pages allocated to the application
40h DWORD size in pages of swap file
44h DWORD number of system pages allocated with EMS calls
48h DWORD minimum number of conventional memory pages
4Ch DWORD maximum size in bytes to which swap file can be increased
50h DWORD "vmflags" bit 0 = 1 if page fault in progress
54h 16 BYTEs reserved for future expansion (set to zero)
----------212521-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - LIMIT PROGRAM'S EXTENDED MEMORY USAGE
AX = 2521h
EBX = max 4k pages of physical extended memory which program may use
Return: CF clear if successful
EBX = maximum limit in pages
ECX = minimum limit in pages
CF set on error
EAX = error code
08h insufficient memory or -nopage switch used
SeeAlso: AX=2522h
----------212522-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - SPECIFY ALTERNATE PAGE-FAULT HANDLER
AX = 2522h
???
Return: ???
SeeAlso: AX=2523h
----------212523-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - SPECIFY OUT-OF-SWAP-SPACE HANDLER
AX = 2523h
???
Return: ???
SeeAlso: AX=2522h
----------212524-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - INSTALL PAGE-REPLACEMENT HANDLERS
AX = 2524h
???
Return: ???
----------212525-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - LIMIT PROGRAM'S CONVENTIONAL MEM USAGE
AX = 2525h
EBX = limit in 4k pages of physical conventional memory which program
may use
Return: CF clear if successful
EBX = maximum limit in pages
ECX = minimum limit in pages
CF set on error
EAX = error code
08h insufficient memory or -nopage switch used
SeeAlso: AX=2521h
----------212526-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET CONFIGURATION INFORMATION
AX = 2526h
???
Return: ???
----------21252B-----------------------------
INT 21 - FlashTek X-32VM - VIRTUAL MEMORY MANAGEMENT - PAGE LOCKING
AX = 252Bh
BH = function
05h lock pages
06h unlock pages
BL = address type
00h linear address
ECX = linear start address of memory region
01h segmented address
ES:ECX -> start of memory region
EDX = size of memory region in bytes
Return: CF clear if successful
CF set on error
Note: if X-32 is not using virtual memory, this function always succeeds
----------212532-----------------------------
INT 21 - FlashTek X-32VM - GET EXCEPTION HANDLER VECTOR
AX = 2532h
CL = exception number (00h-0Fh)
Return: CF clear if successful
ES:EBX = CS:EIP of current exception handler
CF set on error (CL > 0Fh)
SeeAlso: AX=2533h
----------212533-----------------------------
INT 21 - FlashTek X-32VM - SET EXCEPTION HANDLER VECTOR
AX = 2533h
CL = exception number (00h-0Fh)
DS:EDX = CS:EIP of new exception handler
Return: CF clear if successful
CF set on error (CL > 0Fh)
SeeAlso: AX=2532h
----------2125C0-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - ALLOCATE MS-DOS MEMORY BLOCK
AX = 25C0h
BX = number of 16-byte paragraphs of MS-DOS memory requested
Return: CF clear if successful
AX = real-mode paragraph address of memory
CF set on error
AX = error code
07h MS-DOS memory control blocks destroyed
08h insufficient memory
BX = size in paragraphs of largest available memory block
SeeAlso: AX=25C1h,AX=25C2h
----------2125C1-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - RELEASE MS-DOS MEMORY BLOCK
AX = 25C1h
CX = real-mode paragraph address of memory block to free
Return: CF clear if successful
EAX destroyed
CF set on error
AX = error code
07h MS-DOS memory control blocks destroyed
09h invalid memory block address in CX
SeeAlso: AX=25C0h,AX=25C2h
----------2125C2-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - MODIFY MS-DOS MEMORY BLOCK
AX = 25C2h
BX = new requested block size in paragraphs
CX = real-mode paragraph address of memory block to modify
Return: CF clear if successful
EAX destroyed
CF set on error
AX = error code
07h MS-DOS memory control blocks destroyed
08h insufficient memory
09h invalid memory block address in CX
BX = size in paragraphs of largest available memory block
SeeAlso: AX=25C0h,AX=25C1h
----------2125C3-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - EXECUTE PROGRAM
AX = 25C3h
ES:EBX -> pointer to parameter block (see below)
DS:EDX -> pointer to ASCIIZ program filename
Return: CF clear if successful
all registers unchanged
CF set on error
EAX = error code
01h function code in AL is invalid ???
02h file not found or path invalid
05h access denied
08h insufficient memory to load program
0Ah environment invalid
0Bh invalid file format
Format of parameter block:
Offset Size Description
00h DWORD 32-bit offset of environment string
04h WORD segment selector of environment string
06h DWORD 32-bit offset of command-tail string
0Ah WORD segment selector of command-tail string
----------2126-------------------------------
INT 21 - DOS 1+ - CREATE NEW PROGRAM SEGMENT PREFIX
AH = 26h
DX = segment at which to create PSP (see below)
Notes: new PSP is updated with memory size information; INTs 22h, 23h, 24h
taken from interrupt vector table
(DOS 2+) DOS assumes that the caller's CS is the segment of the PSP to
copy
SeeAlso: AH=4Bh,AH=50h,AH=51h,AH=55h,AH=62h,AH=67h
Format of PSP:
Offset Size Description
00h 2 BYTEs INT 20 instruction for CP/M CALL 0 program termination
the CDh 20h here is often used as a signature for a valid PSP
02h WORD segment of first byte beyond memory allocated to program
04h BYTE unused filler
05h BYTE CP/M CALL 5 service request (FAR JMP to 000C0h)
BUG: (DOS 2+) PSPs created by INT 21/AH=4Bh point at 000BEh
06h WORD CP/M compatibility--size of first segment for .COM files
08h 2 BYTEs remainder of FAR JMP at 05h
0Ah DWORD stored INT 22 termination address
0Eh DWORD stored INT 23 control-Break handler address
12h DWORD DOS 1.1+ stored INT 24 critical error handler address
16h WORD segment of parent PSP
18h 20 BYTEs DOS 2+ Job File Table, one byte per file handle, FFh = closed
2Ch WORD DOS 2+ segment of environment for process
2Eh DWORD DOS 2+ process's SS:SP on entry to last INT 21 call
32h WORD DOS 3+ number of entries in JFT (default 20)
34h DWORD DOS 3+ pointer to JFT (default PSP:0018h)
38h DWORD DOS 3+ pointer to previous PSP (default FFFFFFFFh in 3.x)
used by SHARE in DOS 3.3
3Ch 4 BYTEs unused by DOS versions <= 5.00
reportedly used by Novell NetWare shell 3.x
40h 2 BYTEs DOS 5.0 version to return on INT 21/AH=30h
42h 6 BYTEs unused by DOS versions <= 5.00
48h BYTE (MSWindows3) bit 0 set if non-Windows application (WINOLDAP)
49h 7 BYTEs unused by DOS versions <= 5.00
50h 3 BYTEs DOS 2+ service request (INT 21/RETF instructions)
53h 9 BYTEs unused in DOS versions <= 5.00
5Ch 16 BYTEs first default FCB, filled in from first commandline argument
overwrites second FCB if opened
6Ch 16 BYTEs second default FCB, filled in from second commandline argument
overwrites beginning of commandline if opened
7Ch 4 BYTEs unused
80h 128 BYTEs commandline / default DTA
command tail is BYTE for length of tail, N BYTEs for the tail,
followed by a BYTE containing 0Dh
Notes: in DOS versions 3.0 and up, the limit on simultaneously open files may
be increased by allocating memory for a new open file table, filling
it with FFh, copying the first 20 bytes from the default table, and
adjusting the pointer and count at 34h and 32h. However, DOS
versions through at least 3.30 will only copy the first 20 file
handles into a child PSP (including the one created on EXEC).
network redirectors based on the original MS-Net implementation use
values of 80h-FEh in the open file table to indicate remote files;
Novell NetWare reportedly also uses values of 80h-FEh
MSDOS 5.00 incorrectly fills the FCB fields when loading a program
high; the first FCB is empty and the second contains the first
parameter
some DOS extenders place protected-mode values in various PSP fields
such as the "parent" field, which can confuse PSP walkers. Always
check either for the CDh 20h signature or that the suspected PSP is
at the beginning of a memory block which owns itself (the preceding
paragraph should be a valid MCB with "owner" the same as the
suspected PSP).
Format of environment block:
Offset Size Description
00h N BYTEs first environment variable, ASCIZ string of form "var=value"
N BYTEs second environment variable, ASCIZ string
...
N BYTEs last environment variable, ASCIZ string of form "var=value"
BYTE 00h
---DOS 3+---
WORD number of strings following environment (normally 1)
N BYTEs ASCIZ full pathname of program owning this environment
other strings may follow
----------2127-------------------------------
INT 21 - DOS 1+ - RANDOM BLOCK READ FROM FCB FILE
AH = 27h
CX = number of records to read
DS:DX -> opened FCB (see AH=0Fh)
Return: AL = status
00h successful, all records read
01h end of file, no data read
02h segment wrap in DTA, no data read
03h end of file, partial read
[DTA] = records read from file
CX = number of records read (return AL = 00h or 03h)
Notes: read begins at current file position as specified in FCB; the file
position is updated after reading
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=21h,AH=28h,AH=3Fh
----------2128-------------------------------
INT 21 - DOS 1+ - RANDOM BLOCK WRITE TO FCB FILE
AH = 28h
CX = number of records to write
DS:DX -> opened FCB (see AH=0Fh)
[DTA] = records to write
Return: AL = status
00h successful
01h disk full or file read-only
02h segment wrap in DTA
CX = number of records written
Notes: write begins at current file position as specified in FCB; the file
position is updated after writing
if CX = 0000h on entry, no data is written; instead the file size is
adjusted to be the same as the file position specified by the random
record and record size fields of the FCB
if the data to be written is less than a disk sector, it is copied into
a DOS disk buffer, to be written out to disk at a later time
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=22h,AH=27h,AH=40h,AH=59h
----------2129-------------------------------
INT 21 - DOS 1+ - PARSE FILENAME INTO FCB
AH = 29h
AL = parsing options
bit 0: skip leading separators
bit 1: use existing drive number in FCB if no drive is specified,
instead of setting field to zero
bit 2: use existing filename in FCB if no base name is specified,
instead of filling field with blanks
bit 3: use existing extension in FCB if no extension is specified,
instead of filling field with blanks
bits 4-7: reserved (0)
DS:SI -> filename string (both '*' and '?' wildcards OK)
ES:DI -> buffer for unopened FCB
Return: AL = result code
00h successful parse, no wildcards encountered
01h successful parse, wildcards present
FFh failed (invalid drive specifier)
DS:SI -> first unparsed character
ES:DI buffer filled with unopened FCB (see AH=0Fh)
Notes: asterisks expanded to question marks in the FCB
all processing stops when a filename terminator is encountered
cannot be used with filespecs which include a path (DOS 2+)
SeeAlso: AH=0Fh,AH=16h,AH=26h
----------212A-------------------------------
INT 21 - DOS 1+ - GET SYSTEM DATE
AH = 2Ah
Return: CX = year (1980-2099)
DH = month
DL = day
---DOS 1.10+---
AL = day of week (00h=Sunday)
SeeAlso: AH=2Bh"DOS",AH=2Ch,AH=E7h,INT 1A/AH=04h,INT 2F/AX=120Dh
----------212B-------------------------------
INT 21 - DOS 1+ - SET SYSTEM DATE
AH = 2Bh
CX = year (1980-2099)
DH = month
DL = day
Return: AL = status
00h successful
FFh invalid date, system date unchanged
Note: DOS 3.3+ also sets CMOS clock
SeeAlso: AH=2Ah,AH=2Dh,INT 1A/AH=05h
----------212B--CX4149-----------------------
INT 21 - AI Architects - ??? - INSTALLATION CHECK
AH = 2Bh
CX = 4149h ('AI')
DX = 413Fh ('A?')
Return: AL <> FFh if installed
Note: Borland's TKERNEL makes this call
----------212B--CX4358-----------------------
INT 21 - PC Tools v5.x PC-Cache - INSTALLATION CHECK
AH = 2Bh
CX = 4358h ('CX')
Return: AL = FFh if PC-Cache not installed
AL = 00h if installed
CX = 6378h ('cx')
BX = ???
DX = ???
SeeAlso: INT 16/AX=FFA5h/CX=1111h
----------212B--CX4445-----------------------
INT 21 - DESQview - INSTALLATION CHECK
AH = 2Bh
CX = 4445h ('DE')
DX = 5351h ('SQ')
AL = subfunction (DV v2.00+)
01h get version
Return: BX = version (BH = major, BL = minor)
Note: early copies of v2.00 return 0002h
02h get shadow buffer info, and start shadowing
Return: BH = rows in shadow buffer
BL = columns in shadow buffer
DX = segment of shadow buffer
04h get shadow buffer info
Return: BH = rows in shadow buffer
BL = columns in shadow buffer
DX = segment of shadow buffer
05h stop shadowing
Return: AL = FFh if DESQview not installed
Notes: in DESQview v1.x, there were no subfunctions; this call only identified
whether or not DESQview was loaded. DESQview v2.52 performs function
01h for all subfunction requests 0Ch and higher and appears to ignore
all lower-numbered functions not listed here.
DESQview versions 2.5x are part of DESQview/X v1.0x.
BUG: subfunction 05h does not appear to work correctly in DESQview 2.52
SeeAlso: INT 10/AH=FEh,INT 10/AH=FFh,INT 15/AX=1024h,INT 15/AX=DE30h
----------212B--CX454C-----------------------
INT 21 - ELRES v1.1 - INSTALLATION CHECK
AH = 2Bh
CX = 454Ch ('EL')
DX = 5253h ('RS')
Return: ES:BX -> ELRES history structure (see below)
DX = DABEh (signature, DAve BEnnett)
Note: ELRES is an MSDOS return code (errorlevel) recorder by David H. Bennett
which stores recent errorlevel values, allows them to be retrieved
for use in batch files, and can place them in an environment variable
SeeAlso: AH=4Bh"ELRES",AH=4Dh
Format of ELRES history structure:
Offset Size Description
00h WORD number of return codes which can be stored by following buffer
02h WORD current position in buffer (treated as a ring)
04h N BYTEs ELRES buffer
----------212B01CX5441-----------------------
INT 21 - TAME v2.10+ - INSTALLATION CHECK
AX = 2B01h
CX = 5441h ('TA')
DX = 4D45h ('ME')
---v2.60---
BH = ???
00h skip ???, else do
Return: AL = 02h if installed
ES:DX -> data area in TAME-RES (see below)
Note: TAME is a shareware program by David G. Thomas which gives up CPU time
to other partitions under a multitasker when the current partition's
program incessantly polls the keyboard or system time
Format of TAME 2.10-2.20 data area:
Offset Size Description
00h BYTE data structure minor version number (01h in TAME 2.20)
01h BYTE data structure major version number (07h in TAME 2.20)
02h DWORD number of task switches
06h DWORD number of keyboard polls
0Ah DWORD number of time polls
0Eh DWORD number of times DESQview told program runs only in foreground
12h DWORD original INT 10h
16h DWORD original INT 14h
1Ah DWORD original INT 15h
1Eh DWORD original INT 16h
22h DWORD original INT 17h
26h DWORD original INT 21h
2Ah DWORD original INT 28h
2Eh WORD offset of TAME INT 10h handler
30h WORD offset of TAME INT 14h handler
32h WORD offset of TAME INT 15h handler
34h WORD offset of TAME INT 16h handler
36h WORD offset of TAME INT 17h handler
38h WORD offset of TAME INT 21h handler
3Ah WORD offset of TAME INT 28h handler
3Ch WORD X in /max:X,Y or /freq:X,Y
3Eh WORD Y in /max:X,Y or /freq:X,Y
40h WORD number of polls remaining before next task switch
42h WORD /KEYIDLE value
44h BYTE flags for interrupts already grabbed by TAME
bit 0: INT 10h
1: INT 14h
2: INT 15h
3: INT 16h
4: INT 17h
5: INT 21h
6: INT 28h
45h BYTE flags for interrupts which may be acted on (same bits as above)
46h BYTE TAME enabled (01h) or disabled (00h)
47h BYTE /TIMEPOLL (01h) or /NOTIMEPOLL (00h)
48h BYTE /NOTIMER (01h) or /TIMER (00h)
49h BYTE window or task number for this task
4Ah BYTE multitasker type ???
01h DESQview
02h DoubleDOS
03h TopView
???
4Bh BYTE type of task switching selected
bit 0: DESQview???
1: DoubleDOS???
2: TopView???
3: KeySwitch
4: HLT instruction
4Ch BYTE ???
4Dh BYTE flags
bit 1: /FREQ instead of /MAX
4Eh BYTE /FG: value
4Fh BYTE task switches left until next FGONLY DESQview API call
50h BYTE ???
Format of TAME 2.30 data area:
Offset Size Description
00h BYTE data structure minor version number (02h in TAME 2.30)
01h BYTE data structure major version number (0Ah in TAME 2.30)
02h DWORD number of task switches
06h DWORD number of keyboard polls
0Ah DWORD number of time polls
0Eh DWORD number of times DESQview told program runs only in foreground
12h DWORD time of last /CLEAR or TAME-RES load
16h DWORD time yielded
1Ah DWORD time spent polling
1Eh DWORD time spent waiting on key input with INT 16/AH=01h,11h
22h DWORD original INT 10h
26h DWORD original INT 14h
2Ah DWORD original INT 15h
2Eh DWORD original INT 16h
32h DWORD original INT 17h
36h DWORD original INT 21h
3Ah DWORD original INT 28h
3Eh WORD offset of TAME INT 10h handler
40h WORD offset of TAME INT 14h handler
42h WORD offset of TAME INT 15h handler
44h WORD offset of TAME INT 16h handler
46h WORD offset of TAME INT 17h handler
48h WORD offset of TAME INT 21h handler
4Ah WORD offset of TAME INT 28h handler
4Ch WORD X in /max:X,Y or /freq:X,Y
4Eh WORD Y in /max:X,Y or /freq:X,Y
50h WORD number of polls remaining before next task switch
52h WORD /KEYIDLE value
54h WORD /FG: value
56h WORD task switches left until next FGONLY DESQview API call
58h WORD multitasker version
5Ah WORD virtual screen segment
5Ch BYTE flags for interrupts already grabbed by TAME
bit 0: INT 10h
1: INT 14h
2: INT 15h
3: INT 16h
4: INT 17h
5: INT 21h
6: INT 28h
5Dh BYTE flags for interrupts which may be acted on (same bits as above)
5Eh BYTE window or task number for this task
5Fh BYTE multitasker type
01h DESQview
02h DoubleDOS
03h TopView
04h OmniView
05h VM/386
60h BYTE type of task switching selected (bit flags)
bit 0: DESQview
1: DoubleDOS
2: TopView
3: OmniView
4: KeySwitch
5: HLT instruction
61h BYTE watch_DOS
62h BYTE bit flags
bit 0: TAME enabled
1: /FREQ instead of /MAX (counts in 3Ch and 3Eh per tick)
2: /TIMEPOLL
3: /KEYPOLL
4: inhibit timer
5: enable status monitoring
63h BYTE old status
64h WORD signature DA34h
Format of TAME 2.60 data area:
Offset Size Description
00h BYTE data structure minor version number (02h in TAME 2.60)
01h BYTE data structure major version number (0Bh in TAME 2.60)
02h DWORD number of task switches
06h DWORD number of keyboard polls
0Ah DWORD number of time polls
0Eh DWORD number of times DESQview told program runs only in foreground
12h DWORD time of last /CLEAR or TAME-RES load
16h DWORD time yielded
1Ah DWORD time spent polling
1Eh DWORD time spent waiting on key input with INT 16/AH=01h,11h
22h 4 BYTEs ???
26h DWORD original INT 10h
2Ah DWORD original INT 14h
2Eh DWORD original INT 15h
32h DWORD original INT 16h
36h DWORD original INT 17h
3Ah DWORD original INT 21h
3Eh DWORD original INT 28h
42h WORD offset of TAME INT 10h handler
44h WORD offset of TAME INT 14h handler
46h WORD offset of TAME INT 15h handler
48h WORD offset of TAME INT 16h handler
4Ah WORD offset of TAME INT 17h handler
4Ch WORD offset of TAME INT 21h handler
4Eh WORD offset of TAME INT 28h handler
50h WORD X in /max:X,Y or /freq:X,Y
52h WORD Y in /max:X,Y or /freq:X,Y
54h WORD number of polls remaining before next task switch
56h WORD /KEYIDLE value
58h 4 BYTEs ???
5Ch WORD X in /boost:X,Y
5Eh WORD Y in /boost:X,Y
60h WORD /FG: value
62h WORD task switches left until next FGONLY DESQview API call
64h WORD multitasker version ???
66h WORD virtual screen segment
68h BYTE flags for interrupts already grabbed by TAME
bit 0: INT 10h
1: INT 14h
2: INT 15h
3: INT 16h
4: INT 17h
5: INT 21h
6: INT 28h
69h BYTE flags for interrupts which may be acted on (same bits as above)
6Ah BYTE window or task number for this task
6Bh BYTE multitasker type
01h DESQview
02h DoubleDOS
03h TopView
04h OmniView
05h VM/386
6Ch BYTE type of task switching selected (bit flags)
bit 0: DESQview
1: DoubleDOS
2: TopView
3: OmniView
4: KeySwitch
5: HLT instruction
6Dh BYTE watch_DOS
6Eh BYTE bit flags
bit 0: TAME enabled
1: /FREQ instead of /MAX (counts in 50h and 52h per tick)
2: /TIMEPOLL
3: /KEYPOLL
4: inhibit timer
5: enable status monitoring
6Fh BYTE old status
70h WORD signature DA34h
----------212B44BX4D41-----------------------
INT 21 - pcANYWHERE IV/LAN - INSTALLATION CHECK
AX = 2B44h ('D')
BX = 4D41h ('MA')
CX = 7063h ('pc')
DX = 4157h ('AW')
Return: AX = 4F4Bh ('OK') if large host resident
= 6F6Bh ('ok') if small host resident
CX:DX -> API entry point
SeeAlso: INT 16/AH=79h
Call API entry point with:
AX = 0000h get pcANYWHERE IV version
DS:SI -> BYTE buffer for host type code
Return: AH = version number
AL = revision number
DS:DI buffer byte filled with
00h full-featured host
01h limited-feature LAN host
other API may not be supported
AX = 0001h initialize operation
DS:SI -> initialization request structure (see below)
Return: AX = function status (see below)
AX = 0002h get status
Return: AH = current operating mode (see init req structure below)
AL = current connection status
bit 0: a physical connection is active
bit 1: remove screen updating is active
bit 2: connection checking is active
bit 3: hot key detection is active
bit 4: background file transfer is active
AX = 0003h suspend remote screen updates
Return: AX = function status (see below)
AX = 0004h resume screen updates
Return: AX = function status (see below)
AX = 0005h end current remote access session
DS:SI -> termination request structure (see below)
Return: AX = function status (see below)
AX = 0006h remove pcANYWHERE IV from memory
Return: AX = status
0000h successful
FFD2h unable to release allocated memory
FFD1h unable to release interrupt vectors
AX = 8000h read data from communications channel
DS:BX -> buffer
CX = buffer size
Return: AX >= number of characters read/available
AX < 0 on error
AX = 8001h write data to communications channel
DS:BX -> buffer
CX = buffer size
Return: AX >= number of characters written
AX < 0 on error
AX = 8002h get connection status
Return: AX = status
> 0000h if connection active
= 0000h if connection lost
< 0000h on error
Format of initialization request structure:
Offset Size Description
00h BYTE operating mode
00h wait for a call
01h hot key activates
02h incoming call activates
03h initiate a call
01h 3 BYTEs user ID to append to config file names
04h WORD DS-relative pointer to path for config files
06h WORD DS-relative pointer to path for program files
Format of termination request structure:
Offset Size Description
00h BYTE operating mode after termination
00h wait for a call
01h hot key activates
02h incoming call activates
80h use current mode
FFh remove from memory
Values for function status:
0000h function completed successfully
FFF2h unable to establish a connection when operating mode is
"Initiate a call"
FFF3h modem configuration is invalid (corrupt config)
FFF4h modem initialization failed (no modem response)
FFF5h the communications device could not be initialized
FFF6h the host operator aborted the function
FFF7h the communications driver type specified in the configuration file is
different than the one loaded when pcANYWHERE IV was initially started
FFF9h the configuration file is invalid
FFFAh the configuration file could not be found
FFFBh no session is active
FFFCh a remote access session is active
FFFDh the specified operating mode is invalid
----------212C-------------------------------
INT 21 - DOS 1+ - GET SYSTEM TIME
AH = 2Ch
Return: CH = hour
CL = minute
DH = second
DL = 1/100 seconds
Note: on most systems, the resolution of the system clock is about 5/100sec,
so returned times generally do not increment by 1
on some systems, DL may always return 00h
SeeAlso: AH=2Ah,AH=2Dh,AH=E7h,INT 1A/AH=00h,INT 1A/AH=02h,INT 1A/AH=FEh
SeeAlso: INT 2F/AX=120Dh
----------212D-------------------------------
INT 21 - DOS 1+ - SET SYSTEM TIME
AH = 2Dh
CH = hour
CL = minute
DH = second
DL = 1/100 seconds
Return: AL = result
00h successful
FFh invalid time, system time unchanged
Note: DOS 3.3+ also sets CMOS clock
SeeAlso: AH=2Bh"DOS",AH=2Ch,INT 1A/AH=01h,INT 1A/AH=03h,INT 1A/AH=FFh"AT&T"
----------212E--DL00-------------------------
INT 21 - DOS 1+ - SET VERIFY FLAG
AH = 2Eh
DL = 00h (DOS 1.x/2.x only)
AL = new state of verify flag
00h off
01h on
Notes: default state at system boot is OFF
when ON, all disk writes are verified provided the device driver
supports read-after-write verification
SeeAlso: AH=54h
----------212F-------------------------------
INT 21 - DOS 2+ - GET DISK TRANSFER AREA ADDRESS
AH = 2Fh
Return: ES:BX -> current DTA
Note: under the FlashTek X-32 DOS extender, the pointer is in ES:EBX
SeeAlso: AH=1Ah
----------2130-------------------------------
INT 21 - DOS 2+ - GET DOS VERSION
AH = 30h
---DOS 5.0---
AL = what to return in BH
00h OEM number (as for DOS 2.0-4.0x)
01h version flag
Return: AL = major version number (00h if DOS 1.x)
AH = minor version number
BL:CX = 24-bit user serial number (most versions do not use this)
---if DOS <5 or AL=00h---
BH = OEM number
00h IBM
05h Zenith
16h DEC
23h Olivetti
29h Toshiba
4Dh Hewlett-Packard
99h STARLITE architecture (OEM DOS, NETWORK DOS, SMP DOS)
FFh Microsoft, Phoenix
---if DOS 5.0 and AL=01h---
BH = version flag
08h DOS is in ROM
10h DOS is in HMA
Notes: the OS/2 v1.x Compatibility Box returns major version 0Ah (10)
the OS/2 v2.x Compatibility Box returns major version 14h (20)
the Windows/NT DOS box returns major version 1Eh (30)
DOS 4.01 and 4.02 identify themselves as version 4.00; use
INT 21/AH=87h to distinguish between the original European MSDOS 4.00
and the later PCDOS 4.0x and MSDOS 4.0x
generic MSDOS 3.30, Compaq MSDOS 3.31, and others identify themselves
as PC-DOS by returning OEM number 00h
the version returned under DOS 4.0x may be modified by entries in
the special program list (see AH=52h)
the version returned under DOS 5.0 may be modified by SETVER; use
AX=3306h to get the true version number
SeeAlso: AX=3000h/BX=3000h,AX=3306h,AX=4452h,AH=87h,INT 15/AX=4900h
SeeAlso: INT 2F/AX=122Fh,INT 2F/AX=E002h
----------2130-------------------------------
INT 21 - Phar Lap 386/DOS-Extender, Intel Code Builder - INSTALLATION CHECK
AH = 30h
EAX = 00003000h
EBX = 50484152h ("PHAR")
Return: AL = major DOS version
AH = minor DOS version
EAX bits 31-16 = 4458h ('DX') if 386/DOS-extender installed
BL = ASCII major version number
EAX bits 31-16 = 4243h ('BC') if Intel Code Builder installed
EDX = address of GDA
SeeAlso: AX=2501h,AX=FF00h,INT 2F/AX=F100h
----------2130--DXABCD-----------------------
INT 21 - VIRUS - "Possessed" - INSTALLATION CHECK
AH = 30h
DX = ABCDh
Return: DX = DCBAh if installed
SeeAlso: AX=0D20h,AX=30F1h
----------213000-----------------------------
INT 21 - Btrieve Multi-User - INSTALLATION CHECK
AX = 3000h
Return: AL >= 03h if INT 2F handler installed
SeeAlso: INT 2F/AX=AB00h,INT 7B"Btrieve",INT 7F/AX=0200h
----------213000BX1234-----------------------
INT 21 - CTask 2.0+ - INSTALLATION CHECK
AX = 3000h
BX = 1234h
DS:DX -> 8-byte version string (DX < FFF0h) "CTask21",00h for v2.1-2.2
Return: AL = DOS major version
AH = DOS minor version
CX:BX -> Ctask global data block
Notes: if first eight bytes of returned data block equal eight bytes passed
in, CTask is resident
CTask is a multitasking kernel for C written by Thomas Wagner
----------213000BX3000-----------------------
INT 21 - PC-MOS/386 v3.0 - INSTALLATION CHECK/GET VERSION
AX = 3000h
BX = 3000h
CX = DX = 3000h
Return: AX = PC-MOS version
Program: PC-MOS/386 is a multitasking/multiuser MSDOS-compatible operating
system by Software Links, Inc.
SeeAlso: AH=30h,INT 38/AH=02h,INT 38/AH=10h
----------2130F1-----------------------------
INT 21 - VIRUS - "Dutch-555"/"Quit 1992" - INSTALLATION CHECK
AX = 30F1h
Return: AL = 00h if resident
SeeAlso: AH=30h/DX=ABCDh,AX=330Fh
----------2131-------------------------------
INT 21 - DOS 2+ - TERMINATE AND STAY RESIDENT
AH = 31h
AL = return code
DX = number of paragraphs to keep resident
Return: never
Notes: the value in DX only affects the memory block containing the PSP;
additional memory allocated via AH=48h is not affected
the minimum number of paragraphs which will remain resident is 11h
for DOS 2.x and 06h for DOS 3+
most TSRs can save some memory by releasing their environment block
before terminating (see AH=26h,AH=49h)
SeeAlso: AH=00h,AH=4Ch,AH=4Dh,INT 20,INT 22,INT 27
----------2132-------------------------------
INT 21 - DOS 2+ - GET DOS DRIVE PARAMETER BLOCK FOR SPECIFIC DRIVE
AH = 32h
DL = drive number (00h = default, 01h = A:, etc)
Return: AL = status
00h successful
DS:BX -> Drive Parameter Block (DPB) for specified drive
FFh invalid or network drive
Notes: the OS/2 compatibility box supports the DOS 3.3 version of this call
except for the DWORD at offset 12h
this call updates the DPB by reading the disk; the DPB may be accessed
via the DOS list of lists (see AH=52h) if disk access is not
desirable.
undocumented prior to the release of DOS 5.0; only the DOS 4+ version
of the DPB has been documented, however
SeeAlso: AH=1Fh,AH=52h
Format of DOS Drive Parameter Block:
Offset Size Description
00h BYTE drive number (00h = A:, 01h = B:, etc)
01h BYTE unit number within device driver
02h WORD bytes per sector
04h BYTE highest sector number within a cluster
05h BYTE shift count to convert clusters into sectors
06h WORD number of reserved sectors at beginning of drive
08h BYTE number of FATs
09h WORD number of root directory entries
0Bh WORD number of first sector containing user data
0Dh WORD highest cluster number (number of data clusters + 1)
16-bit FAT if greater than 0FF6h, else 12-bit FAT
0Fh BYTE number of sectors per FAT
10h WORD sector number of first directory sector
12h DWORD address of device driver header
16h BYTE media ID byte
17h BYTE 00h if disk accessed, FFh if not
18h DWORD pointer to next DPB
---DOS 2.x---
1Ch WORD cluster containing start of current directory, 0000h=root,
FFFFh = unknown
1Eh 64 BYTEs ASCIZ pathname of current directory for drive
---DOS 3.x---
1Ch WORD cluster at which to start search for free space when writing
1Eh WORD number of free clusters on drive, FFFFh = unknown
---DOS 4.0-5.0---
0Fh WORD number of sectors per FAT
11h WORD sector number of first directory sector
13h DWORD address of device driver header
17h BYTE media ID byte
18h BYTE 00h if disk accessed, FFh if not
19h DWORD pointer to next DPB
1Dh WORD cluster at which to start search for free space when writing,
usually the last cluster allocated
1Fh WORD number of free clusters on drive, FFFFh = unknown
----------2133-------------------------------
INT 21 - DOS 2+ - EXTENDED BREAK CHECKING
AH = 33h
AL = subfunction
00h get current extended break state
Return: DL = current state, 00h = off, 01h = on
01h set state of extended ^C/^Break checking
DL = 00h off, check only on character I/O functions
01h on, check on all DOS functions
Note: under DOS 3.1+, this function does not use any of the DOS-internal and
may thus be called at any time
SeeAlso: AX=3302h
----------213302-----------------------------
INT 21 - DOS 3.x+ internal - GET AND SET EXTENDED CONTROL-BREAK CHECKING STATE
AX = 3302h
DL = new state
00h for OFF or 01h for ON
Return: DL = old state of extended BREAK checking
Note: this function does not use any of the DOS-internal stacks and may thus
be called at any time; one possible use is modifying Control-Break
checking from within an interrupt handler or TSR
SeeAlso: AH=33h
----------213305-----------------------------
INT 21 - DOS 4+ - GET BOOT DRIVE
AX = 3305h
Return: DL = boot drive (1=A:,...)
Notes: fully reentrant
NEC 9800-series PCs always call the boot drive A: and assign the other
drive letters sequentially to the other drives in the system
----------213306-----------------------------
INT 21 - DOS 5.0 - GET TRUE VERSION NUMBER
AX = 3306h
Return: BL = major version
BH = minor version
DL = revision (bits 2-0, all others 0)
DH = version flags
bit 3: DOS is in ROM
bit 4: DOS in in HMA
Notes: this function always returns the true version number, unlike AH=30h,
whose return value may be changed with SETVER
because of the conflict from the CBIS PowerLAN redirector (see next
entry), programs should check whether BH is less than 100 (64h)
and BL is at least 5 before accepting the returned BX as the true
version number; however, even this is not entirely reliable when
that redirector is loaded
fully reentrant
BUG: DR-DOS 5.0 and 6.0 return CF set/AX=0001h for INT 21/AH=33h
subfunctions other than 00h-02h and 05h, while MS-DOS returns AL=FFh
for invalid subfunctions
SeeAlso: AH=30h,INT 2F/AX=112Fh
----------213306-----------------------------
INT 21 - CBIS POWERLAN - NETWORK REDIRECTOR - ???
AX = 3306h
Return: AX = 3306h
BL = ??? (usually 00h)
BH = ??? (usually 00h or FFh)
Note: unknown function, is in conflict with DOS 5.0 version call
SeeAlso: AX=3306h"DOS"
----------21330F-----------------------------
INT 21 - VIRUS - "Burghofer" - INSTALLATION CHECK
AX = 330Fh
Return: AL = 0Fh if resident (DOS returns AL=FFh)
SeeAlso: AX=30F1h,AX=33E0h
----------2133E0-----------------------------
INT 21 - VIRUS - "Oropax" - INSTALLATION CHECK
AX = 33E0h
Return: AL = E0h if resident (DOS returns AL=FFh)
SeeAlso: AX=330Fh,AX=357Fh
----------2134-------------------------------
INT 21 - DOS 2+ - GET ADDRESS OF INDOS FLAG
AH = 34h
Return: ES:BX -> one-byte InDOS flag
Notes: the value of InDOS is incremented whenever an INT 21 function begins
and decremented whenever one completes
during an INT 28 call, it is safe to call some INT 21 functions even
though InDOS may be 01h instead of zero
InDOS alone is not sufficient for determining when it is safe to
enter DOS, as the critical error handling decrements InDOS and
increments the critical error flag for the duration of the critical
error. Thus, it is possible for InDOS to be zero even if DOS is
busy.
the critical error flag is the byte immediately following InDOS in
DOS 2.x, and the byte BEFORE the InDOS flag in DOS 3+ (except COMPAQ
DOS 3.0, where the critical error flag is located 1AAh bytes BEFORE
the critical section flag)
For DOS 3.1+, an undocumented call exists to get the address of the
critical error flag (see AX=5D06h)
this function was undocumented prior to the release of DOS 5.0.
SeeAlso: AX=5D06h,AX=5D0Bh,INT 28
----------2135-------------------------------
INT 21 - DOS 2+ - GET INTERRUPT VECTOR
AH = 35h
AL = interrupt number
Return: ES:BX -> current interrupt handler
SeeAlso: AH=25h,AX=2503h
----------213501-----------------------------
INT 21 P - FlashTek X-32VM - ALLOCATE PROTECTED-MODE SELECTOR
AX = 3501h
Return: CF clear if successful
BX = new selector
CF set on error (no more selectors available)
Note: the new selector will be an expand-up read/write data selector with
undefined base and limit
SeeAlso: AX=3502h,INT 31/AX=0000h
----------213502-----------------------------
INT 21 P - FlashTek X-32VM - DEALLOCATE PROTECTED-MODE SELECTOR
AX = 3502h
BX = selector
Return: CF clear if successful
CF set on error (invalid selector)
Note: only selectors allocated via AX=3501h should be deallocated
SeeAlso: AX=3501h,INT 31/AX=0001h
----------213503-----------------------------
INT 21 P - FlashTek X-32VM - SET SELECTOR BASE ADDRESS
AX = 3503h
BX = selector
ECX = base address
Return: CF clear if successful
CF set on error (invalid selector)
Note: there are probably additional 35xxh functions, but the message
containing the FlashTek calls was truncated in transit and the
remaining information did not arrive prior to release
SeeAlso: INT 31/AX=0007h
----------21357F-----------------------------
INT 21 - VIRUS - "Agiplan"/"Month 4-6" - INSTALLATION CHECK
AX = 357Fh
Return: DX = FFFFh if installed
SeeAlso: AX=33E0h,AX=3DFFh
----------2136-------------------------------
INT 21 - DOS 2+ - GET FREE DISK SPACE
AH = 36h
DL = drive number (00h = default, 01h = A:, etc)
Return: AX = FFFFh if invalid drive
else
AX = sectors per cluster
BX = number of free clusters
CX = bytes per sector
DX = total clusters on drive
Notes: free space on drive in bytes is AX * BX * CX
total space on drive in bytes is AX * CX * DX
"lost clusters" are considered to be in use
according to Dave Williams' MSDOS reference, the value in DX is
incorrect for non-default drives after ASSIGN is run
SeeAlso: AH=1Bh,AH=1Ch
----------213700-----------------------------
INT 21 - DOS 2+ - "SWITCHAR" - GET SWITCH CHARACTER
AX = 3700h
Return: AL = status
00h successful
DL = current switch character
FFh unsupported subfunction
Desc: Determine the character which is used to introduce command switches.
This setting is ignored by DOS commands in version 4.0 and higher,
but is honored by many third-party programs.
Notes: documented in some OEM versions of some releases of DOS
supported by OS/2 compatibility box
always returns DL=2Fh for DOS 5.0
SeeAlso: AX=3701h
----------213701-----------------------------
INT 21 - DOS 2+ - "SWITCHAR" - SET SWITCH CHARACTER
AX = 3701h
DL = new switch character
Return: AL = status
00h successful
FFh unsupported subfunction
Notes: documented in some OEM versions of some releases of DOS
supported by OS/2 compatibility box
ignored by DOS 5.0
SeeAlso: AX=3700h
----------2137-------------------------------
INT 21 - DOS 2.x and 3.3+ only - "AVAILDEV" - SPECIFY \DEV\ PREFIX USE
AH = 37h
AL = subfunction
02h get availdev flag
Return: DL = 00h \DEV\ must precede character device names
= nonzero \DEV\ is optional
03h set availdev flag
DL = 00h \DEV\ is mandatory
= nonzero \DEV\ is optional
Return: AL = status
00h successful
FFh unsupported subfunction
Notes: all versions of DOS from 2.00 allow \DEV\ to be prepended to device
names without generating an error even if the directory \DEV does
not actually exist (other paths generate an error if they do not
exist).
although DOS 3.3+ accepts these calls, they have no effect, and
AL=02h always returns DL=FFh
----------2138-------------------------------
INT 21 - DOS 2+ - GET COUNTRY-SPECIFIC INFORMATION
AH = 38h
--DOS 2.x--
AL = 00h get current-country info
DS:DX -> buffer for returned info (see below)
Return: CF set on error
AX = error code (02h)
CF clear if successful
AX = country code (MSDOS 2.11 only)
buffer at DS:DX filled
--DOS 3+--
AL = 00h for current country
AL = 01h thru 0FEh for specific country with code <255
AL = 0FFh for specific country with code >= 255
BX = 16-bit country code
DS:DX -> buffer for returned info (see below)
Return: CF set on error
AX = error code (02h)
CF clear if successful
BX = country code
DS:DX buffer filled
SeeAlso: AH=65h,INT 10/AX=5001h,INT 2F/AX=110Ch,INT 2F/AX=1404h
Format of PCDOS 2.x country info:
Offset Size Description
00h WORD date format 0 = USA mm dd yy
1 = Europe dd mm yy
2 = Japan yy mm dd
02h BYTE currency symbol
03h BYTE 00h
04h BYTE thousands separator char
05h BYTE 00h
06h BYTE decimal separator char
07h BYTE 00h
08h 24 BYTEs reserved
Format of MSDOS 2.x,DOS 3+ country info:
Offset Size Description
00h WORD date format (see above)
02h 5 BYTEs ASCIZ currency symbol string
07h 2 BYTEs ASCIZ thousands separator
09h 2 BYTEs ASCIZ decimal separator
0Bh 2 BYTEs ASCIZ date separator
0Dh 2 BYTEs ASCIZ time separator
0Fh BYTE currency format
bit 2 = set if currency symbol replaces decimal point
bit 1 = number of spaces between value and currency symbol
bit 0 = 0 if currency symbol precedes value
1 if currency symbol follows value
10h BYTE number of digits after decimal in currency
11h BYTE time format
bit 0 = 0 if 12-hour clock
1 if 24-hour clock
12h DWORD address of case map routine
(FAR CALL, AL = character to map to upper case [>= 80h])
16h 2 BYTEs ASCIZ data-list separator
18h 10 BYTEs reserved
Values for country code:
001h United States
002h Canadian-French
003h Latin America
01Fh Netherlands
020h Belgium
021h France
022h Spain
024h Hungary (not supported by DR-DOS 5.0)
026h Yugoslavia (not supported by DR-DOS 5.0)
027h Italy
029h Switzerland
02Ah Czechoslovakia (not supported by DR-DOS 5.0)
02Bh Austria (DR-DOS 5.0)
02Ch United Kingdom
02Dh Denmark
02Eh Sweden
02Fh Norway
030h Poland (not supported by DR-DOS 5.0)
031h Germany
037h Brazil (not supported by DR-DOS 5.0)
03Dh International English [Australia in DR-DOS 5.0]
051h Japan (DR-DOS 5.0)
052h Korea (DR-DOS 5.0)
15Fh Portugal
166h Finland
311h Middle East (DR-DOS 5.0)
3CCh Israel (DR-DOS 5.0)
----------2138-------------------------------
INT 21 - DOS 3+ - SET COUNTRY CODE
AH = 38h
AL = 01h thru 0FEh for specific country with code <255
AL = FFh for specific country with code >= 255
BX = 16-bit country code
DX = FFFFh
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
Note: not supported by OS/2
SeeAlso: INT 2F/AX=1403h
----------2139-------------------------------
INT 21 - DOS 2+ - "MKDIR" - CREATE SUBDIRECTORY
AH = 39h
DS:DX -> ASCIZ pathname
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h,05h) (see AH=59h)
Notes: all directories in the given path except the last must exist
fails if the parent directory is the root and is full
DOS 2.x-3.3 allow the creation of a directory sufficiently deep that
it is not possible to make that directory the current directory
because the path would exceed 64 characters
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=3Ah,AH=3Bh,AH=E2h/SF=0Ah,INT 2F/AX=1103h
----------213A-------------------------------
INT 21 - DOS 2+ - "RMDIR" - REMOVE SUBDIRECTORY
AH = 3Ah
DS:DX -> ASCIZ pathname of directory to be removed
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h,05h,06h,10h) (see AH=59h)
Notes: directory must be empty (contain only '.' and '..' entries)
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=39h,AH=3Bh,AH=E2h/SF=0Bh,INT 2F/AX=1101h
----------213B-------------------------------
INT 21 - DOS 2+ - "CHDIR" - SET CURRENT DIRECTORY
AH = 3Bh
DS:DX -> ASCIZ pathname to become current directory (max 64 bytes)
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h) (see AH=59h)
Notes: if new directory name includes a drive letter, the default drive is
not changed, only the current directory on that drive
changing the current directory also changes the directory in which
FCB file calls operate
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=47h,INT 2F/AX=1105h
----------213C-------------------------------
INT 21 - DOS 2+ - "CREAT" - CREATE OR TRUNCATE FILE
AH = 3CH
CX = file attribute
bit 0: read-only
1: hidden
2: system
3: volume label (ignored)
4: reserved, must be zero (directory)
5: archive bit
7: if set, file is shareable under Novell NetWare
DS:DX -> ASCIZ filename
Return: CF clear if successful
AX = file handle
CF set on error
AX = error code (03h,04h,05h) (see AH=59h)
Notes: if a file with the given name exists, it is truncated to zero length
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=16h,AH=3Dh,AH=5Ah,AH=5Bh,AH=93h
----------213D-------------------------------
INT 21 - DOS 2+ - "OPEN" - OPEN EXISTING FILE
AH = 3Dh
AL = access and sharing modes
bits 2-0: access mode
000 read only
001 write only
010 read/write
bit 3: reserved (0)
bits 6-4: sharing mode (DOS 3+)
000 compatibility mode
001 "DENYALL" prohibit both read and write access by others
010 "DENYWRITE" prohibit write access by others
011 "DENYREAD" prohibit read access by others
100 "DENYNONE" allow full access by others
bit 7: inheritance
if set, file is private to current process and will not be
inherited by child processes
DS:DX -> ASCIZ filename
CL = attribute mask of files to look for (server call only)
Return: CF clear if successful
AX = file handle
CF set on error
AX = error code (01h,02h,03h,04h,05h,0Ch) (see AH=59h)
Notes: file pointer is set to start of file
file handles which are inherited from a parent also inherit sharing
and access restrictions
files may be opened even if given the hidden or system attributes
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=0Fh,AH=3Ch,AX=4301h,AX=5D00h,INT 2F/AX=1226h
File sharing behavior:
| Second and subsequent Opens
First |Compat Deny Deny Deny Deny
Open | All Write Read None
|R W RW R W RW R W RW R W RW R W RW
- - - - -| - - - - - - - - - - - - - - - - -
Compat R |Y Y Y N N N 1 N N N N N 1 N N
W |Y Y Y N N N N N N N N N N N N
RW|Y Y Y N N N N N N N N N N N N
- - - - -|
Deny R |C C C N N N N N N N N N N N N
All W |C C C N N N N N N N N N N N N
RW|C C C N N N N N N N N N N N N
- - - - -|
Deny R |2 C C N N N Y N N N N N Y N N
Write W |C C C N N N N N N Y N N Y N N
RW|C C C N N N N N N N N N Y N N
- - - - -|
Deny R |C C C N N N N Y N N N N N Y N
Read W |C C C N N N N N N N Y N N Y N
RW|C C C N N N N N N N N N N Y N
- - - - -|
Deny R |2 C C N N N Y Y Y N N N Y Y Y
None W |C C C N N N N N N Y Y Y Y Y Y
RW|C C C N N N N N N N N N Y Y Y
Legend: Y = open succeeds, N = open fails with error code 05h
C = open fails, INT 24 generated
1 = open succeeds if file read-only, else fails with error code
2 = open succeeds if file read-only, else fails with INT 24
----------213DFF-----------------------------
INT 21 - VIRUS - "JD-448" - INSTALLATION CHECK
AX = 3DFFh
Return: AX = 4A44h if resident
SeeAlso: AX=357Fh,AX=4203h
----------213E-------------------------------
INT 21 - DOS 2+ - "CLOSE" - CLOSE FILE
AH = 3Eh
BX = file handle
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (06h) (see AH=59h)
Note: if the file was written to, any pending disk writes are performed, the
time and date stamps are set to the current time, and the directory
entry is updated
SeeAlso: AH=10h,AH=3Ch,AH=3Dh,INT 2F/AX=1106h,INT 2F/AX=1227h
----------213F-------------------------------
INT 21 - DOS 2+ - "READ" - READ FROM FILE OR DEVICE
AH = 3Fh
BX = file handle
CX = number of bytes to read
DS:DX -> buffer for data
Return: CF clear if successful
AX = number of bytes actually read (0 if at EOF before call)
CF set on error
AX = error code (05h,06h) (see AH=59h)
Notes: data is read beginning at current file position, and the file position
is updated after a successful read
the returned AX may be smaller than the request in CX if a partial
read occurred
if reading from CON, read stops at first CR
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=27h,AH=40h,AH=93h,INT 2F/AX=1108h,INT 2F/AX=1229h
----------213F-------------------------------
INT 21 - Turbo Debug HARDWARE BREAKPOINTS - READ STATUS BLOCK
AH = 3Fh
BX = handle for character device "TDHDEBUG"
CX = number of bytes to read
DS:DX -> buffer for status block (see below)
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (05h,06h) (see AH=59h)
SeeAlso: AH=40h"Turbo Debug"
Format of status block:
Offset Size Description
00h BYTE status of command
00h successful
01h invalid handle
02h no more breakpoints available
03h hardware does not support specified breakpoint type
04h previous command prevents execution
05h debugger hardware not found
06h hardware failure
07h invalid command
08h driver not initialized yet
FEh recursive entry (hardware breakpoint inside hw bp handler)
---status for command 01h---
01h WORD device driver interface version number (currently 1)
03h WORD device driver software version
05h BYTE maximum simultaneous hardware breakpoints
06h BYTE configuration bits
bit 0: CPU and DMA accesses are distinct
1: can detect DMA transfers
2: supports data mask
3: hardware pass counter on breakpoints
4: can match on data as well as addresses
07h BYTE supported breakpoint types
bit 0: memory read
1: memory write
2: memory read/write
3: I/O read
4: I/O write
5: I/O read/write
6: instruction fetch
08h WORD supported addressing match modes
bit 0: any address
1: equal to test value
2: not equal
3: above test value
4: below test value
5: below or equal
6: above or equal
7: within range
8: outside range
0Ah WORD supported data matches
bit 0: any data
1: equal to test value
2: not equal
3: above test value
4: below test value
5: below or equal
6: above or equal
7: within range
8: outside range
0Ch BYTE maximum data match length (01h, 02h, or 04h)
0Dh WORD size of onboard memory (in K)
0Fh WORD maximum number of trace-back events
11h WORD hardware breakpoint enable byte address segment (0000h if not
supported)
---status for command 04h---
01h BYTE handle to use when referring to the just-set breakpoint
----------213F-------------------------------
INT 21 - PC/TCP IPCUST.SYS - READ CONFIGURATION DATA
AH = 3Fh
BX = handle for character device "$IPCUST"
CX = number of bytes to read
DS:DX -> buffer for configuration data (see below)
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (05h,06h) (see AH=59h)
Notes: if less than the entire data is read or written, the next read/write
continues where the previous one ended; IOCTL calls AX=4402h and
AX=4403h both reset the location at which the next operation starts
to zero
the data pointer is also reset to zero if the previous read or write
reached or exceeded the end of the data, when the current function
is read and the previous was write, or vice versa
SeeAlso: AH=40h"IPCUST",AX=4402h"IPCUST"
Format of configuration data:
Offset Size Description
00h 12 BYTEs IPCUST.SYS device driver header
12h BYTE ???
13h BYTE ???
14h WORD ???
16h BYTE bit flags
bit 0: send BS rather than DEL for BackSpace key
bit 1: wrap long lines
17h BYTE ???
18h 64 BYTEs ASCIZ hostname
58h 64 BYTEs ASCIZ domain name
(fully qualified domain name is hostname.domain-name)
98h 16 BYTEs ASCIZ username
A8h 64 BYTEs ASCIZ full name
E8h 64 BYTEs ASCIZ office address
128h 32 BYTEs ASCIZ phone number
148h WORD offset from GMT in minutes
14Ah 4 BYTEs ASCIZ timezone name
14Eh WORD number of time servers
150h ? DWORDs IP addresses for time servers (big-endian)
???
164h WORD number of old-style name servers
166h 3 DWORDs IP addresses for name servers (big-endian)
172h WORD number of domain name servers
174h 3 DWORDs IP addresses for domain name servers (big-endian)
180h DWORD IP address of default gateway (big-endian)
184h DWORD IP address of log server (big-endian)
188h DWORD IP address of cookie server (big-endian)
18Ch DWORD IP address of lpr server (big-endian)
190h DWORD IP address of imagen print server
194h 54 BYTEs ???
1E8h WORD TCP default window size in bytes
1EAh WORD TCP low window size
1ECh 64 BYTEs ASCIZ host tabel filename
22Ch 2 BYTEs ???
22Eh 80 BYTEs ASCIZ mail relay host name
27Eh BYTE ???
27Fh BYTE ??? bit flags
280h 44 BYTEs ???
2ACh WORD ???
2AEh 202 BYTEs ???
----------2140-------------------------------
INT 21 - DOS 2+ - "WRITE" - WRITE TO FILE OR DEVICE
AH = 40h
BX = file handle
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 (05h,06h) (see AH=59h)
Notes: if CX is zero, no data is written, and the file is truncated or
extended to the current position
data is written beginning at the current file position, and the file
position is updated after a successful write
the usual cause for AX < CX on return is a full disk
BUG: a write of zero bytes will appear to succeed when it actually failed
if the write is extending the file and there is not enough disk
space for the expanded file (DOS 5.0); one should therefore check
whether the file was in fact extended by seeking to 0 bytes from
the end of the file (INT 21/AX=4202h/CX=0/DX=0)
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=28h,AH=3Fh,AH=93h,INT 2F/AX=1109h
----------2140-------------------------------
INT 21 - Turbo Debug HARDWARE BREAKPOINTS - SEND CMD TO HARDWARE BRKPNT DRIVER
AH = 40h
BX = handle for character device "TDHDEBUG"
CX = number of bytes to write
DS:DX -> hardware breakpoint command (see below)
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) (see AH=59h)
Note: results are retrieved by reading from the device
SeeAlso: AH=3Fh"Turbo Debug"
Format of hardware breakpoint commands:
Offset Size Description
00h BYTE command code
00h install interrupt vectors
01h get hardware capabilities
02h enable hardware breakpoints
03h disable hardware breakpoints
04h set hardware breakpoint
05h clear hardware breakpoint
06h set I/O base address and reset hardware
07h restore interrupt vectors
---command code 00h---
01h DWORD pointer to Turbo Debugger entry point to be jumped to on
hardware breakpoint; call with CPU state the same as on
the breakpoint except for pushing AX and placing an entry
code (FFh if breakout button or breakpoint handle) in AH
---command code 04h---
01h BYTE breakpoint type
00h memory read
01h memory write
02h memory read/write
03h I/O read
04h I/O write
05h I/O read/write
06h instruction fetch
02h BYTE address matching mode
00h any address
01h equal to test value
02h different from test value
03h above test value
04h below test value
05h below or equal to test value
06h above or equal to test value
07h within inclusive range
08h outside specified range
03h DWORD 32-bit linear low address
07h DWORD 32-bit linear high address
0Bh WORD pass count
0Dh BYTE data size (01h, 02h, or 04h)
0Eh BYTE source of matched bus cycle
01h CPU
02h DMA
03h either
0Fh BYTE data-matching mode
00h match any
01h equal to test value
02h different from test value
03h above test value
04h below test value
05h below or equal to test value
06h above or equal to test value
07h within specified range
08h outside specified range
10h DWORD low data value
14h DWORD high data value
18h DWORD data mask specifying which bits of the data are tested
---command code 05h---
01h BYTE handle of breakpoint to clear (breakpoint returned from command
04h)
---command code 06h---
01h WORD base address of hardware debugger board
----------2140-------------------------------
INT 21 - PC/TCP IPCUST.SYS - WRITE CONFIGURATION DATA
AH = 40h
BX = handle for character device "$IPCUST"
CX = number of bytes to write
DS:DX -> buffer for configuration data (AH=3Fh"IPCUST")
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) (see AH=59h)
Notes: if less than the entire data is read or written, the next read/write
continues where the previous one ended; IOCTL calls AX=4402h and
AX=4403h both reset the location at which the next operation starts
to zero
the data pointer is also reset to zero if the previous read or write
reached or exceeded the end of the data, when the current function
is read and the previous was write, or vice versa
SeeAlso: AH=3Fh"IPCUST",AX=4402h"IPCUST"
----------214000BX0002-----------------------
INT 21 - FARTBELL.EXE - INSTALLATION CHECK
AX = 4000h
BX = 0002h
CX = 0000h
DS:DX = 0000h:0000h
Return: CF clear if installed
AX = CS of resident code
Note: FARTBELL is a joke program by Guenther Thiele which makes various
noises when programs output a bell
SeeAlso: AX=4001h
----------214001BX0002-----------------------
INT 21 - FARTBELL.EXE - FORCE NOISE
AX = 4001h
BX = 0002h
CX = 0000h
DS:DX = 0000h:0000h
Note: FARTBELL is a joke program by Guenther Thiele which makes various
noises when programs output a bell
SeeAlso: AX=4000h
----------2141-------------------------------
INT 21 - DOS 2+ - "UNLINK" - DELETE FILE
AH = 41h
DS:DX -> ASCIZ filename (no wildcards, but see below)
CL = attribute mask for deletion (server call only, see below)
Return: CF clear if successful
AX destroyed (DOS 3.3) AL seems to be drive of deleted file
CF set on error
AX = error code (02h,03h,05h) (see AH=59h)
Notes: (DOS 3.1+) wildcards are allowed if invoked via AX=5D00h, in which case
the filespec must be canonical (as returned by AH=60h), and only
files matching the attribute mask in CL are deleted
DOS does not erase the file's data; it merely becomes inaccessible
because the FAT chain for the file is cleared
deleting a file which is currently open may lead to filesystem
corruption. Unless SHARE is loaded, DOS does not close the handles
referencing the deleted file, thus allowing writes to a nonexistant
file.
under DRDOS and DR Multiuser DOS, this function will fail if the file
is currently open
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=13h,AX=4301h,AX=5D00h,AH=60h,AX=F244h,INT 2F/AX=1113h
----------214101DXFFFE-----------------------
INT 21 - SoftLogic Data Guardian - ???
AX = 4101h
DX = FFFEh
Return: AX = 0000h if installed
Note: resident code sets several internal variables on this call
----------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)
SeeAlso: AH=24h,INT 2F/AX=1228h
----------214203-----------------------------
INT 21 - VIRUS - "Shake" - INSTALLATION CHECK
AX = 4203h
Return: AX = 1234h if resident
SeeAlso: AX=3DFFh,AX=4243h
----------214243-----------------------------
INT 21 - VIRUS - "Invader" - INSTALLATION CHECK
AX = 4243h
Return: AX = 5678h if resident
SeeAlso: AX=4203h,AX=4B04h
----------214300-----------------------------
INT 21 - DOS 2+ - GET FILE ATTRIBUTES
AX = 4300h
DS:DX -> ASCIZ filename
Return: CF clear if successful
CX = attributes (see AX=4301h)
AX = CX (DR-DOS 5.0)
CF set on error
AX = error code (01h,02h,03h,05h) (see AH=59h)
Note: under the FlashTek X-32 DOS extender, the filename pointer is in DS:EDX
SeeAlso: AX=4301h,AX=4310h,AH=B6h,INT 2F/AX=110Fh
----------214301-----------------------------
INT 21 - DOS 2+ - "CHMOD" - SET FILE ATTRIBUTES
AX = 4301h
CX = new attributes
bit 7: shareable (Novell NetWare)
6: unused
5: archive
4: directory
3: volume label
execute-only (Novell NetWare)
2: system
1: hidden
0: read-only
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)
MSDOS 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
SeeAlso: AX=4300h,AX=4311h,INT 2F/AX=110Eh
----------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
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
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+)
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
----------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
Note: if the file is already protected, the old password must be added after
the pathname, separated by a ";"
SeeAlso: AX=4302h,AX=4454h
----------214304-----------------------------
INT 21 - DR-DOS 5.0 internal - GET ???
AX = 4304h
???
Return: CF clear if successful
CX = AX = ???
CF set on error
AX = error code (see AH=59h)
SeeAlso: AX=4305h
----------214305-----------------------------
INT 21 - DR-DOS 5.0 internal - SET ???
AX = 4305h
???
Return: CF clear if successful
CF set on error
AX = error code (see AH=59h)
SeeAlso: AX=4304h
----------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
----------214310-----------------------------
INT 21 - Banyan VINES 2.1+ - SET EXTENDED FILE ATTRIBUTES
AX = 43100h
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=4310h,INT 2F/AX=110Eh
----------214400-----------------------------
INT 21 - DOS 2+ - IOCTL - GET DEVICE INFORMATION
AX = 4400h
BX = handle
Return: CF clear if successful
DX = device information word
character device
14: device driver can process IOCTL requests (see AX=4402h)
13: output until busy supported
11: driver supports OPEN/CLOSE calls
7: set (indicates device)
6: EOF on input
5: raw (binary) mode
4: device is special (uses INT 29)
3: clock device
2: NUL device
1: standard output
0: standard input
disk file
15: file is remote (DOS 3+)
14: don't set file date/time on closing (DOS 3+)
11: media not removable
8: (DOS 4+) generate INT 24 if no disk space on write
7: clear (indicates file)
6: file has not been written
5-0: drive number (0 = A:)
AX destroyed
CF set on error
AX = error code (01h,05h,06h) (see AH=59h)
Note: value in DH corresponds to high byte of device driver's attribute word
if handle refers to a character device
SeeAlso: AX=4401h,INT 2F/AX=122Bh
----------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
----------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
----------214402-----------------------------
INT 21 - Network Driver Interface Spec 2.0.1 - PROTOCOL MANAGER
AX = 4402h
BX = file handle for device "PROTMAN$"
DS:DX -> request block (see below)
CX = 000Eh (size of request block)
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
Values of 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
01h Media Access Control
02h Data link
03h network
04h transport
05h session
FFh not specified
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
00h physical
01h Media Access Control
02h Data link
03h network
04h transport
05h session
FFh not specified
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
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 DWORD reserved, must be 0
3Ch DWORD reserved, must be 0
Note: for compatibility with NDIS 1.x.x, a major version of 00h is
interpreted as 01h
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
bit 0: supports broadcast
1: supports multicast
2: supports functional/group addressing
3: supports promiscuous mode
4: station address software settable
5: statistics always current
6: supports InitiateDiagnostics
7: supports loopback
8: MAC does primarily ReceiveChain indications instead of
ReceiveLookahead indications
9: supports IBM source routing
10: supports MAC reset
11: supports Open/Close adapter
12: supports interrupt request
13: supports source routing bridge
14: supports GDT virtual addresses (OS/2 version)
15: multiple TransferDatas allowed durign a single
indication
16: MAC normally sets FrameSize = 0 in ReceiveLookahead
17-31: reserved, must be 0
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
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
bits 0-2: 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
4: MAC open
5: diagnostics in progress
6-31: reserved
0Ah WORD current packet filter flags
bit 0: directed/multicast or group/functional
1: broadcast
2: promiscuous
3: all source routing
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
----------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 ???
----------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
Note: LASTBYTE.SYS is part of "The Last Byte" by Key Software Products
SeeAlso: AX=4402h"HIGHUMM"
----------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
Note: HIGHUMM.SYS is part of "The Last Byte" 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
----------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
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
----------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
Format of control block:
Offset Size Description
00h BYTE 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
---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
bit 0: door open
1: door unlocked
2: supports raw reading in addition to cooked
3: writable
4: can play audio/video tracks
5: supports interleaving
6: reserved
7: supports prefetch requests
8: supports audio channel control
9: supports Red Book addressing in addition to HSG
10: audio is playing
---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"
----------214402-----------------------------
INT 21 U - 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)
SeeAlso: AX=4402h"HOOKROM",INT 2F/AX=D201h/BX=5145h,INT 67/AH=3Fh
----------214402-----------------------------
INT 21 U - Quarterdeck - QEMM-386 v6+ - GET ???
AX = 4402h
BX = file handle for device "EMMXXXX0"
CX = 0006h (size of buffer in bytes)
DS:DX -> buffer for ???
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)
Note: this call always returns an error if Windows3 support has been disabled
with the NW3 switch to QEMM386.SYS
SeeAlso: INT 2F/AX=D201h/BX=5145h,INT 67/AH=3Fh
----------214402-----------------------------
INT 21 U - Quarterdeck - HOOKROM.SYS - GET HOOKED VECTOR TABLE
AX = 4402h
BX = file handle for device "HOOKROM$"
CX = 0004h
DS:DX -> DWORD buffer for address of hooked vector table (see below)
Return: CF clear if successful
DS:DX buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h"QEMM"
Format of hooked vector table entry:
Offset Size Description
00h 5 BYTEs FAR jump to actual interrupt handler
(end of table if first byte is not EAh)
05h BYTE interrupt vector number
----------214402-----------------------------
INT 21 - Advanced SCSI Programming Interface (ASPI) - INTERFACE
AX = 4402h
BX = file handle for device "SCSIMGR$"
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
----------214402-----------------------------
INT 21 U - Qualitas 386MAX v6.00+ - IOCTL INPUT - GET STATE
AX = 4402h
BX = file handle for device "386MAX$$"
CX = 005Ah
DS:DX -> 386MAX state buffer (see below)
Return: CF clear if successful
buffer filled
AX = number of bytes actually copied
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Notes: the buffer must be one byte larger than the value given in CX; if the
value is less than 5Ah, only a partial state record will be returned
the state is 40h bytes for 386MAX (actually ASTEMM) v2.20 ("386MAX$$"
did not exist yet, use "QMMXXXX0" and then "EMMXXXX0" instead) and
56h bytes for v5.11.