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Interrupt List, part 4 of 12
This compilation is Copyright (c) 1989,1990,1991,1992,1993,1994,1995 Ralf Brown
--------X-1AB000-----------------------------
INT 1A U - HP 100LX/200LX - PCMCIA - ???
AX = B000h
ES:BX -> parameter block ???
Return: CF clear if ???
CF set if ???
Note: called by HP 100LX/200LX PCMCIA client CIC100.EXE
--------d-1AB001CX4D52-----------------------
INT 1A - Microsoft Real-Time Compression Interface (MRCI) - ROM-BASED SERVER
AX = B001h
CX = 4D52h ("MR")
DX = 4349h ("CI")
Return: CX = 4943h ("IC") if installed
DX = 524Dh ("RM") if installed
ES:DI -> MRCINFO structure (see #0523)
Note: this call is functionally identical to INT 2F/AX=4A12h, which should
be called first, as this call is used for the first, ROM-based
MRCI server, while the other call is used for RAM-based servers
which may be partially or entirely replacing a prior server
SeeAlso: INT 2F/AX=4A12h

Format of MRCINFO structure:
Offset Size Description (Table 0523)
00h 4 BYTEs vendor signature
"MSFT" Microsoft
04h WORD server version (high=major)
06h WORD MRCI specification version
08h DWORD address of server entry point (see #0525)
0Ch WORD bit flags: server capabilities (see #0524)
0Eh WORD bit flags: hardware assisted capabilities (see #0524)
10h WORD maximum block size supported by server (at least 8192 bytes)

Bitfields for MRCI capabilities:
Bit(s) Description (Table 0524)
0 standard compress
1 standard decompress
2 update compress
3 MaxCompress (not present in initial public release)
4 reserved
5 incremental decompress
6 MRCI 2.0 standard compress
7 MRCI 2.0 standard decompress
8-14 reserved
15 this structure is in ROM and can't be modified
(server capabilities only)

(Table 0525)
Call MRCI entry point with:
DS:SI -> MRCREQUEST structure (see #0526)
CX = type of client (0000h application, 0001h file system)
AX = operation
0001h perform standard compression
0002h perform standard decompression
0004h perform update compression
0008h perform MaxCompress
0020h perform incremental decompression
0040h perform MRCI 2.0 standard compression
0080h perform MRCI 2.0 standard decompression
AX = FFFFh clear flags
BX = bitmask of flags to clear (set bits in BX are flags to clear)
Return: AX = status
0000h successful
0001h invalid function
0002h server busy, try again
0003h destination buffer too small
0004h incompressible data
0005h bad compressed data format
BP destroyed (MS-DOS 6.2)
Note: MRCI driver may chain to a previous driver

Format of MRCREQUEST structure:
Offset Size Description (Table 0526)
00h DWORD pointer to source buffer
04h WORD size of source buffer (0000h = 64K)
06h WORD (UpdateCompress only)
(call) offset in source buffer of beginning of changed data
(return) offset in destination buffer of beginning of changed
compressed data
08h DWORD pointer to destination buffer
must contain original compressed data for UpdateCompress
0Ch WORD size of destination buffer (0000h = 64K)
any compression: size of buffer for compressed data
standard decompression: number of bytes to be decompressed
incremental decompression: number of byte to decompress now
(return) actual size of resulting data
0Eh WORD client compressed data storage allocation size
10h DWORD incremental decompression state data
set to 00000000h before first incremental decompression call
Notes: the source and destination buffers may not overlap
the source and destination buffer sizes should normally be the same
application should not update the contents of the MRCREQUEST structure
between incremental decompression calls
--------X-1AB101-----------------------------
INT 1A - Intel PCI BIOS v2.0c - INSTALLATION CHECK
AX = B101h
Return: AH = 00h if installed
CF clear
EDX = 20494350h (' ICP')
EDI = physical address of protected-mode entry point (see #0528)
AL = PCI hardware characteristics (see #0527)
BH = PCI interface level major version (BCD)
BL = PCI interface level minor version (BCD)
CL = number of last PCI bus in system
EAX, EBX, ECX, and EDX may be modified
all other flags (except IF) may be modified
Note: this function may require up to 1024 byte of stack; it will not enable
interrupts if they were disabled before making the call
SeeAlso: AX=B181h

Bitfields for PCI hardware characteristics:
Bit(s) Description (Table 0527)
0 configuration space access mechanism 1 supported
1 configuration space access mechanism 2 supported
2-3 reserved
4 Special Cycle generation mechanism 1 supported
5 Special Cycle generation mechanism 2 supported
6-7 reserved

(Table 0528)
Call protected-mode entry point with:
registers as for real/V86-mode INT call
CS = ring 0 descriptor with access to full address space
Return: as for real/V86-mode call
--------X-1AB102-----------------------------
INT 1A - Intel PCI BIOS v2.0c - FIND PCI DEVICE
AX = B102h
CX = device ID
DX = vendor ID
SI = device index (0-n)
Return: CF clear if successful
CF set on error
AH = status
00h successful
BH = bus number
BL = device/function number (bits 7-3 device, bits 2-0 func)
83h bad vendor ID
86h device not found
EAX, EBX, ECX, and EDX may be modified
all other flags (except IF) may be modified
Notes: this function may require up to 1024 byte of stack; it will not enable
interrupts if they were disabled before making the call
device ID FFFFh may be reserved as a wildcard in future implementations
the meanings of BL and BH on return were exchanged between the initial
drafts of the specification and final implementation
all devices sharing a single vendor ID and device ID may be enumerated
by incrementing SI from 0 until error 86h is returned
SeeAlso: AX=B182h
--------X-1AB103-----------------------------
INT 1A - Intel PCI BIOS v2.0c - FIND PCI CLASS CODE
AX = B103h
ECX = class code (bits 23-0)
SI = device index (0-n)
Return: CF clear if successful
CF set on error
AH = status
00h successful
BH = bus number
BL = device/function number (bits 7-3 device, bits 2-0 func)
86h device not found
EAX, EBX, ECX, and EDX may be modified
all other flags (except IF) may be modified
Notes: this function may require up to 1024 byte of stack; it will not enable
interrupts if they were disabled before making the call
the meanings of BL and BH on return were exchanged between the initial
drafts of the specification and final implementation
all devices sharing the same Class Code may be enumerated by
incrementing SI from 0 until error 86h is returned
SeeAlso: AX=B183h
--------X-1AB106-----------------------------
INT 1A - Intel PCI BIOS v2.0c - PCI BUS-SPECIFIC OPERATIONS
AX = B106h
BL = bus number
EDX = Special Cycle data
Return: CF clear if successful
CF set on error
AH = status
00h successful
81h unsupported function
EAX, EBX, ECX, and EDX may be modified
all other flags (except IF) may be modified
Note: this function may require up to 1024 byte of stack; it will not enable
interrupts if they were disabled before making the call
SeeAlso: AX=B186h
--------X-1AB108-----------------------------
INT 1A - Intel PCI BIOS v2.0c - READ CONFIGURATION BYTE
AX = B108h
BL = device/function number (bits 7-3 device, bits 2-0 function)
BH = bus number
DI = register number (0000h-00FFh)
Return: CF clear if successful
CL = byte read
CF set on error
AH = status
00h successful
87h bad register number
EAX, EBX, ECX, and EDX may be modified
all other flags (except IF) may be modified
Notes: this function may require up to 1024 byte of stack; it will not enable
interrupts if they were disabled before making the call
the meanings of BL and BH on return were exchanged between the initial
drafts of the specification and final implementation
SeeAlso: AX=B188h
--------X-1AB109-----------------------------
INT 1A - Intel PCI BIOS v2.0c - READ CONFIGURATION WORD
AX = B109h
BL = device/function number (bits 7-3 device, bits 2-0 function)
BH = bus number
DI = register number (0000h-00FFh)
Return: CF clear if successful
CX = word read
CF set on error
AH = status
00h successful
87h bad register number
EAX, EBX, ECX, and EDX may be modified
all other flags (except IF) may be modified
Notes: this function may require up to 1024 byte of stack; it will not enable
interrupts if they were disabled before making the call
the meanings of BL and BH on return were exchanged between the initial
drafts of the specification and final implementation
SeeAlso: AX=B189h
--------X-1AB10A-----------------------------
INT 1A - Intel PCI BIOS v2.0c - READ CONFIGURATION DWORD
AX = B10Ah
BH = bus number
BL = device/function number (bits 7-3 device, bits 2-0 function)
DI = register number (0000h-00FFh)
Return: CF clear if successful
ECX = dword read
CF set on error
AH = status
00h successful
87h bad register number
EAX, EBX, ECX, and EDX may be modified
all other flags (except IF) may be modified
Notes: this function may require up to 1024 byte of stack; it will not enable
interrupts if they were disabled before making the call
the meanings of BL and BH on return were exchanged between the initial
drafts of the specification and final implementation
SeeAlso: AX=B18Ah
--------X-1AB10B-----------------------------
INT 1A - Intel PCI BIOS v2.0c - WRITE CONFIGURATION BYTE
AX = B10Bh
BH = bus number
BL = device/function number (bits 7-3 device, bits 2-0 function)
DI = register number (0000h-00FFh)
CL = byte to write
Return: CF clear if successful
CF set on error
AH = status
00h successful
87h bad register number
EAX, EBX, ECX, and EDX may be modified
all other flags (except IF) may be modified
Notes: this function may require up to 1024 byte of stack; it will not enable
interrupts if they were disabled before making the call
the meanings of BL and BH on return were exchanged between the initial
drafts of the specification and final implementation
SeeAlso: AX=B18Bh
--------X-1AB10C-----------------------------
INT 1A - Intel PCI BIOS v2.0c - WRITE CONFIGURATION WORD
AX = B10Ch
BH = bus number
BL = device/function number (bits 7-3 device, bits 2-0 function)
DI = register number (multiple of 2 less than 0100h)
CX = word to write
Return: CF clear if successful
CF set on error
AH = status
00h successful
87h bad register number
EAX, EBX, ECX, and EDX may be modified
all other flags (except IF) may be modified
Notes: this function may require up to 1024 byte of stack; it will not enable
interrupts if they were disabled before making the call
the meanings of BL and BH on return were exchanged between the initial
drafts of the specification and final implementation
SeeAlso: AX=B18Ch
--------X-1AB10D-----------------------------
INT 1A - Intel PCI BIOS v2.0c - WRITE CONFIGURATION DWORD
AX = B10Dh
BH = bus number
BL = device/function number (bits 7-3 device, bits 2-0 function)
DI = register number (multiple of 4 less than 0100h)
ECX = dword to write
Return: CF clear if successful
CF set on error
AH = status
00h successful
87h bad register number
EAX, EBX, ECX, and EDX may be modified
all other flags (except IF) may be modified
Notes: this function may require up to 1024 byte of stack; it will not enable
interrupts if they were disabled before making the call
the meanings of BL and BH on return were exchanged between the initial
drafts of the specification and final implementation
SeeAlso: AX=B18Dh
--------X-1AB181-----------------------------
INT 1A - Intel PCI BIOS v2.0c - INSTALLATION CHECK (32-bit)
AX = B181h
Return: as for AX=B101h
SeeAlso: AX=B101h
--------X-1AB182-----------------------------
INT 1A - Intel PCI BIOS v2.0c - FIND PCI DEVICE (32-bit)
AX = B182h
CX = device ID
DX = vendor ID
SI = device index (0-n)
Return: as for AX=B102h
SeeAlso: AX=B102h
--------X-1AB183-----------------------------
INT 1A - Intel PCI BIOS v2.0c - FIND PCI CLASS CODE (32-bit)
AX = B183h
ECX = class code (bits 23-0)
SI = device index (0-n)
Return: as for AX=B103h
SeeAlso: AX=B103h
--------X-1AB186-----------------------------
INT 1A - Intel PCI BIOS v2.0c - PCI BUS-SPECIFIC OPERATIONS (32-bit)
AX = B186h
BL = bus number
EDX = Special Cycle data
Return: as for AX=B106h
SeeAlso: AX=B106h
--------X-1AB188-----------------------------
INT 1A - Intel PCI BIOS v2.0c - READ CONFIGURATION BYTE (32-bit)
AX = B188h
BL = bus number
BH = device/function number (bits 7-3 device, bits 2-0 function)
DI = register number (0000h-00FFh)
Return: as for AX=B108h
SeeAlso: AX=B108h
--------X-1AB189-----------------------------
INT 1A - Intel PCI BIOS v2.0c - READ CONFIGURATION WORD (32-bit)
AX = B189h
BL = bus number
BH = device/function number (bits 7-3 device, bits 2-0 function)
DI = register number (0000h-00FFh)
Return: as for AX=B109h
SeeAlso: AX=B109h
--------X-1AB18A-----------------------------
INT 1A - Intel PCI BIOS v2.0c - READ CONFIGURATION DWORD (32-bit)
AX = B18Ah
BL = bus number
BH = device/function number (bits 7-3 device, bits 2-0 function)
DI = register number (0000h-00FFh)
Return: as for AX=B10Ah
SeeAlso: AX=B10Ah
--------X-1AB18B-----------------------------
INT 1A - Intel PCI BIOS v2.0c - WRITE CONFIGURATION BYTE (32-bit)
AX = B18Bh
BL = bus number
BH = device/function number (bits 7-3 device, bits 2-0 function)
DI = register number (0000h-00FFh)
CL = byte to write
Return: as for AX=B10Bh
SeeAlso: AX=B10Bh
--------X-1AB18C-----------------------------
INT 1A - Intel PCI BIOS v2.0c - WRITE CONFIGURATION WORD (32-bit)
AX = B18Ch
BL = bus number
BH = device/function number (bits 7-3 device, bits 2-0 function)
DI = register number (multiple of 2 less than 0100h)
CX = word to write
Return: as for AX=B10Ch
SeeAlso: AX=B10Ch
--------X-1AB18D-----------------------------
INT 1A - Intel PCI BIOS v2.0c - WRITE CONFIGURATION DWORD (32-bit)
AX = B18Dh
BL = bus number
BH = device/function number (bits 7-3 device, bits 2-0 function)
DI = register number (multiple of 4 less than 0100h)
ECX = dword to write
Return: as for AX=B10Dh
SeeAlso: AX=B10Dh
--------X-1AB4-------------------------------
INT 1A - Intel Plug-and-Play BIOS Extensions - API
AH = B4h
AL = function (00h-07h)
further details not yet available
--------c-1AC0-------------------------------
INT 1A U - Disk Spool II v2.07+ - ALTERNATE INSTALLATION CHECK
AH = C0h
Return: (see AH=A0h)
Notes: this call is identical to AH=A0h
this function is also supported by Vertisoft's Emulaser utility ELSPL,
as that is a licensed version of Disk Spool II
SeeAlso: AH=A0h,AH=ABh,AH=D0h
--------U-1ACCCCBXCCCC-----------------------
INT 1A U - DATEFIX - INSTALLATION CHECK
AX = CCCCh
BX = CCCCh
CX = 0000h
Return: CX = CCCCh if installed
ES:BX -> original interrupt handler
Program: DATEFIX is a public-domain TSR to correct the date on AT&T 6300
machines, where the realtime clock's calendar wraps after 1991
SeeAlso: AH=FEh,AH=FFh"AT&T"
--------c-1AD0-------------------------------
INT 1A U - Disk Spool II v2.07+ - FUNCTION CALLS
AH = D0h
AL = function code
01h enable spooler and despooler
02h enable spooler only
03h enable despooler at beginning of file
04h disable the despooler
05h disable the despooler and spooler
06h clear the spool file
08h inhibit the popup menu
09h enable the popup menu
0Ah ??? (called by Disk Spool's INT 21 handler)
0Bh disable the spooler
0Ch start despooler after last successfully printed document
0Dh start despooler at the exact point where it last left off
0Eh pop up the menu
0Fh ???
11h start new spool file??? (called by Disk Spool's INT 21 handler
when a program terminates)
14h ???
15h delete despool file and reset ???
16h ??? (writes something to unknown file)
17h ??? (writes something to despool file, then reads something
else and ???)
18h ??? (reads something from despool file, and then ???)
19h ??? (creates/truncates spool file)
20h clear file pointed to by the despooler
21h ??? (writes something to unknown file)
22h ??? (writes something to spool file if spooler/despooler using
same file)
23h ??? (opens/creates unknown file, then ???)
30h ???
31h ???
32h beep
33h append CRLF to spool file???
34h ???
35h ???
36h ???
37h append CRLF to spool file and start a new spool file???
38h ???
40h ??? (v4.05)
41h ??? (v4.05)
51h ??? (called by Disk Spool's INT 21 handler)
52h ??? (called by Disk Spool's INT 21 handler)
57h ???
5Ah ??? (v4.05)
5Bh ??? (v4.05)
5Ch ??? (v4.05)
Note: this function is also supported by Vertisoft's Emulaser utility ELSPL,
as that is a licensed version of Disk Spool II
SeeAlso: AH=A0h,AH=ADh
--------c-1AE0-------------------------------
INT 1A - Disk Spool II v4.0x - ENABLE/DISABLE
AH = E0h
AL = subfunction
01h enable spooler
02h disable spooler
03h enable despooler
04h disable despooler
CL = printer port (01h COM1, 02h COM2, 05h LPT1, 06h LPT2)
Return: AH = status
00h successful
F0h printer port not managed by Disk Spool II
FFH failed
Note: this function is also supported by Vertisoft's Emulaser utility ELSPL,
as that is a licensed version of Disk Spool II
SeeAlso: AH=A0h,AH=E1h,AX=E301h,AX=E401h
--------c-1AE1-------------------------------
INT 1A - Disk Spool II v4.0x - GET STATUS
AH = E1h
CL = printer port (01h COM1, 02h COM2, 05h LPT1, 06h LPT2)
Return: AH = status
00h successful
CL = despooler state (00h disabled, 41h enabled)
CH = spooler state (00h disabled, 41h enabled)
DL = despooler activity (00h standing by, 41h printing)
ES:BX -> ASCIZ name of current spool file (or next if AutoSpool
or AutoDespool enabled)
ES:SI -> ASCIZ name of current despool file
ES:DI -> 3-byte file extension used by Disk Spool II
F0h printer port not managed by Disk Spool II
Note: this function is also supported by Vertisoft's Emulaser utility ELSPL,
as that is a licensed version of Disk Spool II
SeeAlso: AH=A0h,AH=E0h,AH=E2h
--------c-1AE2-------------------------------
INT 1A - Disk Spool II v4.0x - GET SPOOL FILES
AH = E2h
AL = which
01h first
02h next (can only call after "first")
CL = printer port (01h COM1, 02h COM2, 05h LPT1, 06h LPT2)
Return: AH = status
00h successful
ES:BX -> ASCIZ filename
F0h no (more) spool files
FFh failed
Note: this function is also supported by Vertisoft's Emulaser utility ELSPL,
as that is a licensed version of Disk Spool II
SeeAlso: AH=E0h,AH=E1h
--------c-1AE301-----------------------------
INT 1A - Disk Spool II v4.0x - GET SPOOL FILE STATUS
AX = E301h
ES:BX -> ASCIZ filename (max 32 chars)
Return: AH = status
00h successful
ES:SI -> spool file status record (see #0529)
F0h not a spool file
FFh failed
Note: this function is also supported by Vertisoft's Emulaser utility ELSPL,
as that is a licensed version of Disk Spool II
SeeAlso: AH=E0h,AX=E302h,AX=E401h

Format of Disk Spool II spool file status record:
Offset Size Description (Table 0529)
00h BYTE hour of creation or last update
01h BYTE minute of creation or last update
02h BYTE year-1980 of creation or last update
03h BYTE month of creation or last update
04h BYTE day of creation or last update
05h BYTE total number of copies to print
06h BYTE number of copies already printed
07h BYTE printer port (01h COM1, 02h COM2, 05h LPT1, 06h LPT2)
08h BYTE save status (00h delete after printing, 01h save)
09h BYTE file status
01h done printing, but being saved
02h on hold
03h queued for printing
04h being spooled
05h being despooled (i.e. printed)
0Ah 16 BYTEs ASCIZ description
1Ah 2 WORDs file size in bytes (high,low)
1Eh 2 WORDs bytes left to print (high,low)
--------c-1AE302-----------------------------
INT 1A - Disk Spool II v4.0x - UPDATE SPOOL FILE
AX = E302h
ES:BX -> ASCIZ filename (max 32 chars)
ES:SI -> spool file status record (see #0529)
Return: AH = status
00h successful
F0h not a spool file
FFh failed
Note: this function is also supported by Vertisoft's Emulaser utility ELSPL,
as that is a licensed version of Disk Spool II
SeeAlso: AH=E0h,AX=E301h,AX=E401h
--------c-1AE401-----------------------------
INT 1A - Disk Spool II v4.0x - SPOOL EXISTING FILE
AX = E401h
ES:BX -> ASCIZ filename (max 32 chars)
CL = printer port (01h COM1, 02h COM2, 05h LPT1, 06h LPT2)
Return: AH = status
00h successful
FFh failed
Note: this function is also supported by Vertisoft's Emulaser utility ELSPL,
as that is a licensed version of Disk Spool II
SeeAlso: AH=E1h,AX=E302h,AX=E402h
--------c-1AE402-----------------------------
INT 1A U - Disk Spool II v4.0x - SPOOL EXISTING FILE???
AX = E402h
ES:BX -> ASCIZ filename (max 32 chars)
CL = printer port (01h COM1, 02h COM2, 05h LPT1, 06h LPT2)
Return: AH = status
00h successful
FFh failed
Note: this function is also supported by Vertisoft's Emulaser utility ELSPL,
as that is a licensed version of Disk Spool II
SeeAlso: AH=E1h,AX=E302h,AX=E401h
--------c-1AE5-------------------------------
INT 1A U - Emulaser ELSPL.COM - ???
AH = E5h
???
Return: ???
Program: ELSPL.COM is a licensed version of Disk Spool II which is distributed
as part of Vertisoft's Emulaser PostScript emulator
SeeAlso: AH=A0h,INT 17/AH=03h
--------c-1AEE-------------------------------
INT 1A U - Disk Spool II v4.05 - ???
AH = EEh
AL = printer port???
???
Return: ???
Note: this function is also supported by Vertisoft's Emulaser utility ELSPL,
as that is a licensed version of Disk Spool II
SeeAlso: AH=E1h
--------U-1AF7-------------------------------
INT 1A - RighTime v1.1 - TEMPORARILY DISABLE
AH = F7h
Program: RighTime is a TSR by G.T. Becker which continuously adjusts the system
time to correct for clock drift
Note: any AH value from F0h-F7h or F9h-FEh will perform this function in
version 1.1, but F7h is the function called by transient portion
SeeAlso: AH=F8h,AH=FFh"RighTime"
--------U-1AF8-------------------------------
INT 1A - RighTime v1.1 - ENABLE
AH = F8h
Program: RighTime is a TSR by G.T. Becker which continuously adjusts the system
time to correct for clock drift
Note: RighTime is TeSseRact-compatible (see INT 2F/AX=5453h) and modifies its
TeSseRact program identifier based on its current state: "RighTime"
when enabled, "RighTim"F7h when disabled.
SeeAlso: AH=F7h,AH=FFh"RighTime"
--------b-1AFE-------------------------------
INT 1A - AT&T 6300 - READ TIME AND DATE
AH = FEh
Return: BX = day count (0 = Jan 1, 1984)
CH = hour
CL = minute
DH = second
DL = hundredths
SeeAlso: AX=CCCCh/BX=CCCCh,AH=FFh"AT&T",INT 21/AH=2Ah,INT 21/AH=2Ch
--------b-1AFF-------------------------------
INT 1A - AT&T 6300 - SET TIME AND DATE
AH = FFh
BX = day count (0 = Jan 1, 1984)
CH = hour
CL = minute
DH = second
DL = hundredths
Return: ???
SeeAlso: AX=CCCCh/BX=CCCCh,AH=FEh,INT 21/AH=2Bh,INT 21/AH=2Dh
--------U-1AFF-------------------------------
INT 1A - RighTime v1.1 - PERMANENTLY DISABLE
AH = FFh
Program: RighTime is a TSR by G.T. Becker which continuously adjusts the system
time to correct for clock drift
Note: upon being permanently disabled, RighTime closes the file handle
referencing its executable (which is updated with time correction
information every two minutes while RighTime is enabled).
--------s-1AFF00-----------------------------
INT 1A - SND - INSTALLATION CHECK???
AX = FF00h
Return: AL = version??? (02h)
AH = busy flag (00h if not in a SND call, 01h if SND currently active)
Note: the SND API is also supported by IC (Internal Commands) v2.0, a
shareware TSR by Geoff Friesen which extends COMMAND.COM's internal
command set
SeeAlso: AX=FF01h,AX=FF02h,AX=FF04h,AX=FF05h
--------s-1AFF01-----------------------------
INT 1A - SND - PAUSE
AX = FF01h
DX = number of clock ticks to delay
Return: AH = status
00h successful
01h SND busy
Notes: if successful, execution returns to the caller after the delay expires;
if SND is busy, execution returns immediately
the IC v2.0 implementation of this API makes no special allowance for
time rollover at midnight, which can cause the delay to be over one
hour if this function is called just before the BIOS time count
rolls over and the delay extends into the next day
SeeAlso: AX=FF00h,INT 15/AH=86h,INT 62/AX=0096h,INT 7F/AH=E8h,INT 80/BX=0009h
SeeAlso: INT E0/CL=BDh
--------s-1AFF02-----------------------------
INT 1A - SND - START SOUND
AX = FF02h
DX = frequency in Hertz (14h-FFFFh)
Return: AH = status
00h successful
01h SND busy
SeeAlso: AX=FF00h,AX=FF01h,AX=FF03h
--------s-1AFF03-----------------------------
INT 1A - SND - STOP SOUND
AX = FF03h
Return: AH = status
00h successful
01h busy
Note: turns off any sound currently being emitted by the PC's speaker unless
SND is currently busy processing an API call (this includes
background music). Use AX=FF05h to stop the sound even if an API
call is in progress.
SeeAlso: AX=FF00h,AX=FF02h,AX=FF05h
--------s-1AFF04-----------------------------
INT 1A - SND - PLAY MUSIC STRING IN BACKGROUND
AX = FF04h
DS:DX -> ASCIZ music string
Return: AH = status
00h successful (music begins playing in background)
01h busy
Note: the music string accepted by SND is not the same as that accepted by
BASIC and other programs which process music strings
SeeAlso: AX=FF00h,AX=FF05h,INT 80/BX=0006h
--------s-1AFF05-----------------------------
INT 1A - SND - UNCONDITIONALLY STOP SOUND
AX = FF05h
Return: AH = 00h (successful)
Note: this function is the same as AX=FF03h, but will stop the sound even if
SND is currently busy, such as playing background music
SeeAlso: AX=FF00h,AX=FF03h,INT 80/BX=0007h
--------B-1B---------------------------------
INT 1B C - KEYBOARD - CONTROL-BREAK HANDLER
Desc: this interrupt is automatically called when INT 09 determines that
Control-Break has been pressed
Note: normally points to a short routine in DOS which sets the Ctrl-C flag,
thus invoking INT 23h the next time DOS checks for Ctrl-C.
SeeAlso: INT 23
--------B-1C---------------------------------
INT 1C - TIME - SYSTEM TIMER TICK
Desc: this interrupt is automatically called on each clock tick by the INT 08
handler
Notes: this is the preferred interrupt to chain when a program needs to be
invoked regularly
not available on NEC 9800-series PCs
SeeAlso: INT 08,INT E2"PC Cluster"
--------B-1D---------------------------------
INT 1D - SYSTEM DATA - VIDEO PARAMETER TABLES
Note: the default parameter table (see #0530) is located at F000h:F0A4h for
100% compatible BIOSes
SeeAlso: INT 10/AH=00h

Format of video parameters:
Offset Size Description (Table 0530)
00h 16 BYTEs 6845 register values for modes 00h and 01h
10h 16 BYTEs 6845 register values for modes 02h and 03h
20h 16 BYTEs 6845 register values for modes 04h and 05h
30h 16 BYTEs 6845 register values for modes 06h and 07h
40h WORD bytes in video buffer for modes 00h and 01h
42h WORD bytes in video buffer for modes 02h and 03h
44h WORD bytes in video buffer for modes 04h and 05h
46h WORD bytes in video buffer for modes 06h and 07h
48h 8 BYTEs columns on screen for each of modes 00h through 07h
50h 8 BYTEs CRT controller mode bytes for each of modes 00h through 07h
--------B-1E---------------------------------
INT 1E - SYSTEM DATA - DISKETTE PARAMETERS
Note: the default parameter table (see #0531) is located at F000h:EFC7h for
100% compatible BIOSes
SeeAlso: INT 13/AH=0Fh,INT 41

Format of diskette parameter table:
Offset Size Description (Table 0531)
00h BYTE first specify byte
bits 7-4: step rate
bits 3-0: head unload time (0Fh = 240 ms)
01h BYTE second specify byte
bits 7-1: head load time (01h = 4 ms)
bit 0: non-DMA mode (always 0)
02h BYTE delay until motor turned off (in clock ticks)
03h BYTE bytes per sector (00h = 128, 01h = 256, 02h = 512, 03h = 1024)
04h BYTE sectors per track
05h BYTE length of gap between sectors (2Ah for 5.25", 1Bh for 3.5")
06h BYTE data length (ignored if bytes-per-sector field nonzero)
07h BYTE gap length when formatting (50h for 5.25", 6Ch for 3.5")
08h BYTE format filler byte (default F6h)
09h BYTE head settle time in milliseconds
0Ah BYTE motor start time in 1/8 seconds
--------B-1F---------------------------------
INT 1F - SYSTEM DATA - 8x8 GRAPHICS FONT
Desc: this vector points at 1024 bytes of graphics data, 8 bytes for each
character 80h-FFh
Note: graphics data for characters 00h-7Fh stored at F000h:FA6Eh in 100%
compatible BIOSes
SeeAlso: INT 10/AX=5000h,INT 43
--------b-1F12-------------------------------
INT 1F U - C&T "SuperState" BIOS - POWER OFF
AH = 12h
Return: none
Note: POWER OFF
--------b-1F17-------------------------------
INT 1F U - C&T "SuperState" BIOS - EXECUTE FAR PROC ROUTINE ON SuperState
AH = 17h
ES:DI -> far procedure
Return: all registers except AH,ES,DI
Note: You can change the BIOS area (F000h:0000h - F000h:FFFFh) only through
this function
--------b-1F19-------------------------------
INT 1F U - C&T "SuperState" BIOS - ENABLE AUTO WAKEUP AND SET TIME AND DATE
AH = 19h
AL = hour in BCD
BH = minutes in BCD
BL = seconds in BCD
CH = year century in BCD (must be 19h)
CL = year low in BCD
DH = month in BCD
DL = date in BCD
Return: CF clear
--------b-1F1C-------------------------------
INT 1F U - C&T "SuperState" BIOS - SET SUSPEND TIMEOUT
AH = 1Ch
BX = sec until suspend starts
Return: None
--------b-1F1D-------------------------------
INT 1F U - C&T "SuperState" BIOS - SET SLEEP TIMEOUT
AH = 1Dh
BX = sec until sleep starts
Return: None
--------J-1F90-------------------------------
INT 1F - NEC PC-9801 - COPY EXTENDED MEMORY
AH = 90h
ES:BX -> global descriptor table (see #0367 at INT 15/AH=87h)
CX = number of bytes to copy
SI = 0000h
DI = 0000h
Return: CF clear if successful
CF set on error
???
SeeAlso: INT 15/AH=87h
--------b-1FF5--BLFA-------------------------
INT 1F U - C&T "SuperState" BIOS - REQUEST PASSWORD INPUT
AH = F5h
BL = FAh
Return: none
Note: this function will not return until the correct password is entered
SeeAlso: AH=F5h/BL=FDh,AX=F5h/BL=FEh
--------b-1FF5--BLFD-------------------------
INT 1F U - C&T "SuperState" BIOS - ENCRYPT PASSWORD
AH = F5h
BL = FDh
CX:SI = input string
DX:DI = encrypted string
BH = length of input string
Return: CF set on error
SeeAlso: AH=F5h/BL=FAh,AX=F5h/BL=FEh
--------b-1FF5--BLFE-------------------------
INT 1F U - C&T "SuperState" BIOS - SET PASSWORD
AH = F5h
BL = FEh
CX:SI -> input string
BH = length of input string (if BH = 00h, clear password)
Return: CF set on error
Note: the input string must be encrypted by INT 1Fh/AH=F5h/BL=FDh
SeeAlso: AH=F5h/BL=FDh,AX=F5h/BL=FFh
--------b-1FF5--BLFF-------------------------
INT 1F U - C&T "SuperState" BIOS - GET ENCRYPTED PASSWORD
AH = F5h
BL = FFh
DX:DI = string buffer
Return: CF set on error
CF clear if successful
BH = length of input string (if BH = 00h, password is not valid)
DX:DI -> encrypted password string
SeeAlso: AH=F5h/BL=FDh,AX=F5h/BL=FEh
--------b-1FFB-------------------------------
INT 1F U - C&T "SuperState" BIOS - GET/SET CPU SPEED
AH = FBh
BL = function
00h get CPU speed
Return: AL = current CPU speed (00h = fast, 01h = slow)
01h set CPU speed
AL = new CPU speed (00h = fast, 01h = slow)
SeeAlso: AH=FCh/BL=00h
--------b-1FFC--BL00-------------------------
INT 1F U - C&T "SuperState" BIOS - GET ALARM STATUS
AH = FCh
BL = 00h
Return: AL = current alarm state (00h = disabled, 01h = enabled)
SeeAlso: AH=FCh/BL=01h,AH=FCh/BL=02h
--------b-1FFC--BL01-------------------------
INT 1F U - C&T "SuperState" BIOS - SET ALARM STATUS
AH = FCh
BL = 01h
AL = new alarm state (00h = disabled, 01h = enabled)
SeeAlso: AH=FCh/BL=00h,AH=FCh/BL=03h
--------b-1FFC--BL02-------------------------
INT 1F U - C&T "SuperState" BIOS - GET ALARM TIME
AH = FCh
BL = 02h
Return: CH = hour by BCD
CL = min by BCD
DH = sec by BCD
SeeAlso: AH=FCh/BL=00h,AH=FCh/BL=03h,AH=FCh/BL=04h
--------b-1FFC--BL03-------------------------
INT 1F U - C&T "SuperState" BIOS - SET ALARM TIME
AH = FCh
BL = 03h
CH = hour by BCD
CL = min by BCD
DH = sec by BCD
Return: CF set on error (incorrect time format or Alarm is not enable)
SeeAlso: AH=FCh/BL=01h,AH=FCh/BL=02h,AH=FCh/BL=05h
--------b-1FFC--BL04-------------------------
INT 1F U - C&T "SuperState" BIOS - GET ALARM DATE
AH = FCh
BL = 04h
Return: CH = year century by BCD
CL = year low by BCD
DH = month by BCD
DL = date by BCD
SeeAlso: AH=FCh/BL=02h,AH=FCh/BL=05h
--------b-1FFC--BL05-------------------------
INT 1F U - C&T "SuperState" BIOS - SET ALARM DATE
AH = FCh
BL = 05h
CH = year century by BCD
CL = year low by BCD
DH = month by BCD
DL = date by BCD
Return: CF set on error (incorrect date format or Alarm is not enable)
SeeAlso: AH=FCh/BL=03h,AH=FCh/BL=04h
--------b-1FFD--BL00-------------------------
INT 1F U - C&T "SuperState" BIOS - GET AUTO WAKE UP STATUS
AH = FDh
BL = 00h
Return: AL = current wake-up state (00h = disabled, 01h = enabled)
SeeAlso: AH=FDh/BL=01h,AH=FDh/BL=02h
--------b-1FFD--BL01-------------------------
INT 1F U - C&T "SuperState" BIOS - SET AUTO WAKE UP STATUS
AH = FDh
BL = 01h
AL = new wake-up state (00h = disabled, 01h = enabled)
SeeAlso: AH=FDh/BL=00h,AH=FDh/BL=03h
--------b-1FFD--BL02-------------------------
INT 1F U - C&T "SuperState" BIOS - GET AUTO WAKE UP TIME
AH = FDh
BL = 02h
Return: CH = hour by BCD
CL = min by BCD
DH = sec by BCD
SeeAlso: AH=FDh/BL=00h,AH=FDh/BL=03h
--------b-1FFD-------------------------------
INT 1F U - C&T "SuperState" BIOS - SET AUTO WAKE UP TIME
AH = FDh
BL = 3h
CH = hour by BCD
CL = min by BCD
DH = sec by BCD
Return: CF set on error (incorrect Time format or Auto Wake up is not enable)
SeeAlso: AH=FDh/BL=01h,AH=FDh/BL=02h
--------b-1FFD--BL04-------------------------
INT 1F U - C&T "SuperState" BIOS - GET AUTO WAKE UP DATE
AH = FDh
BL = 04h
Return: CH = year century in BCD
CL = year low in BCD
DH = month in BCD
DL = date in BCD
SeeAlso: AH=FDh/BL=02h,AH=FDh/BL=05h
--------b-1FFD--BL05-------------------------
INT 1F U - C&T "SuperState" BIOS - SET AUTO WAKE UP DATE
AH = FDh
BL = 05h
CH = year century in BCD
CL = year low in BCD
DH = month in BCD
DL = date in BCD
Return: CF set on error (incorrect date format or Auto Wake up is not enable)
SeeAlso: AH=FDh/BL=03h,AH=FDh/BL=04h
--------O-20---------------------------------
INT 20 - Minix - SEND/RECEIVE MESSAGE
AX = process ID of other process
BX -> message
CX = operation (1 send, 2 receive, 3 send&receive)
Program: Minix is a Version 7 Unix-compatible operating system by Andrew
Tanenbaum
Note: the message contains the system call number (numbered as in V7
Unix(tm)) and the call parameters
--------D-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
--------G-20---------------------------------
INT 20 - COMTROL HOSTESS i/ISA DEBUGGER - INVOKE FIRMWARE DEBUGGER
???
Return: ???
SeeAlso: INT 21"COMTROL"
--------G-21---------------------------------
INT 21 - COMTROL HOSTESS i/ISA DEBUGGER - GET SEGMENT FOR CONTROL PROGRAM USE
???
Return: AX = first segment available for control program use
SeeAlso: INT 20"COMTROL",INT 22"COMTROL"
--------D-2100-------------------------------
INT 21 - DOS 1+ - TERMINATE PROGRAM
AH = 00h
CS = PSP segment
Notes: Microsoft recommends using INT 21/AH=4Ch for DOS 2+
execution continues at the 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
--------D-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
--------D-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
--------D-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
--------D-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
--------D-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
--------D-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
--------D-2106--DLFF-------------------------
INT 21 - DOS 1+ - DIRECT CONSOLE INPUT
AH = 06h
DL = FFh
Return: ZF set if no character available
AL = 00h
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
this function reads from standard input, which is always the keyboard
under DOS 1.x, but may be redirected under DOS 2+
although the return of AL=00h when no characters are available is not
documented, some programs rely on this behavior
SeeAlso: AH=0Bh
--------D-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
--------D-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
--------D-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 are checked, and INT 23 is called if either 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"
--------D-210A-------------------------------
INT 21 - DOS 1+ - BUFFERED INPUT
AH = 0Ah
DS:DX -> buffer (see #0532)
Return: buffer filled with user input
Notes: ^C/^Break are checked, and INT 23 is called if either detected
reads from standard input, which may be redirected under DOS 2+
if the maximum buffer size (see #0532) is set to 00h, this call returns
immediately without reading any input
SeeAlso: AH=0Ch,INT 2F/AX=4810h

Format of DOS input buffer:
Offset Size Description (Table 0532)
00h BYTE maximum characters buffer can hold
01h BYTE (call) 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
--------K-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
Program: WCED is a free command-line editor and history utility by Stuart
Russell
SeeAlso: AH=FFh"CED"
--------D-210B-------------------------------
INT 21 - DOS 1+ - GET STDIN STATUS
AH = 0Bh
Return: AL = status
00h if no character available
FFh if character is available
Notes: ^C/^Break are checked, and INT 23 is called if either 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
--------v-210B56-----------------------------
INT 21 - VIRUS - "Perfume" - INSTALLATION CHECK
AX = 0B56h
Return: AX = 4952h if resident
SeeAlso: AX=0D20h,INT 12/AX=4350h/BX=4920h,INT 13/AH=F2h
--------D-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
--------D-210D-------------------------------
INT 21 - DOS 1+ - DISK RESET
AH = 0Dh
Return: (DOS 6 only) CF clear (earlier versions preserve CF)
Notes: This function writes all modified disk buffers to disk, but does not
update the 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
--------v-210D20-----------------------------
INT 21 - VIRUS - "Crazy Imp" - INSTALLATION CHECK
AX = 0D20h
Return: AX = 1971h if resident
SeeAlso: AX=0B56h,AH=30h/DX=ABCDh
--------D-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
--------v-210E--DLAD-------------------------
INT 21 U - Novell DOS 7 - SDRes v27.03 - INSTALLATION CHECK
AH = 0Eh
DL = ADh
Return: AL = BAh if installed
Program: SDRes is the resident portion of the Search&Destroy antiviral by
Fifth Generation Systems, as bundled with Novell DOS 7
Note: SDRes will terminate programs which test for the presence of viruses
using interrupt-based installation calls, saying that the program
may be infected
SeeAlso: AH=0Eh/DL=AEh,AH=0Eh/DL=AFh,AH=4Ah/BX=00B6h,INT 13/AX=A759h
--------v-210E--DLAE-------------------------
INT 21 U - Novell DOS 7 - SDRes v27.03 - CLEAR ??? FLAG
AH = 0Eh
DL = AEh
SeeAlso: AH=0Eh/DL=ADh,AH=0Eh/DL=AFh,INT 13/AX=A759h
--------v-210E--DLAF-------------------------
INT 21 U - Novell DOS 7 - SDRes v27.03 - SET ??? FLAG
AH = 0Eh
DL = AFh
SeeAlso: AH=0Eh/DL=ADh,AH=0Eh/DL=AEh,INT 13/AX=A759h
--------D-210F-------------------------------
INT 21 - DOS 1+ - OPEN FILE USING FCB
AH = 0Fh
DS:DX -> unopened File Control Block (see #0533)
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
DR-DOS checks password attached with AX=4303h
BUG: APPEND for DOS 3.3+ corrupts DX if the file is not found
SeeAlso: AH=10h,AH=16h,AH=3Dh,AX=4303h

Format of File Control Block:
Offset Size Description (Table 0533)
-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 #0830 at AX=5700h)
16h WORD time of last write (see #0829 at AX=5700h) (DOS 1.1+)
18h 8 BYTEs reserved (see #0534,#0535,#0536,#0537,#0538)
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 FCB reserved field for DOS 1.0:
Offset Size Description (Table 0534)
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 FCB reserved field for DOS 1.10-1.25:
Offset Size Description (Table 0535)
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 FCB reserved field for DOS 2.x:
Offset Size Description (Table 0536)
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 FCB reserved field for DOS 3.x:
Offset Size Description (Table 0537)
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 or device
bits 5-0: low six bits of device attribute word
---SHARE.EXE loaded, local file---
1Ah WORD starting cluster of file on disk
1Ch WORD (DOS 3.x) offset within SHARE of sharing record
(see #0802 at AH=52h)
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.

Format of FCB reserved field for DOS 5.0:
Offset Size Description (Table 0538)
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 or device
bits 5-0: low six bits of device attribute word
---SHARE.EXE loaded, local file---
1Ah WORD starting cluster of file on disk
1Ch WORD unique sequence number of sharing record
1Eh BYTE file attributes
1Fh BYTE unused???
---SHARE.EXE loaded, remote file---
1Ah WORD network handle
1Ch DWORD network ID
---SHARE not loaded, local device---
1Ah DWORD pointer to device driver header
1Eh 2 BYTEs unused???
---SHARE not loaded, local file---
1Ah BYTE extra info
bit 7: read-only attribute from SFT
bit 6: archive attribute from SFT
bits 5-0: high bits of sector number
1Bh WORD starting cluster of file
1Dh WORD low word of sector number containing directory entry
1Fh BYTE number of directory entry within sector
--------D-2110-------------------------------
INT 21 - DOS 1+ - CLOSE FILE USING FCB
AH = 10h
DS:DX -> File Control Block (see #0533)
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
--------D-2111-------------------------------
INT 21 - DOS 1+ - FIND FIRST MATCHING FILE USING FCB
AH = 11h
DS:DX -> unopened FCB (see #0533), 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
the data returned in the DTA is actually the drive number (or extended
FCB header and drive number) followed by the file's directory entry
(see #0539); this format happens to be compatible with an unopened
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:)
this function is used by many copy protection schemes to obtain the
starting cluster of a file
SeeAlso: AH=12h,AH=1Ah,AH=4Eh,INT 2F/AX=111Bh

Format of DOS directory entry:
Offset Size Description (Table 0539)
00h 8 BYTEs blank-padded filename
08h 3 BYTEs blank-padded file extension
0Bh BYTE attributes
0Ch 10 BYTEs reserved
used by DR-DOS to store file password
16h WORD time of creation or last update (see #0829 at AX=5700h)
18h WORD date of creation or last update (see #0830 at AX=5700h)
1Ah WORD starting cluster number
1Ch DWORD file size
--------D-2112-------------------------------
INT 21 - DOS 1+ - FIND NEXT MATCHING FILE USING FCB
AH = 12h
DS:DX -> unopened FCB (see #0533)
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
--------D-2113-------------------------------
INT 21 - DOS 1+ - DELETE FILE USING FCB
AH = 13h
DS:DX -> unopened FCB (see #0533), 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
MS-DOS allows deletion of read-only files with an extended FCB, whereas
Novell NetWare does not
SeeAlso: AH=41h,INT 2F/AX=1113h
--------D-2114-------------------------------
INT 21 - DOS 1+ - SEQUENTIAL READ FROM FCB FILE
AH = 14h
DS:DX -> opened FCB (see #0533)
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
--------D-2115-------------------------------
INT 21 - DOS 1+ - SEQUENTIAL WRITE TO FCB FILE
AH = 15h
DS:DX -> opened FCB (see #0533)
[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
--------D-2116-------------------------------
INT 21 - DOS 1+ - CREATE OR TRUNCATE FILE USING FCB
AH = 16h
DS:DX -> unopened FCB (see #0533), 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; this is how to create a volume label in the disk's root dir
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=10h,AH=3Ch
--------D-2117-------------------------------
INT 21 - DOS 1+ - RENAME FILE USING FCB
AH = 17h
DS:DX -> modified FCB (see also #0533)
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
Notes: subdirectories may be renamed using an extended FCB with the
appropriate attribute, as may volume labels
DR-DOS checks password attached with AX=4303h before permitting rename
SeeAlso: AH=0Fh,AH=13h,AX=4303h,AH=56h,INT 2F/AX=1111h
--------D-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 MS-DOS
SeeAlso: AH=1Dh,AH=1Eh,AH=20h,AX=4459h,INT 60/DI=0513h
--------D-2119-------------------------------
INT 21 - DOS 1+ - GET CURRENT DEFAULT DRIVE
AH = 19h
Return: AL = drive (00h = A:, 01h = B:, etc)
Note: Novell NetWare uses the fact that DOS 2.x COMMAND.COM issues this call
from a particular location every time it starts a command to
determine when to issue an automatic EOJ
SeeAlso: AH=0Eh,AH=47h,AH=BBh
--------D-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
--------D-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 #0540)
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

(Table 0540)
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)
FAh HP 200LX D: ROM disk, 16 sectors per track (995K)
HP 200LX E: (Stacker host drive ???)
F9h floppy, double-sided, 15 sectors per track (1.2M)
floppy, double-sided, 9 sectors per track (720K,3.5")
F8h hard disk
F0h other media
(e.g. floppy, double-sized, 18 sectors per track -- 1.44M,3.5")
--------D-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), or FFh if invalid drive
CX = bytes per sector
DX = total number of clusters
DS:BX -> media ID byte (see #0540)
Notes: 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
on a DBLSPACE drive, the total number of clusters is based on the
estimated compression ratio
SeeAlso: AH=1Bh,AH=36h
--------D-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 MS-DOS
SeeAlso: AH=18h,AH=1Eh,AH=20h,AX=4459h
--------D-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 MS-DOS 1.x
SeeAlso: AH=18h,AH=1Dh,AH=20h
--------D-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 #0541 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 MS-DOS 1.25 drive parameter block:
Offset Size Description (Table 0541)
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
--------D-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 MS-DOS
SeeAlso: AH=18h,AH=1Dh,AH=1Eh,AX=4459h
--------D-2121-------------------------------
INT 21 - DOS 1+ - READ RANDOM RECORD FROM FCB FILE
AH = 21h
DS:DX -> opened FCB (see #0533)
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
--------D-2122-------------------------------
INT 21 - DOS 1+ - WRITE RANDOM RECORD TO FCB FILE
AH = 22h
DS:DX -> opened FCB (see #0533)
[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
--------D-2123-------------------------------
INT 21 - DOS 1+ - GET FILE SIZE FOR FCB
AH = 23h
DS:DX -> unopened FCB (see #0533), 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)
Notes: not supported by MS Windows 3.0 DOSX.EXE DOS extender
MS-DOS returns nonsense if the FCB record number field is set to a very
large positive number, and status FFh if negative; DR-DOS returns the
correct file size in both cases
BUG: APPEND for DOS 3.3+ corrupts DX if the file is not found
SeeAlso: AH=42h
--------D-2124-------------------------------
INT 21 - DOS 1+ - SET RANDOM RECORD NUMBER FOR FCB
AH = 24h
DS:DX -> opened FCB (see #0533)
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
--------D-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
under DR-DOS 5.0+, this function does not use any of the DOS-internal
stacks and may thus be called at any time
Novell NetWare (except the new DOS Requester) monitors the offset of
any INT 24 set, and if equal to the value at startup, substitutes
its own handler to allow handling of network errors; this introduces
the potential bug that any program whose INT 24 handler offset
happens to be the same as COMMAND.COM's will not have its INT 24
handler installed
SeeAlso: AX=2501h,AH=35h
--------E-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"
--------E-212502-----------------------------
INT 21 P - 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
--------E-212503-----------------------------
INT 21 P - 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
--------E-212504-----------------------------
INT 21 P - 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
--------E-212505-----------------------------
INT 21 P - 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
--------E-212506-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - SET INT TO ALWAYS GAIN CNTRL IN PR. 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
--------E-212507-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - SET REAL- & PROTECTED-MODE INT VECTORS
AX = 2507h
CL = interrupt number
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
--------E-212508-----------------------------
INT 21 P - 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
--------E-212509-----------------------------
INT 21 P - 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
--------E-212509-----------------------------
INT 21 P - 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
--------E-21250A-----------------------------
INT 21 P - 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
--------E-21250C-----------------------------
INT 21 P - 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
--------E-21250D-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - GET REAL-MODE LINK INFORMATION
AX = 250Dh
Return: CF clear
EAX = CS:IP of real-mode callback procedure (see #0542) 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

(Table 0542)
Call Phar Lap real-mode callback with:
STACK: DWORD offset to protected-mode code
WORD placeholder for protected-mode CS
DWORD pointer to selector structure (see #0543)
or 0000h:0000h for defaults
var parameters for protected-mode procedure
Return: via FAR return

Format of Phar Lap selector structure:
Offset Size Description (Table 0543)
00h WORD protected-mode GS selector
02h WORD protected-mode FS selector
04h WORD protected-mode ES selector
06h WORD protected-mode DS selector
--------E-21250E-----------------------------
INT 21 P - 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
--------E-21250F-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - CONVERT PROTECTED-MODE ADDRESS TO MS-DOS
AX = 250Fh
ES:EBX = 48-bit protected-mode address to convert
ECX = 00000000h or length of data in bytes
Return: CF clear if successful (address < 1MB and contiguous)
ECX = 32-bit real-mode MS-DOS address
CF set on error (address >= 1MB or not contiguous)
ECX = linear address
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2510h
--------E-212510-----------------------------
INT 21 P - 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 #0544)
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 Phar Lap real-mode call parameter block:
Offset Size Description (Table 0544)
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
--------E-212511-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - ISSUE REAL-MODE INTERRUPT
AX = 2511h
DS:EDX -> parameter block (see #0545)
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 Phar Lap real-mode interrupt parameter block:
Offset Size Description (Table 0545)
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
--------E-212512-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - LOAD PROGRAM FOR DEBUGGING
AX = 2512h
DS:EDX -> pointer to ASCIZ program name
ES:EBX -> pointer to parameter block (see #0547)
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 (see #0546)
SeeAlso: AX=2517h

(Table 0546)
Values for Phar Lap 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 Phar Lap program load parameter block:
Offset Size Description (Table 0547)
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
--------E-212513-----------------------------
INT 21 P - 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
--------E-212514-----------------------------
INT 21 P - 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
--------E-212515-----------------------------
INT 21 P - 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
--------E-212516-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender v2.2+ - FREE ALL MEMORY OWNED BY LDT
AX = 2516h
Return: CF clear
Note: this function must be called from Ring 0 or the CS descriptor is freed
--------E-212517-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender v2.1c+ - GET INFO ON DOS DATA BUFFER
AX = 2517h
Return: CF clear
ES:EBX -> data buffer (protected mode address)
ECX -> data buffer (real mode address)
EDX = size of data buffer in bytes
Note: the data buffer's address changes after calls to AX=2512h and AX=252Ah
SeeAlso: AX=2512h,AX=252Ah,AX=2530h
--------E-212518-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender 2.1c+ - SPECIFY HANDLER FOR MOVED SEGMENTS
AX = 2518h
ES:EBX -> function to call when a segment is moved
Return: CF clear
ES:EBX -> previous handler
--------E-212519-----------------------------
INT 21 P - 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
--------E-21251A-----------------------------
INT 21 P - 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
--------E-21251B-----------------------------
INT 21 P - 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
--------E-21251C-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM v2.1c+ - FREE PHYSICAL MEMORY PAGES
AX = 251Ch
BH = preservation flag (00h preserve contents, 01h discard contents)
EDX = number of pages to free
BL = address type
00h linear address
ECX = linear address of first page to be freed
01h pointer
ES:ECX -> first page to be freed
Return: CF clear if successful
CF set on error
EAX = error code
08h memory error, swap space full, no VMM or DPMI
09h invalid address
--------E-21251D-----------------------------
INT 21 OP - Phar Lap 386/DOS-Extender VMM v2.1c - READ PAGE-TABLE ENTRY
AX = 251Dh
BL = address type
00h linear address
ECX = linear address of page table entry to read
01h pointer
ES:ECX -> page table entry to read
Return: CF clear if successful
EAX = contents of page table entry
CF set on error
EAX = error code
09h invalid address or NOPAGE option set
78h invalid under DPMI
Note: this function is obsolete; use AX=252Bh/BH=09h instead
SeeAlso: AX=251Eh,AX=252Bh/BH=09h,AX=EB00h,INT 31/AX=0506h
--------E-21251E-----------------------------
INT 21 OP - Phar Lap 386/DOS-Extender VMM v2.1c - WRITE PAGE-TABLE ENTRY
AX = 251Eh
BL = address type
00h linear address
ECX = linear address of page table entry to read
01h pointer
ES:ECX -> page table entry to read
EDX = new value for page table entry
Return: CF clear if successful
CF set on error
EAX = error code
09h invalid address or NOPAGE option set
82h not compatible with DPMI
Note: this call is obsolete; use AX=252Bh/BH=0Ah instead
SeeAlso: AX=251Dh,AX=252Bh/BH=0Ah,INT 31/AX=0507h
--------E-21251F-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - EXHANGE TWO PAGE-TABLE ENTRIES
AX = 251Fh
BL = address type
00h linear address
ECX = linear address of first page table entry
EDX = linear address of second page table entry
01h pointer
ES:ECX -> first page table entry
ES:EDX -> second page table entry
Return: CF clear if successful
CF set on error
EAX = error code
09h invalid address or NOPAGE option set
82h not compatible with DPMI
SeeAlso: AX=251Dh,AX=251Eh
--------E-212520-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - GET MEMORY STATISTICS
AX = 2520h
DS:EDX -> pointer to buffer at least 100 bytes in size (see #0548)
BL = 0 (don't reset VM stats), 1 (reset VM stats)
Return: carry flag clear

Format of Phar Lap VM statistics buffer:
Offset Size Description (Table 0548)
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 pages to which swap file can be increased
50h DWORD "vmflags"
bit 0 = 1 if page fault in progress
---v4.0+ ---
54h DWORD number of physical pages guaranteed to be free
58h DWORD number of free physical pages currently available
5Ch DWORD size in pages of largest free block of memory (including disk
swap space)
60h DWORD reserved
--------E-212521-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - LIMIT PROGRAM'S EXTENDED MEM 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
--------E-212522-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v2.2+ - SPECIFY ALTERNATE PAGE-FAULT HANDLR
AX = 2522h
ES:EBX -> alternate handler for page faults
Return: CF clear
ES:EBX -> previous page-fault handler
SeeAlso: AX=2523h
--------E-212523-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v2.2+ - SPECIFY OUT-OF-SWAP-SPACE HANDLER
AX = 2523h
???
Return: ???
Note: this function takes a DWORD pointer and a DWORD pointer to a DWORD
pointer as arguments
SeeAlso: AX=2522h
--------E-212524-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v2.2+ - INSTALL PAGE-REPLACEMENT HANDLERS
AX = 2524h
???
Return: ???
Note: this function takes three DWORD pointers and three DWORD pointers to
DWORD pointers as arguments
--------E-212525-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - LIMIT PROGRAM'S CONVENT'L 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
--------E-212526-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - GET CONFIGURATION INFORMATION
AX = 2526h
???
Return: ???
Notes: details are not yet available
this function takes a pointer to the configuration buffer (see #0549)
and a poitner to a BYTE as arguments

Format of Phar Lap configuration buffer:
Offset Size Description (Table 0549)
00h DWORD flags 1 (see #0550)
04h DWORD flags 2 (unused through v5.0)
08h DWORD flags 3 (unused through v5.0)
0Ch DWORD 386|DOS-Extender major version
10h DWORD 386|DOS-Extender minor version
14h DWORD first letter of text after minor version number in version str
18h DWORD beta flag (00h normal release, 01h beta release)
1Ch DWORD processor (3 = 386, 4 = 486)
20h DWORD coprocessor (4 = none, 6 = 287, 7 = 387/486)
24h DWORD Weitek coprocessor flag (0 = none, 1 = present)
28h DWORD machine type (0 = IBM PC compatible, 1 = NEC 9800 series)
2Ch DWORD machine class
IBM: bus type (0=ISA, 1=MCA, 2=XT, 3=EISA)
NEC: 0=normal mode, 1=high-res mode
30h DWORD VCPI flag (0 = none, 1 = present)
34h DWORD -WEITEK/-1167 switch (0 = AUTO, 1 = ON, 2 = OFF)
38h DWORD -MINREAL setting
3Ch DWORD -MAXREAL setting
40h DWORD -MINIBUF setting
44h DWORD -MAXIBUF setting
48h DWORD size in bytes of DOS call data buffer
4Ch DWORD number of interrupt stacks (-NISTACK)
50h DWORD interrupt stack size (-ISTKSIZE)
54h DWORD -REALBREAK setting
58h DWORD -CALLBUFS
5Ch DWORD -HWIVEC
60h DWORD -PRIVEC
64h DWORD -INTMAP
68h DWORD -PRIMAP
6Ch DWORD VCPI: master 8259 interrupt vector base (IRQ0 mapping)
70h DWORD VCPI: slave 8259 interrupt vector base (IRQ8 mapping)
74h DWORD BIOS print screen interrupt vector (0 if NEC)
78h DWORD -EXTLOW setting
7Ch DWORD -EXTHIGH setting
80h DWORD lowest physical extended-memory address allocatable
84h DWORD highest physical extended-memory address allocatable + 1
88h DWORD special memory's physical base address (00000000h if none)
8Ch DWORD special memory size in bytes (00000000h if none)
90h DWORD -MAXVCPIMEM setting
94h DWORD -VSCAN
98h DWORD -SWAPCHK (0 = OFF, 1 = ON, 2 = FORCE, 3 = MAX)
9Ch DWORD -CODESIZE setting
A0h DWORD minimum swap file size (-MINSWFSIZE)
A4h DWORD maximum swap fiel size (-MAXSWFSIZE)
A8h DWORD page replacement policy (0 = LFU, 1 = NUR)
ACh DWORD number of GDT entries (-NGDTENT)
B0h DWORD number of LDT entries (-NLDTENT)
B4h DWORD program's privilege level (0-3)
---386|DOS-Extender v3.0+ ---
B8h DWORD -LOCKSTACK setting
BCh DWORD -MAXEXTMEM
C0h DWORD -MAXXMSMEM
C4h DWORD -MAXPGMMEM
C8h DWORD -DATATHRESHOLD
CCh DWORD virtual memory manager flag (0 = not present, 1 = present)
D0h DWORD Cyrix coprocessor flag (0 = no Cyrix EMC387, 1 = present)
D4h DWORD -CYRIX setting (0 = AUTO, 1 = ON, 2 = OFF)
D8h DWORD DPMI flag (0 = not present, 1 = present)
DCh DWORD DPMI major version
E0h DWORD DPMI minor version
E4h DWORD DPMI capabilities flags (see #0551)
E8h DWORD VCPI major version
ECh DWORD VCPI minor version
F0h WORD VCPI: IRQ0-7 physical base interrupt vector
F2h WORD VCPI: IRQ8-15 physical base interrupt vector
F4h DWORD XMS flag (0 = none, 1 = present)
F8h DWORD XMS major version
FCh DWORD XMS minor version
100h WORD application's CS selector
102h WORD application's DS selector
104h WORD application's PSP selector
106h WORD application's environment selector
108h WORD selector mapping entire first megabyte
10Ah WORD selector mapping text video memory
10Ch WORD selector mapping video memory (text for IBM, graphics for NEC)
10Eh WORD selector mapping Weitek address space, 0000h if not present
110h WORD selector mapping Cyrix EMC387 address space, 0000h if none
112h WORD reserved (0)
114h DWORD real-mode FAR entry point to call to switch to protected mode
with no saved context
118h DWORD size of LDT in bytes
---386|DOS-Extender v5.0+ ---
11Ch DWORD Windows flag (0 = not present, 1 = Windows present)
120h DWORD Windows major version
124h DWORD Windows minor version
128h DWORD Windows mode (0 = real/standard, 1 = enhanced)
12Ch DWORD OS/2 flag (0 = not present, 1 = OS/2 present)
130h DWORD OS/2 major version
134h DWORD OS/2 minor version
138h 50 DWORDs reserved (0)

Bitfields for flags 1:
Bit(s) Description (Table 0550)
0 -NOPAGE specified
1 -A20 specified
2 -VDISK specified
3 -XT specified
4 -AT specified
5 -MCA specified
6 -EISA specified
7 -NORMRES specified (NEC only)
8 -HIGHRES specified (NEC only)
9 set if -SWFGROW1ST, clear if -NOSWFGROW1ST
10 -NOVM specified
11 -SAVEREGS specified
12 unused (clear)
13 -NOVCPI specified
14 -NOMUL specified
15 -NOBMCHK specified
16 -NOSPCLMEM or -NOBIM
17 -NOPGEXP specified
18 -SWAPDEFDISK specified
---v3.0+ ---
19 -SAVEINTS specified
20 -NOLOAD specified
21 -PAGELOG specified
22 -OPENDENY specified
23 -ERRATA17 specified
---v4.1+ ---
24 -NESTDPMI specified
25 -NONESTDPMI specified
26 -NODPMI specified
27 -NOPCDWEITEK specified
---v4.2+ ---
28 -WININT21 specified

Bitfields for DPMI capabilities flags:
Bit(s) Description (Table 0551)
0 paging supported
1 physical device mapping
2 conventional memory mapping
3 exceptions restartable
--------E-212527-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - EN/DISABLE STATE SAVE ON INTERRUPTS
AX = 2527h
EBX = new status (00h disabled, 01h enabled)
Return: CF clear
EBX = previous state save flag
SeeAlso: AX=2528h
--------E-212528-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - READ REGISTERS AFTER CTRL-C INT
AX = 2528h
DS:EBX -> buffer for registers (see #0552)
Return: CF clear if successful
DS:EBX buffer filled
CF set on error
EAX = error code
83h interrupt state save not enabled
84h no active interrupt
SeeAlso: AX=2527h

Format of Phar Lap buffer for registers:
Offset Size Description (Table 0552)
00h 8 BYTEs unused
08h 4 DWORDs EAX,EBX,ECX,EDX
18h 4 DWORDs ESI,EDI,EBP,ESP
28h 6 WORDs CS,DS,SS,ES,FS,GS
34h DWORD EIP
38h DWORD EFLAGS
--------E-212529-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - LOAD FLAT MODEL .EXP or .REX FILE
AX = 2529h
???
Return: ES:EBX -> parameter block (see #0553)
???
Note: details not available at this time
SeeAlso: AX=252Ah

Format of Phar Lap program load parameter block:
Offset Size Description (Table 0553)
00h DWORD initial EIP
04h WORD initial CS
06h DWORD initial ESP
0Ah WORD initial SS
0Ch 4 WORDs initial DS, ES, FS, GS
14h DWORD minimum size in bytes of program segment
18h DWORD bytes of additional memory allocated
1Ch DWORD flags
bit 0: child linked with -UNPRIVILEGED
---v6.0+ ---
bit 1: child is PE file instead of .EXP
bit 2: loaded file is a DLL
bits 3-31 reserved
---v6.0+ ---
20h DWORD module handles (PE files only)
24h 7 DWORDs reserved (0)
--------E-21252A-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM - NEW LOAD PROGRAM FOR DEBUG
AX = 252Ah
DS:EDX -> ASCIZ program name
ES:EBX -> parameter block (see #0547)
ECX = size of LDT buffer in bytes
ESI = bit flags
bit 0: allow demand paging rather than loading entire program
bit 1: demand page from swap file rather than from .EXP
Return: CF clear if successful
EAX = VMM handle or FFFFFFFFh if none
ECX = number of descriptors in LDT buffer
CF set on error
EAX = error code
02h file error
EBX = file error code (see #0554)
ECX = DOS error code if EBX=1,2,3, or 8
08h insufficient memory
EBX = memory error code (see #0555)
80h LDT buffer too small
87h called twice without intervening call to AX=2531h
SeeAlso: AX=2512h,AX=2517h,AX=2529h,AX=2531h

(Table 0554)
Values for Phar Lap file error code:
01h DOS open error
02h DOS seek error
03h DOS read error
04h not an .EXP or .REX file
05h invalid file format
06h -OFFSET is not a multiple of 64K
07h -NOPAGE incompatible with -REALBREAK/-OFFSET
08h DOS error loading .EXE file

(Table 0555)
Values for Phar Lap memory error code:
01h out of physical memory
02h out of swap space
04h unable to change extended memory allocation
05h -MAXPGMMEM exceeded
06h insufficient low memory to REALBREAK value
07h insufficient low memory for PSP and environment
--------E-21252BBH00-------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - CREATE UNMAPPED PAGES
AX = 252Bh
BH = 00h
???
Return: ???
--------E-21252BBH01-------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - CREATE ALLOCATED PAGES
AX = 252Bh
BH = 01h
???
Return: ???
--------E-21252BBH02-------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - CREATE PHYSICAL DEVICE PAGES
AX = 252Bh
BH = 02h
???
Return: ???
--------E-21252BBH03-------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - MAP DATA FILE
AX = 252Bh
BH = 03h
???
Return: ???
SeeAlso: AX=252Bh/BL=0Bh
--------E-21252BBH04-------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - GET PAGE TYPES
AX = 252Bh
BH = 04h
???
Return: ???
Note: returns one word per page
SeeAlso: #0556

Bitfields for Phar Lap page information:
Bit(s) Description (Table 0556)
7 mapped to read/write data file
6 mapped to read-only data file
5 swapped to disk
4 locked
3-0 page type
0 unmapped
1 allocated
2 physical device page
--------E-21252B-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - 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: this function is also supported by FlashTek X-32VM; if X-32 is not
using virtual memory, this function always succeeds
--------E-21252B-----------------------------
INT 21 Pu - Phar Lap 386/DOS-Extender - FREE PHYSICAL PAGES
AX = 252Bh
BH = function (07h,08h)
???
Return: ???
--------E-21252BBH09-------------------------
INT 21 P - Phar Lap 386/DOS-Extender v4.1 - GET PAGETABLE ENTRY/PAGE TABLE INFO
AX = 252Bh
BH = 09h
BL = subfunction
00h get page table entry by linear address
ECX = linear address for which to get page table entry
01h get page table entry by logical address
ES:ECX = address for which to get page table entry
Return: CF clear if successful
EAX = page table entry
EBX = additional page table information
CF set on error
EAX = error code
0009h invalid address
0082h running under DPMI
SeeAlso: AX=251Dh,AX=252Bh/BH=0Ah
--------E-21252BBH0A-------------------------
INT 21 P - Phar Lap 386/DOS-Extender v4.1 - SET PAGETABLE ENTRY/PAGE TABLE INFO
AX = 252Bh
BH = 0Ah
BL = subfunction
00h set page table entry for linear address
ECX = linear address for which to get page table entry
01h set page table entry for logical address
ES:ECX = address for which to get page table entry
ESI = page table entry
EDI = additional page table information
Return: CF clear if successful
CF set on error
EAX = error code
0009h invalid address
0082h running under DPMI
SeeAlso: AX=252Bh/BH=09h
--------E-21252BBH0B-------------------------
INT 21 P - Phar Lap 386/DOS-Extender v4.1+ - MAP DATA FILE AT FILE OFFSET
AX = 252Bh
BH = 0Bh
BL = subfunction
00h by linear address
ECX = linear address at which to map data file
01h by logical address
ES:ECX = logical address at which to map data file
EDX = number of bytes to map
DS:ESI -> mapping structure (see #0557)
DS:EDI -> ASCIZ filename
Return: CF clear if successful
CF set on error
EAX = error code
0002h file error
ECX = phase (01h opening file, 02h seeking, 03h reading)
EDX = error code returned by DOS
0009h invalid address
0081h invalid parameters or 386|VMM not present
0086h all 386|VMM file handles already in use
SeeAlso: AX=252Bh/BH=03h,AX=252Bh/BH=09h

Format of Phar Lap mapping structure:
Offset Size Description (Table 0557)
00h DWORD starting file offset to be mapped
04h DWORD DOS file access and sharing modes (see #0586 at INT 21/AH=3Dh)
--------E-21252C-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v3.0 - ADD UNMAPPED PAGES AT END OF SEGMENT
AX = 252Ch
BX = segment selector
ECX = number of 4K pages to add
Return: CF clear if successful
EAX = offset in segment of beginning of unmapped pages
CF set on error
EAX = error code
08h insufficent memory
09h invalid selector
82h not supported by current DPMI
--------E-21252D-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM v2.3+ - CLOSE VMM FILE HANDLE
AX = 252Dh
EBX = VMM file handle
Return: CF clear if successful
CF set on error
EAX = error code (81h invalid VMM handle)
--------E-21252E-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM v2.3+ - GET/SET VMM PARAMETERS
AX = 252Eh
CL = direction (00h get parameters, 01h set parameters)
DS:EBX -> parameter buffer (see #0558)
Return: CF clear if successful
CF set on error
EAX = error code (81h bad parameter value)

Format of Phar Lap VMM parameter buffer:
Offset Size Description (Table 0558)
00h DWORD flags
bit 0: page fault logging enabled
---v5.0+ ---
bit 1: swap extender to disk during DOS EXEC call
bit 2: don't zero allocated memory
04h DWORD scan period for page aging, in milliseconds
08h DWORD maximum size (in bytes) to check on each page scan
0Ch 52 BYTEs unused
--------E-21252F-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v3.0 - WRITE RECORD TO VMM PAGE LOG FILE
AX = 252Fh
DS:EBX -> data to be written
CX = size of data in bytes
Return: CF clear if successful
CF set on error
EAX = error code (85h no page log file or not 386/VMM)
--------E-212530-----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v2.3+ - SET SIZE OF BUFFER FOR DOS CALLS
AX = 2530h
ECX = size of data buffer in bytes (1024 to 65536)
Return: CF clear if successful
CF set on error
EAX = error code
08h insufficient low memory
81h invalid size
SeeAlso: AX=2517h
--------E-212531-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender VMM v3.0 - READ/WRITE LDT DESCRIPTOR
AX = 2531h
BX = segment selector
ECX = direction (00h read, 01h write)
DS:EDX -> 8-byte buffer for descriptor contents
Return: CF clear if successful
CF set on error
EAX = error code
81h invalid selector
82h DPMI running, or not a code or data segment
--------E-212532-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - 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)
Notes: this call is also supported by the FlashTek X-32VM extender
this function is incompatible with 386|VMM; use AX=2522h instead
SeeAlso: AX=2522h,AX=2533h
--------E-212533-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - 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)
Notes: this call is also supported by the FlashTek X-32VM extender
this function is incompatible with 386|VMM; use AX=2522h instead
SeeAlso: AX=2522h,AX=2532h
--------E-212534-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender v3.0+ - GET INTERRUPT FLAG
AX = 2534h
Return: CF clear
EAX = interrupt state (00h disabled, 01h enabled)
--------E-212535-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender v3.0+ - READ/WRITE SYSTEM REGISTERS
AX = 2535h
EBX = direction (00h read registers, 01h write)
DS:EDX -> system register record (see #0559)
Return: CF clear
Note: this call is only available under MS Windows if PHARLAP.386 VDD is
installed

Format of Phar Lap system register record:
Offset Size Description (Table 0559)
00h DWORD CR0
04h 4 DWORDs DR0,DR1,DR2,DR3
14h 2 DWORDs reserved
1Ch 2 DWORDs DR6,DR7
24h 3 DWORDs reserved
--------E-212536----------------------------
INT 21 P - Phar Lap 386/DOS-Ext VMM v3.0+ - MIN/MAX EXTENDED/CONV MEMORY USAGE
AX = 2536h
EBX = bit flags
bit 0: modifying conventional memory rather than extended memory
bit 1: setting maximum memory usage rather than minimum
ECX = new limit in 4K pages
Return: CF clear if successful
EAX = new limit
CF set on error
EAX = error code (08h memory error or -NOPAGE set)
EBX = maxi