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AH = 52h
Return:
ES:BX -> DOS list of lists (see #01627)
Notes: Partially supported by OS/2 v1.1 compatibility box (however, most pointers are FFFFh:FFFFh, LASTDRIVE is FFh, and the NUL header "next" pointer is FFFFh:FFFFh).. Partially supported by the Windows NT DOS box; contains only a rudimentary Current Directory Structure (see #01645). On return, ES points at the DOS data segment (see also INT 2F/AX=1203h). Quarterdeck's suggested check for the use of its DOSDATA.SYS or DOS-UP.SYS is to test whether the list-of-lists segment is greater than the segment of the first memory block; a better check for DOS-UP.SYS is INT 21/AX=2B01h/CX=444Dh. Because not all DOS workalikes support all fields in the List of Lists, applications should ensure that pointers are neither 0000h:0000h nor FFFFh:FFFFh before using them. Windows for Workgroups 3.11 network and Windows95 set the path to the local drive and directory even for network drives; in that case the UNC form \\SERVER\SHARE can be obtained with INT 21/AX=5F02h or INT 21/AX=5F46h. LapLink RemoteAccess does the same even for INT 21/AX=5F02h. Windows95 GUI no longer returns the true path for a SUBSTed drive, but MS-DOS 7.00 does; use INT 21/AH=60h to obtain the true name
See Also: INT 2F/AX=1203h
Format of List of Lists: Offset Size Description (Table 01627) -24 WORD (DOS 3.1+) contents of CX from INT 21/AX=5E01h -22 WORD (DOS ???+) LRU counter for FCB caching -20 WORD (DOS ???+) LRU counter for FCB opens -18 DWORD (DOS ???+) address of OEM function handler (see INT 21/AH=F8h) FFFFh:FFFFh if not installed or not available -14 WORD (DOS ???+) offset in DOS CS of code to return from INT 21 call -12 WORD (DOS 3.1+) sharing retry count (see AX=440Bh) -10 WORD (DOS 3.1+) sharing retry delay (see AX=440Bh) -8 DWORD (DOS 3.0+) pointer to current disk buffer -4 WORD (DOS 3.0+) pointer in DOS data segment of unread CON input when CON is read via a handle, DOS reads an entire line, and returns the requested portion, buffering the rest for the next read. 0000h indicates no unread input -2 WORD segment of first memory control block (see #01628) 00h DWORD pointer to first Drive Parameter Block (see #01395 at AH=32h) 04h DWORD -> first System File Table (see #01639,#01640,#01641,#01642) 08h DWORD pointer to active CLOCK$ device's header (most recently loaded driver with CLOCK bit set) 0Ch DWORD pointer to active CON device's header (most recently loaded driver with STDIN bit set) ---DOS 2.x--- 10h BYTE number of logical drives in system 11h WORD maximum bytes/block of any block device 13h DWORD pointer to first disk buffer (see #01649,#01650) 17h 18 BYTEs actual NUL device driver header (not a pointer!) NUL is always the first device on DOS's linked list of device drivers. (see #01646) ---DOS 3.0--- 10h BYTE number of block devices 11h WORD maximum bytes/block of any block device 13h DWORD pointer to first disk buffer (see #01650,#01652) 17h DWORD pointer to array of current directory structures (see #01643) 1Bh BYTE value of LASTDRIVE command in CONFIG.SYS (default 5) 1Ch DWORD pointer to STRING= workspace area 20h WORD size of STRING area (the x in STRING=x from CONFIG.SYS) 22h DWORD pointer to FCB table 26h WORD the y in FCBS=x,y from CONFIG.SYS 28h 18 BYTEs actual NUL device driver header (not a pointer!) NUL is always the first device on DOS's linked list of device drivers. (see #01646) ---DOS 3.1-3.3--- 10h WORD maximum bytes per sector of any block device 12h DWORD pointer to first disk buffer in buffer chain (see #01650) 16h DWORD pointer to array of current directory structures (see #01643) 1Ah DWORD pointer to system FCB tables (see #01640,#01641,#01642) 1Eh WORD number of protected FCBs (the y in the CONFIG.SYS FCBS=x,y) 20h BYTE number of block devices installed 21h BYTE number of available drive letters (largest of 5, installed block devices, and CONFIG.SYS LASTDRIVE=). Also size of current directory structure array. 22h 18 BYTEs actual NUL device driver header (not a pointer!) NUL is always the first device on DOS's linked list of device drivers. (see #01646) 34h BYTE number of JOIN'ed drives ---DOS 4.x--- 10h WORD maximum bytes per sector of any block device 12h DWORD pointer to disk buffer info record (see #01652,#01653)
Note: Although the initialization code in IO.SYS uses this pointer, MSDOS.SYS does not, instead using the hardcoded address of the info record 16h DWORD pointer to array of current directory structures (see #01643,#01644) 1Ah DWORD pointer to system FCB tables (see #01640,#01641,#01642) 1Eh WORD number of protected FCBs (the y in the CONFIG.SYS FCBS=x,y) (always 00h for DOS 5.0) 20h BYTE number of block devices installed 21h BYTE number of available drive letters; also size of current directory structure array.
For DOS 4.0-6.0:
Largest of 5, installed block devices, and CONFIG.SYS LASTDRIVE= For DOS 7.x (Windows9X), set to 32 if no LASTDRIVE= or LASTDRIVEHIGH=, else set to larger of installed block devices and LASTDRIVE(HIGH)= 22h 18 BYTEs actual NUL device driver header (not a pointer!) NUL is always the first device on DOS's linked list of device drivers. (see #01646) 34h BYTE number of JOIN'ed drives 35h WORD pointer within IBMDOS code segment to list of special program names (see #01662) (always 0000h for DOS 5.0) 37h DWORD pointer to FAR routine for resident IFS utility functions (see #01658) may be called by any IFS driver which does not wish to service functions 20h or 24h-28h itself 3Bh DWORD pointer to chain of IFS (installable file system) drivers 3Fh WORD the x in BUFFERS x,y (rounded up to multiple of 30 if in EMS) 41h WORD number of lookahead buffers (the y in BUFFERS x,y) 43h BYTE boot drive (1=A:)44h BYTE flag:
01h to use DWORD moves (80386+), 00h otherwise 45h WORD extended memory size in KB ---DOS 5.0-6.0--- 10h 39 BYTEs as for DOS 4.x (above) 37h DWORD pointer to SETVER program list or 0000h:0000h 3Bh WORD (DOS=HIGH) offset in DOS CS of function to fix A20 control when executing special .COM format 3Dh WORD PSP of most-recently EXECed program if DOS in HMA, 0000h if low used for maintaining count of INT 21 calls which disable A20 on return 3Fh 8 BYTEs as for DOS 4.x (above) ---Windows NT DOS Box--- 10h 6 BYTEs ??? 16h DWORD pointer to array of current directory structures (see #01645) 1Ah 6 BYTEs ??? 20h BYTE number of block devices installed 21h BYTE number of local drive letters (= installed block devices) Also size of current directory structure array. 22h 18 BYTEs actual NUL device driver header (not a pointer!) NUL is always the first device on DOS's linked list of device drivers. (see #01646) ---DOS 7.x--- 10h 55 BYTEs as for DOS 5.0-6.0 (above) 47h 25 BYTEs ??? 60h BYTE "DOS_FLAG" (see also INT 26)Format of DOS memory control block: Offset Size Description (Table 01628)
00h BYTE block type:
5Ah if last block in chain, otherwise 4Dh 01h WORD PSP segment of owner or special flag value (see #01629) 03h WORD size of memory block in paragraphs 05h 3 BYTEs unused by MS-DOS (386MAX) if locked-out block, region start/prev region end ---DOS 2.x,3.x--- 08h 8 BYTEs unused ---DOS 4.0+ --- 08h 8 BYTEs ASCII program name if PSP memory block or DR DOS UMB, else garbage null-terminated if less than 8 characters
Notes: The next MCB is at segment (current + size + 1). Under DOS 3.1+, the first memory block is the DOS data segment, containing installable drivers, buffers, etc. Under DOS 4.0+ it is divided into subsegments, each with its own memory control block (see #01633), the first of which is at offset 0000h.. For DOS 5+, blocks owned by DOS may have either "SC" or "SD" in bytes 08h and 09h. "SC" is system code or locked-out inter-UMB memory, "SD" is system data, device drivers, etc.. Some versions of DR DOS use only seven characters of the program name, placing a NUL in the eighth byte.
See Also: #01630 - #01632 - #01633
(Table 01629) Values for special flag PSP segments: 0000h free 0006h DR DOS XMS UMB 0007h DR DOS excluded upper memory ("hole") 0008h belongs to DOS FFF7h 386MAX v6.01+ ??? FFFAh 386MAX UMB control block (see #01477 at AX=4402h"386MAX") FFFDh 386MAX locked-out memory FFFEh 386MAX UMB (normally immediately follows its control block) FFFFh 386MAX v6.01+ device driver
Format of MS-DOS 5+ UMB control block: Offset Size Description (Table 01630)
00h BYTE type:
5Ah if last block in chain, 4Dh otherwise 01h WORD first available paragraph in UMB if control block at start of UMB, 000Ah if control block at end of UMB 03h WORD length in paragraphs of following UMB or locked-out region 05h 3 BYTEs unused08h 8 BYTEs block type name:
"UMB" if start block, "SM" if end block in UMB
See Also: #01628 - #01631
Format of MS-DOS 7.0 HMA memory control block: Offset Size Description (Table 01631) 00h WORD signature "MS" (4Dh 53h) 02h WORD usage flag??? 0000h free else ??? 04h WORD size of memory block in bytes (not counting MCB) 06h WORD offset of next memory block in HMA or 0000h 08h 8 BYTEs unused (0)
See Also: #01628 - #01630 - #01632
Format of STARLITE (General Software's Embedded DOS) memory control block: Offset Size Description (Table 01632)
00h BYTE block type:
5Ah if last block in chain, otherwise 4Dh 01h WORD PSP segment of owner, 0000h if free, 0008h if belongs to DOS 03h WORD size of memory block in paragraphs 05h BYTE unused 06h WORD segment address of next memory control block (0000h if last) 08h WORD segment address of previous memory control block or 0000h 0Ah 6 BYTEs reservedFormat of DOS 4.0+ data segment subsegment control blocks: Offset Size Description (Table 01633) 00h BYTE subsegment type (blocks typically appear in this order) "D" device driver "E" device driver appendage "I" IFS (Installable File System) driver (MS-DOS 7) high-loaded drive data table array (see #02603) "F" FILES= control block storage area (for FILES>5) "X" FCBS= control block storage area, if present "C" BUFFERS EMS workspace area (if BUFFERS /X option used) "B" BUFFERS= storage area "L" LASTDRIVE= current directory structure array storage area "S" STACKS= code and data area, if present (see #01634,#01635) "T" INSTALL= transient code 01h WORD paragraph of subsegment start (usually the next paragraph) 03h WORD size of subsegment in paragraphs 05h 3 BYTEs unused 08h 8 BYTEs for types "D" and "I", base name of file from which the driver was loaded (unused for other types)
Format of data at start of STACKS code segment (if present): Offset Size Description (Table 01634) 00h WORD ??? 02h WORD number of stacks (the x in STACKS=x,y) 04h WORD size of stack control block array (should be 8*x) 06h WORD size of each stack (the y in STACKS=x,y) 08h DWORD pointer to STACKS data segment 0Ch WORD offset in STACKS data segment of stack control block array 0Eh WORD offset in STACKS data segment of last element of that array 10h WORD offset in STACKS data segment of the entry in that array for the next stack to be allocated (initially same as value in 0Eh and works its way down in steps of 8 to the value in 0Ch as hardware interrupts pre-empt each other)
Note: The STACKS code segment data may, if present, be located as follows:
DOS 3.2:
The code segment data is at a paragraph boundary fairly early in the IBMBIO segment (seen at 0070:0190h)DOS 3.3:
The code segment is at a paragraph boundary in the DOS data segment, which may be determined by inspecting the segment pointers of the vectors for those of interrupts 02h, 08h-0Eh, 70h, 72-77h which have not been redirected by device drivers or TSRs. DOS 4.0+ Identified by sub-segment control block type "S" within the DOS data segment.
See Also: #01636 - INT B4"STACKMAN"
Format of array elements in STACKS data segment: Offset Size Description (Table 01635)
00h BYTE status:
00h=free, 01h=in use, 03h=corrupted by overflow of higher stack. 01h BYTE not used 02h WORD previous SP 04h WORD previous SS 06h WORD ptr to word at top of stack (new value for SP). The word at the top of the stack is preset to point back to this control block.Format of SHARE.EXE hooks (DOS 3.1-6.00): Offset Size Description (Table 01636) (offsets from first system file table--pointed at by ListOfLists+04h) -3Ch DWORD pointer to FAR routine for ???
Note: Not called by MS-DOS 3.3, set to 0000h:0000h by SHARE 3.3+ -38h DWORD pointer to FAR routine called on opening file on call, internal DOS location points at filename (see #01687 at AX=5D06h)
Return:
CF clear if successful CF set on error AX = DOS error code (24h) (see #01680 at AH=59h/BX=0000h)
Note: SHARE directly accesses DOS-internal data to get name of file just opened -34h DWORD pointer to FAR routine called on closing file ES:DI -> system file table
Note: Does something to every Record Lock Record for file -30h DWORD pointer to FAR routine to close all files for given computer (called by AX=5D03h) -2Ch DWORD pointer to FAR routine to close all files for given process (called by AX=5D04h) -28h DWORD pointer to FAR routine to close file by name (called by AX=5D02h) DS:SI -> DOS parameter list (see #01686 at AX=5D00h) DPL's DS:DX -> name of file to close
Return:
CF clear if successful CF set on error AX = DOS error code (03h) (see #01680 at AH=59h/BX=0000h) -24h DWORD pointer to FAR routine to lock region of file call with BX = file handle ---DOS 3.x--- CX:DX = starting offset SI:AX = size ---DOS 4.0+ --- DS:DX -> lock range DWORD start offset DWORD size in bytesReturn:
CF set on error AL = DOS error code (21h) (see #01680 at AH=59h)
Note: Not called if file is marked as remote -20h DWORD pointer to FAR routine to unlock region of file call with BX = file handle ---DOS 3.x--- CX:DX = starting offset SI:AX = size ---DOS 4.0+ --- DS:DX -> lock range DWORD start offset DWORD size in bytes
Return:
CF set on error AL = DOS error code (21h) (see #01680 at AH=59h)
Note: Not called if file is marked as remote -1Ch DWORD pointer to FAR routine to check if file region is locked call with ES:DI -> system file table entry for file CX = length of region from current position in file
Return:
CF set if any portion of region locked AX = 0021h -18h DWORD pointer to FAR routine to get open file list entry (called by AX=5D05h) call with DS:SI -> DOS parameter list (see #01686 at AX=5D00h) DPL's BX = index of sharing record DPL's CX = index of SFT in SFT chain of sharing recReturn:
CF set on error or not loaded AX = DOS error code (12h) (see #01680 at AH=59h) CF clear if successful ES:DI -> filename CX = number of locks owned by specified SFT BX = network machine number DX destroyed -14h DWORD pointer to FAR routine for updating FCB from SFT??? call with DS:SI -> unopened FCB ES:DI -> system file table entryReturn:
BL = C0h???
Note: Copies following fields from SFT to FCB: starting cluster of file 0Bh 1Ah sharing record offset 33h 1Ch file attribute 04h 1Eh -10h DWORD pointer to FAR routine to get first cluster of FCB file ??? call with ES:DI -> system file table entry DS:SI -> FCB
Return:
CF set if SFT closed or sharing record offsets mismatched CF clear if successful BX = starting cluster number from FCB -0Ch DWORD pointer to FAR routine to close file if duplicate for process DS:SI -> system file tableReturn:
AX = number of handle in JFT which already uses SFT
Note: Called during open/create of a file
Note: If SFT was opened with inheritance enabled and sharing mode 111, does something to all other SFTs owned by same process which have the same file open mode and sharing record -08h DWORD pointer to FAR routine for closing file
Note: Closes various handles referring to file most-recently opened -04h DWORD pointer to FAR routine to update directory info in related SFT entries call with ES:DI -> system file table entry for file (see #01641) AX = subfunction (apply to each related SFT)
00h:
Update time stamp (offset 0Dh) and date stamp (offset 0Fh)01h:
Update file size (offset 11h) and starting cluster (offset 0Bh). Sets last-accessed cluster fields to start of file if file never accessed02h:
As function 01h, but last-accessed fields always changed03h:
Do both functions 00h and 02h
Note: Follows ptr at offset 2Bh in system file table entries
Note: NOP if opened with no-inherit or via FCB
Notes: Most of the above hooks (except -04h, -14h, -18h, and -3Ch) assume either that SS=DOS DS or SS=DS=DOS DS and directly access DOS-internal data. Sharing hooks are not supported by DR DOS 5-6; they appear to be supported by Novell DOS 7, with a segment of 0000h indicating the DOS data segment
See Also: #01637 - #01638
Format of sharing record: Offset Size Description (Table 01637) 00h BYTE flag 00h free block 01h allocated block FFh end marker 01h WORD size of block 03h BYTE checksum of pathname (including NUL) if sum of ASCII values is N, checksum is (N/256 + N%256) 04h WORD offset in SHARE's DS of first Record Lock Record (see #01638) 06h DWORD pointer to start of system file table chain for file 0Ah WORD unique sequence number 0Ch var ASCIZ full pathname
Note: Not supported by DR DOS SHARE 1.1 and 2.0; will reportedly be supported by Novell DOS 7
See Also: #01636 - #01638
Format of SHARE.EXE Record Lock Record: Offset Size Description (Table 01638) 00h WORD offset in SHARE's DS of next lock table in list or 0000h 02h DWORD offset in file of start of locked region 06h DWORD offset in file of end of locked region 0Ah DWORD pointer to System File Table entry for this file 0Eh WORD PSP segment of lock's owner ---DOS 5+ ---
10h WORD lock type:
(00h lock all, 01h lock writes only)
See Also: #01636 - #01637 - #01639 - #01642
Format of DOS 2.x system file tables: Offset Size Description (Table 01639) 00h DWORD pointer to next file table (offset FFFFh if last) 04h WORD number of files in this table 06h 28h bytes per file. Offset Size Description 00h BYTE number of file handles referring to this file 01h BYTE file open mode (see #01402 at AH=3Dh) 02h BYTE file attribute 03h BYTE drive (0 = character device, 1 = A, 2 = B, etc) 04h 11 BYTEs filename in FCB format (no path,no period,blank-padded) 0Fh WORD ??? 11h WORD ??? 13h DWORD file size??? 17h WORD file date in packed format (see #01666 at AX=5700h) 19h WORD file time in packed format (see #01665 at AX=5700h) 1Bh BYTE device attribute (see #01423 at AX=4400h). ---character device--- 1Ch DWORD pointer to device driver. ---block device--- 1Ch WORD starting cluster of file 1Eh WORD relative cluster in file of last cluster accessed. ------ 20h WORD absolute cluster number of current cluster 22h WORD ??? 24h DWORD current file position???
See Also: #01640 - #01641 - #01642
Format of DOS 3.0 system file tables and FCB tables: Offset Size Description (Table 01640) 00h DWORD pointer to next file table (offset FFFFh if last) 04h WORD number of files in this table 06h 38h bytes per file. Offset Size Description 00h-1Eh as for DOS 3.1+ (see #01641) 1Fh WORD byte offset of directory entry within sector 21h 11 BYTEs filename in FCB format (no path/period, blank-padded) 2Ch DWORD (SHARE.EXE) pointer to previous SFT sharing same file 30h WORD (SHARE.EXE) network machine number which opened file (Windows Enhanced mode DOSMGR uses the virtual machine ID as the machine number; see INT 2F/AX=1683h) 32h WORD PSP segment of file's owner (first three entries for AUX/CON/PRN contain segment of IO.SYS startup code) 34h WORD (SHARE.EXE) offset in SHARE code seg of share record 36h WORD ??? apparently always 0000h
See Also: #01639 - #01641 - #01642
Format of DOS 3.1-3.3x, DR DOS 5.0-6.0 system file tables and FCB tables: Offset Size Description (Table 01641) 00h DWORD pointer to next file table (offset FFFFh if last) 04h WORD number of files in this table 06h 35h bytes per file. Offset Size Description 00h WORD number of file handles referring to this file 02h WORD file open mode (see AX=6C00h, #01402 at AH=3Dh) bit 15 set if this file opened via FCB 04h BYTE file attribute (see #01420 at AX=4301h) 05h WORD device info word (see #01423 at AX=4400h) bit 15 set if remote file bit 14 set means do not set file date/time on closing bit 12 set means don't inherit on EXEC bits 5-0 drive number for disk files 07h DWORD pointer to device driver header if character device else pointer to DOS Drive Parameter Block (see #01395 at AH=32h) 0Bh WORD starting cluster of file 0Dh WORD file time in packed format (see #01665 at AX=5700h) not used for character devices in DR DOS 0Fh WORD file date in packed format (see #01666 at AX=5700h) not used for character devices in DR DOS 11h DWORD file size. ---system file table--- 15h DWORD current offset in file (may be larger than size of file; INT 21/AH=42h does not check new position). ---FCB table--- 15h WORD counter for last I/O to FCB 17h WORD counter for last open of FCB (these are separate to determine the times of the latest I/O and open). --- 19h WORD relative cluster within file of last cluster accessed 1Bh WORD absolute cluster number of last cluster accessed 0000h if file never read or written??? 1Dh WORD number of sector containing directory entry (see #01352) 1Fh BYTE number of dir entry within sector (byte offset/32) 20h 11 BYTEs filename in FCB format (no path/period, blank-padded) 2Bh DWORD (SHARE.EXE) pointer to previous SFT sharing same file 2Fh WORD (SHARE.EXE) network machine number which opened file (Windows Enhanced mode DOSMGR uses the virtual machine ID as the machine number; see INT 2F/AX=1683h) 31h WORD PSP segment of file's owner (see #01378 at AH=26h) (first three entries for AUX/CON/PRN contain segment of IO.SYS startup code) 33h WORD offset within SHARE.EXE code segment of sharing record (see #01637) 0000h = none
See Also: #01639 - #01640 - #01642
Format of DOS 4.0-6.0 system file tables and FCB tables: Offset Size Description (Table 01642) 00h DWORD pointer to next file table (offset FFFFh if last) 04h WORD number of files in this table 06h 3Bh bytes per file. Offset Size Description 00h WORD number of file handles referring to this file FFFFh if in use but not referenced 02h WORD file open mode (see AX=6C00h,#01402 at AH=3Dh) bit 15 set if this file opened via FCB 04h BYTE file attribute (see #01420 at AX=4301h) 05h WORD device info word (see also #01423 at AX=4400h) bit 15 set if remote file bit 14 set means do not set file date/time on closing bit 13 set if named pipe bit 12 set if no inherit bit 11 set if network spooler bit 7 set if device, clear if file (only if local) bits 6-0 as for AX=4400h 07h DWORD pointer to device driver header if character device else pointer to DOS Drive Parameter Block (see #01395 at AH=32h) or REDIR data 0Bh WORD starting cluster of file (local files only) not set for FAT32-capable versions of Windows95 (since they allow 32-bit cluster numbers) 0Dh WORD file time in packed format (see #01665) 0Fh WORD file date in packed format (see #01666) 11h DWORD file size 15h DWORD current offset in file (SFT) LRU counters (FCB table, two WORDs). ---local file--- 19h WORD relative cluster within file of last cluster accessed 1Bh DWORD number of sector containing directory entry 1Fh BYTE number of dir entry within sector (byte offset/32). ---network redirector--- 19h DWORD pointer to REDIRIFS record 1Dh 3 BYTEs ???. ------ 20h 11 BYTEs filename in FCB format (no path/period, blank-padded) 2Bh DWORD (SHARE.EXE) pointer to previous SFT sharing same file 2Fh WORD (SHARE.EXE) network machine number which opened file (Windows Enhanced mode DOSMGR uses the virtual machine ID as the machine number; see INT 2F/AX=1683h) 31h WORD PSP segment of file's owner (see #01378 at AH=26h) (first three entries for AUX/CON/PRN contain segment of IO.SYS startup code) 33h WORD offset within SHARE.EXE code segment of sharing record (see #01595) 0000h = none 35h WORD (local) absolute cluster number of last clustr accessed (redirector) ??? 37h DWORD pointer to IFS driver for file, 0000000h if native DOS
Note: The OS/2 2.0 DOS Boot Session does not properly fill in the filename field due to incomplete support for SFTs; the OS/2 2.0 DOS Window does not appear to support SFTs at all
See Also: #01639 - #01640 - #01641
Format of current directory structure (CDS) (array, LASTDRIVE entries): Offset Size Description (Table 01643) 00h 67 BYTEs ASCIZ path in form X:\PATH (local) or UNC form \\SERVER\PATH (network, see notes below) 43h WORD drive attributes (also see note below) (see also AX=5F07h)
bit 15:
Uses network redirector \ invalid if 00, installablebit 14:
Physical drive / file system if 11bit 13:
JOIN'ed \ path above is true path that would bebit 12:
SUBST'ed / needed if not under SUBST or JOINbit 11:
Removable media (WinNT4.0)bit 10:
Hard disk??? (WinNT4.0)bit 7:
Remote drive hidden from redirector's assign-list and exempt from network connection make/break commands; set for CD-ROM drives by MSCDEX (not supported by CORELCDX) 45h DWORD pointer to Drive Parameter Block for drive (see #01395 at AH=32h) ---local drives--- 49h WORD starting cluster of current directory 0000h = root, FFFFh = never accessed 4Bh WORD ??? seems to be FFFFh always 4Dh WORD ??? seems to be FFFFh always ---network drives--- 49h DWORD pointer to redirector or REDIRIFS record, or FFFFh:FFFFh (DOS 4 only) available for use by IFS driver 4Dh WORD stored user data from INT 21/AX=5F03h ------ 4Fh WORD offset in current directory path of backslash corresponding to root directory for drive this value specifies how many characters to hide from the "CHDIR" and "GETDIR" calls; normally set to 2 to hide the drive letter and colon, SUBST, JOIN, and networks change it so that only the appropriate portion of the true path is visible to the user ---DOS 4.0+ --- 51h BYTE (DOS 4 only, remote drives) device type 04h network drive 52h DWORD pointer to IFS driver (DOS 4) or redirector block (DOS 5+) for this drive, 00000000h if native DOS 56h WORD available for use by IFS driver
Notes: The path for invalid drives is normally set to X:\, but may be empty
after JOIN x:
/D in DR DOS 5.0 or NET USE x: /D in older LAN versions. Normally, only one of bits 13&12 may be set together with bit 14, butDR DOS 5.0 uses other combinations for bits 15-12:
0111 JOIN, 0001 SUBST, 0101 ASSIGN (see #01644). Windows for Workgroups 3.11 network sets the path to the local drive and directory even for network drives; in that case the UNC form \\SERVER\SHARE can be obtained with INT 21/AX=5F02h or INT 21/AX=5F46h. LapLink RemoteAccess does the same even for INT 21/AX=5F02h. Window NT 4.0 always uses X:\PATH, even for substituted drives (i.e. the CDS will *not* contain the original path prior to SUBST). SoftWindows on the Macintosh PowerPC sets \\E for the host drive
See Also: #01644 - INT 21/AX=71AAh/BL=00h
Format of DR DOS 5.0-6.0 current directory structure entry (array): Offset Size Description (Table 01644) 00h 67 BYTEs ASCIZ pathname of actual root directory for this logical drive 43h WORD drive attributes 1000h SUBSTed drive 3000h??? JOINed drive 4000h physical drive 5000h ASSIGNed drive 7000h JOINed drive 8000h network drive 45h BYTE physical drive number (0=A:) if this logical drive is valid 46h BYTE ??? apparently flags for JOIN and ASSIGN 47h WORD cluster number of start of parent directory (0000h = root) 49h WORD entry number of current directory in parent directory 4Bh WORD cluster number of start of current directory 4Dh WORD used for media change detection (details not available) 4Fh WORD cluster number of SUBST/JOIN "root" directory 0000h if physical root directory
See Also: #01643
Format of Windows NT Current Directory Structure (CDS) (array): Offset Size Description (Table 01645) 00h 67 BYTEs ASCIZ path in form X:\ (does not show either current directory or network path) 43h 4 BYTEs ???
Note: The WinNT CDS contains only as many entries as there are local drives, not LASTDRIVE entries.
Format of DOS device driver header: Offset Size Description (Table 01646) 00h DWORD pointer to next driver, offset=FFFFh if last driver 04h WORD device attributes (see #01647,#01648) 06h WORD device strategy entry point call with ES:BX -> request header (see #02597 at INT 2F/AX=0802h) 08h WORD device interrupt entry point ---character device--- 0Ah 8 BYTEs blank-padded character device name ---block device--- 0Ah BYTE number of subunits (drives) supported by driver 0Bh 7 BYTEs normally unused; sometimes contains signature to indicate specific drivers: "$PCMATA" PCMCIA driver PCMATA.SYS (see AX=440Dh"DOS 3.2+") "AHADDVR" Adaptec SCSI disk driver ASPIDISK.SYS "DBLSPAC" MS DoubleSpace or DriveSpace "DSKREET" NortonUtils v5+ Diskreet (see INT 2F/AX=FE00h) "GFS " LapLink III device driver DD.BIN "SIDExxx" PCMCIA driver ATADRV.EXE (see AX=440Dh"DOS 3.2+") "STAC-CD" Stacker/Stacker Anywhere (see AX=4404h"Stacker") ---DoubleSpace/DriveSpace--- 12h 2 BYTEs signature ",." (2Ch 2Eh) 14h var preloading API entry point ---CD-ROM--- 12h WORD reserved, must be 0000h appears to be another device chain 14h BYTE drive letter, 01h=A:, etc. (must initially be 00h; this byte is set by MSCDEX when it loads) 15h BYTE number of units 16h 6 BYTEs signature 'MSCDnn' where 'nn' is version (currently '00') (this field does not exist in most drivers)
See Also: #02550 at INT 25/AX=CDCDh - #02845 at INT 2F/AX=5600h
Bitfields for device attributes (character device): Bit(s) Description (Table 01647) 15 set (indicates character device) 14 IOCTL supported (see AH=44h) 13 (DOS 3.0+) output until busy supported 12 reserved 11 (DOS 3.0+) OPEN/CLOSE/RemMedia calls supported 10-8 reserved 7 (DOS 5.0+) Generic IOCTL check call supported (driver command 19h). (see AX=4410h,AX=4411h) 6 (DOS 3.2+) Generic IOCTL call supported (driver command 13h). (see AX=440Ch,AX=440Dh"DOS 3.2+") 5 reserved 4 device is special (use INT 29 "fast console output") 3 device is CLOCK$ (all reads/writes use transfer record described below) 2 device is NUL 1 device is standard output 0 device is standard input
Note: For European MS-DOS 4.0, bit 11 also indicates that bits 8-6 contain a version code (000 = DOS 3.0,3.1; 001 = DOS 3.2; 010 = European DOS 4.0)
See Also: #01648 - #01646
Bitfields for device attributes (block device): Bit(s) Description (Table 01648) 15 clear (indicates block device) 14 IOCTL supported 13 non-IBM format 12 network device (device is remote) 11 (DOS 3.0+) OPEN/CLOSE/RemMedia calls supported 10 reserved 9 direct I/O not allowed??? (set by DOS 3.3 DRIVER.SYS for "new" drives) 8 ??? set by DOS 3.3 DRIVER.SYS for "new" drives 7 (DOS 5.0+) Generic IOCTL check call supported (driver command 19h). (see AX=4410h,AX=4411h) 6 (DOS 3.2+) Generic IOCTL call supported (driver command 13h). Implies support for commands 17h and 18h (see AX=440Ch,AX=440Dh"DOS 3.2+",AX=440Eh,AX=440Fh) 5-2 reserved 1 driver supports 32-bit sector addressing (DOS 3.31+) 0 reserved
Note: For European MS-DOS 4.0, bit 11 also indicates that bits 8-6 contain a version code (000 = DOS 3.0,3.1; 001 = DOS 3.2; 010 = European DOS 4.0)
See Also: #01647 - #01646
Format of DOS 2.x disk buffer: Offset Size Description (Table 01649) 00h DWORD pointer to next disk buffer, offset = FFFFh if last least-recently used buffer is first in chain 04h BYTE drive (0=A, 1=B, etc), FFh if not in use 05h 3 BYTEs unused??? (seems always to be 00h 00h 01h) 08h WORD logical sector number 0Ah BYTE number of copies to write (1 for non-FAT sectors) 0Bh BYTE sector offset between copies if multiple copies to be written 0Ch DWORD pointer to DOS Drive Parameter Block (see #01395 at AH=32h) 10h buffered data
See Also: #01650 - #01652 - #01653 - #01655
Format of DOS 3.x disk buffer: Offset Size Description (Table 01650) 00h DWORD pointer to next disk buffer, offset = FFFFh if last least-recently used buffer is first in chain 04h BYTE drive (0=A,1=B, etc), FFh if not in use 05h BYTE buffer flags (see #01651) 06h WORD logical sector number 08h BYTE number of copies to write (1 for non-FAT sectors) 09h BYTE sector offset between copies if multiple copies to be written 0Ah DWORD pointer to DOS Drive Parameter Block (see #01395 at AH=32h) 0Eh WORD unused??? (almost always 0) 10h buffered data
See Also: #01649 - #01652 - #01653 - #01655
Bitfields for DOS 3.x disk buffer flags: Bit(s) Description (Table 01651) 7 ??? 6 buffer dirty 5 buffer has been referenced 4 ??? 3 sector in data area 2 sector in a directory, either root or subdirectory 1 sector in FAT 0 boot sector??? (guess)
See Also: #01656
Format of DOS 4.00 (pre UR 25066) disk buffer info: Offset Size Description (Table 01652) 00h DWORD pointer to array of disk buffer hash chain heads (see #01654) 04h WORD number of disk buffer hash chains (referred to as NDBCH below) 06h DWORD pointer to lookahead buffer, zero if not present 0Ah WORD number of lookahead sectors, else zero (the y in BUFFERS=x,y) 0Ch BYTE 00h if buffers in EMS (/X), FFh if not 0Dh WORD EMS handle for buffers, zero if not in EMS 0Fh WORD EMS physical page number used for buffers (usually 255) 11h WORD ??? seems always to be 0001h 13h WORD segment of EMS physical page frame 15h WORD ??? seems always to be zero 17h 4 WORDs EMS partial page mapping information???
See Also: #01649 - #01650 - #01653 - #01657
Format of DOS 4.01 (from UR 25066 Corrctive Services Disk on) disk buffer info: Offset Size Description (Table 01653) 00h DWORD pointer to array of disk buffer hash chain heads (see #01654) 04h WORD number of disk buffer hash chains (referred to as NDBCH below) 06h DWORD pointer to lookahead buffer, zero if not present 0Ah WORD number of lookahead sectors, else zero (the y in BUFFERS=x,y) 0Ch BYTE 01h, possibly to distinguish from pre-UR 25066 format 0Dh WORD ??? EMS segment for BUFFERS (only with /XD) 0Fh WORD ??? EMS physical page number of EMS seg above (only with /XD) 11h WORD ??? EMS segment for ??? (only with /XD) 13h WORD ??? EMS physical page number of above (only with /XD) 15h BYTE ??? number of EMS page frames present (only with /XD) 16h WORD segment of one-sector workspace buffer allocated in main memory if BUFFERS/XS or /XD options in effect, possibly to avoid DMA into EMS 18h WORD EMS handle for buffers, zero if not in EMS 1Ah WORD EMS physical page number used for buffers (usually 255) 1Ch WORD ??? appears always to be 0001h 1Eh WORD segment of EMS physical page frame 20h WORD ??? appears always to be zero 22h BYTE 00h if /XS, 01h if /XD, FFh if BUFFERS not in EMS
See Also: #01649 - #01650 - #01652 - #01657
Format of DOS 4.x disk buffer hash chain head (array, one entry per chain): Offset Size Description (Table 01654) 00h WORD EMS logical page number in which chain is resident, -1 if not in EMS 02h DWORD pointer to least recently used buffer header. All buffers on this chain are in the same segment. 06h BYTE number of dirty buffers on this chain 07h BYTE reserved (00h)
Notes: Buffered disk sectors are assigned to chain N where N is the sector's address modulo NDBCH, 0 <= N <= NDBCH-1. Each chain resides completely within one EMS page. This structure is in main memory even if buffers are in EMS
Format of DOS 4.0-6.0 disk buffer: Offset Size Description (Table 01655) 00h WORD forward ptr, offset only, to next least recently used buffer 02h WORD backward pointer, offset only 04h BYTE drive (0=A,1=B, etc) if bit 7 clear SFT index if bit 7 set FFh if not in use 05h BYTE buffer flags (see #01656) 06h DWORD logical sector number (local buffers only) 0Ah BYTE number of copies to write for FAT sectors, same as number of FATs for data and directory sectors, usually 1 0Bh WORD offset in sectors between copies to write for FAT sectors 0Dh DWORD pointer to DOS Drive Parameter Block (see #01395 at AH=32h) 11h WORD size of data in buffer if remote buffer (see also #01656) 13h BYTE reserved (padding) 14h buffered data
Note: For DOS 4.x, all buffered sectors which have the same hash value (computed as the sum of high and low words of the logical sector number divided by the number of disk buffer chains) are on the same doubly-linked circular chain; for DOS 5+, only a single circular chain exists.. The links consist of offset addresses only, the segment being the same for all buffers in the chain.
See Also: #01649 - #01650 - #01652
Bitfields for DOS 4.0-6.0 disk buffer flags: Bit(s) Description (Table 01656) 7 remote buffer 6 buffer dirty 5 buffer has been referenced (reserved in DOS 5+) 4 search data buffer (only valid if remote buffer) 3 sector in data area 2 sector in a directory, either root or subdirectory 1 sector in FAT 0 reserved
See Also: #01651
Format of DOS 5.0-6.0 disk buffer info: Offset Size Description (Table 01657) 00h DWORD pointer to least-recently-used buffer header (may be in HMA) (see #01655) 04h WORD number of dirty disk buffers 06h DWORD pointer to lookahead buffer, zero if not present 0Ah WORD number of lookahead sectors, else zero (the y in BUFFERS=x,y) 0Ch BYTE buffer location 00h base memory, no workspace buffer 01h HMA, workspace buffer in base memory 0Dh DWORD pointer to one-segment workspace buffer in base memory 11h 3 BYTEs unused 14h WORD ???
16h BYTE flag:
INT 24 fail while making an I/O status call 17h BYTE temp storage for user memory allocation strategy during EXEC18h BYTE counter:
Number of INT 21 calls for which A20 is off 19h BYTE bit flagsbit 0:
???bit 1:
SWITCHES=/W specified in CONFIG.SYS (don't load WINA20.SYS when MS Windows 3.0 starts)bit 2:
In EXEC state (INT 21/AX=4B05h) 1Ah WORD offset of unpack code start (used only during INT 21/AX=4B05h) 1Ch BYTE bit 0 set iff UMB MCB chain linked to normal MCB chain 1Dh WORD minimum paragraphs of memory required by program being EXECed 1Fh WORD segment of first MCB in upper memory blocks or FFFFh if DOS memory chain in base 640K only (first UMB MCB usually at 9FFFh, locking out video memory with a DOS-owned memory block) the MCB this word points at contains a valid link into high memory even if it is marked with a 'Z' indicating the last memory block 21h WORD paragraph from which to start scanning during memory allocation
See Also: #01652 - #01653
(Table 01658) Call IFS utility function entry point with:. AH = 20h miscellaneous functions AL = 00h get date
Return:
CX = year DH = month DL = day AL = 01h get process ID and computer IDReturn:
BX = current PSP segment DX = active network machine number AL = 05h get file system info ES:DI -> 16-byte info bufferReturn:
Buffer filled Offset Size Description 00h 2 BYTEs unused 02h WORD number of SFTs (actually counts only the first two file table arrays) 04h WORD number of FCB table entries 06h WORD number of proctected FCBs 08h 6 BYTEs unused 0Eh WORD largest sector size supported AL = 06h get machine name ES:DI -> 18-byte buffer for nameReturn:
Buffer filled with name starting at offset 02h AL = 08h get sharing retry countReturn:
BX = sharing retry count AL = otherReturn:
CF set. AH = 21h get redirection state BH = type (03h disk, 04h printer)Return:
BH = state (00h off, 01h on). AH = 22h ??? some sort of time calculation AL = 00h ??? nonzero ???. AH = 23h ??? some sort of time calculation. AH = 24h compare filenames DS:SI -> first ASCIZ filename ES:DI -> second ASCIZ filenameReturn:
ZF set if files are same ignoring case and / vs \. AH = 25h normalize filename DS:SI -> ASCIZ filename ES:DI -> buffer for resultReturn:
Filename uppercased, forward slashes changed to backslashes. AH = 26h get DOS stackReturn:
DS:SI -> top of stack CX = size of stack in bytes. AH = 27h increment InDOS flag. AH = 28h decrement InDOS flag
Note: IFS drivers which do not wish to implement functions 20h or 24h-28h may pass them on to the default handler pointed at by [LoL+37h]
See Also: #01659 - #01660
Format of IFS driver list: Offset Size Description (Table 01659) 00h DWORD pointer to next driver header 04h 8 BYTEs IFS driver name (blank padded), as used by FILESYS command 0Ch 4 BYTEs ??? 10h DWORD pointer to IFS utility function entry point (see #01658) call with ES:BX -> IFS request (see #01660) 14h WORD offset in header's segment of driver entry point. ???
See Also: #01658 - #01660
Format of IFS request block: Offset Size Description (Table 01660) 00h WORD total size in bytes of request 02h BYTE class of request 02h ??? 03h redirection 04h ??? 05h file access 06h convert error code to string 07h ??? 03h WORD returned DOS error code 05h BYTE IFS driver exit status 00h success 01h ??? 02h ??? 03h ??? 04h ??? FFh internal failure 06h 16 BYTEs ??? ---request class 02h--- 16h BYTE function code 04h ??? 17h BYTE unused??? 18h DWORD pointer to ??? 1Ch DWORD pointer to ??? 20h 2 BYTEs ??? ---request class 03h--- 16h BYTE function code 17h BYTE ??? 18h DWORD pointer to ??? 1Ch DWORD pointer to ??? 22h WORD returned ??? 24h WORD returned ??? 26h WORD returned ??? 28h BYTE returned ??? 29h BYTE unused??? ---request class 04h--- 16h DWORD pointer to ??? 1Ah DWORD pointer to ??? ---request class 05h--- 16h BYTE function code 01h flush disk buffers 02h get disk space 03h MKDIR 04h RMDIR 05h CHDIR 06h delete file 07h rename file 08h search directory 09h file open/create 0Ah LSEEK 0Bh read from file 0Ch write to file 0Dh lock region of file 0Eh commit/close file 0Fh get/set file attributes 10h printer control 11h ??? 12h process termination 13h ???. ---class 05h function 01h--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h 4 BYTEs ??? 26h BYTE ??? 27h BYTE ???. ---class 05h function 02h--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h 4 BYTEs ??? 26h WORD returned total clusters 28h WORD returned sectors per cluster 2Ah WORD returned bytes per sector 2Ch WORD returned available clusters 2Eh BYTE returned ??? 2Fh BYTE ???. ---class 05h functions 03h,04h,05h--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h 4 BYTEs ??? 26h DWORD pointer to directory name. ---class 05h function 06h--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h 4 BYTEs ??? 26h WORD attribute mask 28h DWORD pointer to filename. ---class 05h function 07h--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h 4 BYTEs ??? 26h WORD attribute mask 28h DWORD pointer to source filespec 2Ch DWORD pointer to destination filespec. ---class 05h function 08h--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h 4 BYTEs ??? 26h BYTE 00h FINDFIRST 01h FINDNEXT 28h DWORD pointer to FindFirst search data + 01h if FINDNEXT 2Ch WORD search attribute if FINDFIRST 2Eh DWORD pointer to filespec if FINDFIRST. ---class 05h function 09h--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h DWORD pointer to IFS open file structure (see #01661) 26h WORD ??? \ together, specify open vs. create, whether or 28h WORD ??? / not to truncate 2Ah 4 BYTEs ??? 2Eh DWORD pointer to filename 32h 4 BYTEs ??? 36h WORD file attributes on call returned ??? 38h WORD returned ???. ---class 05h function 0Ah--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h DWORD pointer to IFS open file structure (see #01661) 26h BYTE seek type (02h = from end) 28h DWORD offset on call returned new absolute position. ---class 05h functions 0Bh,0Ch--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h DWORD pointer to IFS open file structure (see #01661) 28h WORD number of bytes to transfer returned bytes actually transferred 2Ah DWORD transfer address. ---class 05h function 0Dh--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h DWORD pointer to IFS open file structure (see #01661) 26h BYTE file handle??? 27h BYTE unused??? 28h WORD ??? 2Ah WORD ??? 2Ch WORD ??? 2Eh WORD ???. ---class 05h function 0Eh--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h DWORD pointer to IFS open file structure (see #01661) 26h BYTE 00h commit file 01h close file 27h BYTE unused???. ---class 05h function 0Fh--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h 4 BYTEs ??? 26h BYTE 02h GET attributes 03h PUT attributes 27h BYTE unused??? 28h 12 BYTEs ??? 34h WORD search attributes??? 36h DWORD pointer to filename 3Ah WORD (GET) returned ??? 3Ch WORD (GET) returned ??? 3Eh WORD (GET) returned ??? 40h WORD (GET) returned ??? 42h WORD (PUT) new attributes (GET) returned attributes. ---class 05h function 10h--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h DWORD pointer to IFS open file structure (see #01661) 26h WORD ??? 28h DWORD pointer to ??? 2Ch WORD ??? 2Eh BYTE ??? 2Fh BYTE subfunction 01h get printer setup 03h ??? 04h ??? 05h ??? 06h ??? 07h ??? 21h set printer setup. ---class 05h function 11h--- 17h 7 BYTEs ??? 1Eh DWORD pointer to ??? 22h DWORD pointer to IFS open file structure (see #01661) 26h BYTE subfunction 27h BYTE unused??? 28h WORD ??? 2Ah WORD ??? 2Ch WORD ??? 2Eh BYTE ??? 2Fh BYTE ???. ---class 05h function 12h--- 17h 15 BYTEs unused??? 26h WORD PSP segment 28h BYTE type of process termination 29h BYTE unused???. ---class 05h function 13h--- 17h 15 BYTEs unused??? 26h WORD PSP segment ---request class 06h--- 16h DWORD returned pointer to string corresponding to error code at 03h 1Ah BYTE returned ??? 1Bh BYTE unused ---request class 07h--- 16h DWORD pointer to IFS open file structure (see #01661) 1Ah BYTE ??? 1Bh BYTE unused???
See Also: #01659 - #01658 - #01661
Format of IFS open file structure: Offset Size Description (Table 01661) 00h WORD ??? 02h WORD device info word 04h WORD file open mode 06h WORD ??? 08h WORD file attributes 0Ah WORD owner's network machine number 0Ch WORD owner's PSP segment 0Eh DWORD file size 12h DWORD current offset in file 16h WORD file time 18h WORD file date 1Ah 11 BYTEs filename in FCB format 25h WORD ??? 27h WORD hash value of SFT address (low word of linear address + segment&F000h) 29h 3 WORDs network info from SFT 2Fh WORD ???
Format of one item in DOS 4.0+ list of special program names: Offset Size Description (Table 01662) 00h BYTE length of name (00h = end of list) 01h N BYTEs name in format name.ext N 2 BYTEs DOS version to return for program (major,minor) (see AH=30h,INT 2F/AX=122Fh) ---DOS 4 only--- N+2 BYTE number of times to return fake version number (FFh = always)
Note: If the name of the executable for the program making the DOS "get version" call matches one of the names in this list, DOS returns the specified version rather than the true version number
Category: DOS Kernel - Int 21h - D
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