Make your own free website on Tripod.com
Up ] Docs Home ]

Format of DOS 4.0-6.0 system file tables and FCB tables

Back ] Next ]

Offset Size Description

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