HelpPC 2.10 Quick Reference Utility Copyright 1991 David Jurgens

                      System File Table  (Undocumented)

                       DOS 2.x System File Table Format

    Offset Size                Description

       00   dword      pointer to next system file table; offset of ffffh
                       indicates last table in chain
       04   word       number of file descriptors in table
       06  nbytes      file descriptor table of the format (40 bytes each):

    Offset Size                Description

       00   byte       count of handles referring to this file or
                       zero if file is no longer open
       01   byte       open mode
       02   byte       file attribute
       03   byte       drive (1=A, 2=B:, ..., 0=char device)
       04 11bytes      filename in FCB format
       0F   word       unknown
       11   word       unknown
       13   dword      file size
       17   word       file date
       19   word       file time
       1B   byte       device attribute
       1C   word       starting cluster of file (block device)
            dword      pointer to device driver (if char device)
       1E   word       if block device, relative cluster within file of
                       the last cluster read; zero if file has never
                       been read or written
       20   word       absolute cluster number of current cluster
       22   word       unknown
       24   dword      current file position


                DOS 3.x System File Table and FCB Table Format

    Offset Size                Description

       00   dword      pointer to next system file table; offset of ffffh
                       indicates last table in chain
       04   word       number of file descriptors in table
       06  nbytes      file descriptor table of the format (53 bytes each):

    Offset Size                Description

       00   word       count of handles referring to this file or
                       zero if file is no longer open
       02   word       open mode, bit 15 set if file id opened via FCB
       04   byte       file attribute
       05   word       device info word
       07   dword      if char device pointer to device driver header
                       if block device pointer to DOS Device Control Block
       0B   word       starting cluster of file
       0D   word       file time
       0F   word       file date
       11   dword      file size
       15   dword      current file position
       19   word       if block device, relative cluster within file of
                       the last cluster read
       1B   word       absolute cluster number of last cluster read
                       zero if file has never been read or written
       1D   word       sector number containing the directory entry
       1F   byte       number of dir entry within sector
       20 11bytes      filename in FCB format
       2B   dword      SHARE pointer to previous SFT sharing same file
       2F   word       SHARE number of network machine opening file
       31   word       PSP segment of file owner
       33   word       offset within SHARE code segment of sharing record
                       0000h = none


                   DOS 4.0+ System File Table and FCB Table

    Offset Size                Description

       00   dword      pointer to next system file table; offset of ffffh
                       indicates last table in chain
       04   word       number of file descriptors in table
       06  nbytes      file descriptor table of the format (59 bytes each):

    Offset Size                Description

       00   word       count of handles referring to this file or
                       zero if file is no longer open
       02   word       open mode, bit 15 set if file id opened via FCB
       04   byte       file attribute
       05   word       device info word
       07   dword      if char device pointer to device driver header
                       if block device pointer to DOS Device Control Block
                       or REDIR data
       0B   word       starting cluster of file
       0D   word       file time
       0F   word       file date
       11   dword      file size
       15   dword      current file position
       19   dword      if network redirector, pointer to REDIRIFS record
            word       if local block dev, relative cluster within file
                       of the last cluster read
       1B   dword      if local, sector number of directory entry
       1F   byte       if local, number of directory entry within sector
       20  11bytes     filename in FCB format
       2B   dword      SHARE pointer to previous SFT sharing same file
       2F   word       SHARE number of network machine opening file
       31   word       PSP segment of file owner
       33   word       offset within SHARE code seg of sharing record
                       0000h = none
       35   word       absolute cluster number of last cluster read
                       zero if file has never been read or written
       37   dword      pointer to file IFS driver, NULL if native DOS


       - these structures are allocated by DOS during the scanning of the
         CONFIG.SYS file
       - INT 21,67 can be used to allow an application to have more than
         20 file handles;  the total number of handles is limited still to
         the value of FILES=n in CONFIG.SYS
       - the structure of these fields is undocumented;  I do not recommend
         relying on any of this information, instead use it as an aid in
         debugging
       - see Bibliography references to Bernd Schemmer and "Data Structures
         Used in IBM PC Compatibles and the PS/2".
       - see   INT 21,52

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