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FCB
Format of File Control Block:
| Offset | Size | Description |
|---|---|---|
| 00h | BYTE | drive number (0 = default, 1 = A, etc) |
| FFh is not allowed (signals extended FCB, see XFCB) | ||
| 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 FILEDATE) |
| 16h | WORD | time of last write (see FILETIME) |
| 18h | 8 BYTEs | reserved |
| 20h | BYTE | record within current block |
| 21h | DWORD | random access record number (if record size is > 64 bytes, high byte is omitted) |
Notes
reserved field have different meaning in different DOSes. Not known is it used by OS/2 MVM.