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) |
reserved field have different meaning in different DOSes. Not known is it used by OS/2 MVM.
| SVC API | |
|---|---|
| Supervisor calls | 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 |
| Structures | FCB XFCB FILETIME FILEDATE |