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ZDOS File Descriptor
DFS File Descriptor
NDOS/DDOS File Descriptor
| ZDOS File Descriptor | ||
|---|---|---|
| Byte(s) in Sector Decimal, Hex |
Byte(s) in OPEN Buffer Decimal |
Explanation |
| 0...3 | Reserved for future expansion | |
| 4, 5 | File ID Unused |
|
| 6, 7 | 2-byte pointer (disk address) to directory sector holding entry for this file | |
| 8, 9 | 2-byte pointer (disk address) to first data record of file Sector address of the first sector on disk. So the OS can walk forward through the file. |
|
| 10, 11 0aH, 0bH |
2-byte pointer (disk address) to last data record of file Sector address of the last sector on disk. So the OS can walk backward through the file. |
|
| 12 0cH |
0 | File Type and Subtype This value can be changed using the SET utility. |
| 13, 14 0dH, 0eH |
1, 2 | Record Count Number of data records. The sector of the file descriptor does not count here. |
| 15, 16 0fH, 10H |
3, 4 | Record Length A logical record can consist of 1, 2, 4, 8, 16 or 32 physical sectors. This results in record lengths of 80H, 100H, 200H, 400H, 800H or 1000H.
Default Record Length is 80H (128 bytes).Note: In UDOS-1526 (V4.x) the maximum Record Length is 800H
(16 sectors) because the disks have only 26 sectors per track. |
| 17, 18 11H, 12H |
5, 6 | Block Length Unused and set to be same as Record Length |
| 19 13H |
7 | File Properties This value can be changed using the SET utility. |
| 20, 21 14H, 15H |
8, 9 | Procedure files (Filetype=P) only - Starting execution address (ENTRY_POINT),
unused for other file types. This value can be changed using the SET utility. |
| 22, 23 16H, 17H |
10, 11 | Text files (Filetype=A) only - Number of bytes in the last record of the file This value can be changed using the SET utility. |
| 24...31 18H...1fH |
12...19 | Date of Creation |
| 32...39 20H...27H |
20...27 | Date of Last Write |
| 40...43 44...47 ...... 100...103 28H...67H |
28...31 32...35 ...... 88...91 |
Procedure files (Filetype=P) only - Segment descriptors for up to 16 code segments. Each segment descriptor is 4 bytes - the first 2 bytes are the starting address (loading address) of the segment and the second 2 bytes are the length of the segment in bytes. After the the last used segment descriptor is a null descriptor with each of the 4 bytes are zero. |
| 104...121 68H...79H |
92...109 | Unused |
| 122, 123 7aH, 7bH |
110, 111 | Procedure files (Filetype=P) only - Lowest segment starting address (LOW_ADDRESS) LOW_ADDRESS and HIGH_ADDRESS are used when loading the program files for allocating the main memory with MEMMGR. This value can be changed using the SET utility. |
| 124, 125 7cH, 7dH |
112, 113 | Procedure files (Filetype=P) only - Highest segment ending address rounded up to the end of the record (HIGH_ADDRESS) This value can be changed using the SET utility. |
| 126, 127 7eH, 7fH |
114, 115 | Procedure files (Filetype=P) only - Stacksize (STACK_SIZE) The size of the stack for the program the OS has to allocate at program load with MEMMGR. This value can be changed using the SET utility. |
The Zilog Hard Disk File System (DFS) has a slightly different structure of the file descriptor as the ZDOS. The number of sectors on hard disk may be greater than 65536. So we need a 3-byte pointer to address physical sectors. The OS and utilities are adjusted accordingly.
| DFS File Descriptor | ||
|---|---|---|
| Byte(s) in Sector Decimal, Hex |
Byte(s) in OPEN Buffer Decimal |
Explanation |
| 0...3 | Reserved for future expansion | |
| 4...7 | File ID | |
| 8...10 08H...0aH |
3-byte pointer (disk address) to directory sector holding entry for this file | |
| 11...13 0bH...0dH |
3-byte pointer (disk address) to first data record of file Sector address of the first sector on disk. So the OS can walk forward through the file. |
|
| 14...16 0eH...10H |
3-byte pointer (disk address) to last data record of file Sector address of the last sector on disk. So the OS can walk backward through the file. |
|
| 17 11H |
0 | File Type and Subtype This value can be changed using the SET utility. |
| 18, 19 12H, 13H |
1, 2 | Record Count Number of data records. The sector of the file descriptor does not count here. |
| 20, 21 14H, 15H |
3, 4 | Record Length - always 200H (512 bytes)In DFS, there are no variable record length. A logical record always has the same size as a physical sector. |
| 22, 23 16H, 17H |
5, 6 | Block Length Unused and set to be same as Record Length |
| 24 18H |
7 | File Properties This value can be changed using the SET utility. |
| 25, 26 19H, 1aH |
8, 9 | Procedure files (Filetype=P) only - Starting execution address (ENTRY_POINT),
unused for other file types. This value can be changed using the SET utility. |
| 27, 28 1bH, 1cH |
10, 11 | Text files (Filetype=A) only - Number of bytes in the last record of the file This value can be changed using the SET utility. |
| 29...36 1dH...24H |
12...19 | Date of Creation |
| 37...44 25H...2cH |
20...27 | Date of Last Write |
| 45...48 49...52 ...... 105...108 2dH...6cH |
28...31 32...35 ...... 88...91 |
Procedure files (Filetype=P) only - Segment descriptors for up to 16 code segments. Each segment descriptor is 4 bytes - the first 2 bytes are the starting address (loading address) of the segment and the second 2 bytes are the length of the segment in bytes. After the the last used segment descriptor is a null descriptor with each of the 4 bytes are zero. |
| 109...126 6dH...7eH |
92...109 | Unused |
| 127, 128 7fH, 80H |
110, 111 | Procedure files (Filetype=P) only - Lowest segment starting address (LOW_ADDRESS) LOW_ADDRESS and HIGH_ADDRESS are used when loading the program files for allocating the main memory with MEMMGR. This value can be changed using the SET utility. |
| 129, 130 81H, 82H |
112, 113 | Procedure files (Filetype=P) only - Highest segment ending address rounded up to the end of the record (HIGH_ADDRESS) This value can be changed using the SET utility. |
| 131, 132 83H, 84H |
114, 115 | Procedure files (Filetype=P) only - Stacksize (STACK_SIZE) The size of the stack for the program the OS has to allocate at program load with MEMMGR. This value can be changed using the SET utility. |
| 133...511 85H...1ffH |
Available for programmer definition | |
In German UDOS systems with NDOS or DDOS as filesystem the physical sector length
is 100H (256 bytes). The file descriptor has a size of 256 bytes.
| NDOS/DDOS File Descriptor | ||
|---|---|---|
| Byte(s) in Sector Decimal, Hex |
Byte(s) in OPEN Buffer Decimal |
Explanation |
| 0...11 00H...0bH |
Identical to ZDOS | |
| 12...14 0cH...0eH |
0...2 | Identical to ZDOS |
| 15, 16 0fH, 10H |
3, 4 | Record Length A logical record can consist of 0.5 (a half sector), 1, 2, 4, 8 or 16 physical sectors. This results in record lengths of 80H, 100H, 200H, 400H, 800H or 1000H.
Default Record Length is 100H (256 bytes).Note: The record length of 80H (128 bytes)
is maintained for compatibility reasons.
This means that only the half of the capacity of each physical sector is used.
RL=80 is implemented in NDOS only, not in DDOS. |
| 17...127 11H...7fH |
5...115 | Identical to ZDOS |
| 128, 129 80H, 81H |
2-byte pointer (disk address) to the pointer sector of this file | |
| 130...255 82H...0ffH |
Unused | |
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ZDOS File Descriptor
DFS File Descriptor
NDOS/DDOS File Descriptor