Watford Disk File System

The Watford DFS uses the same structure as Acorn's DFS with some additional attributes:

In byte 6 of Sector 1, bit 2 is clear and 3 is clear for Acorn & WDFS for disks up to 256K, but set for WDFS and disks larger than 256K.

Watford DFS use 19-bit file lengths and 11-bit sector numbers making the largest possible disk being 512K and the largest file size of 512K-1.

The disk layout is identical to Acorn DFS with some differences shown below:

Byte	Track 0 Sector 0								Track 0 Sector 1
Byte	7	6	5	4	3	2	1	0	7	6	5	4	3	2	1	0
0		First 8 characters of volume title padded with NULs or spaces								Last 4 characters of volume title padded with NULs or spaces
1
2
3
4									BCD catalogue cycle number
5									Number of files
6											Boot Opts		0	108
7									7	Sectors in volume						0
8		File name padded with spaces							7	Load address						0	Last file
9									15	Load address						8
10									7	Execution address						0
11									15	Execution address						8
12									7	File length						0
13	18Len								15	File length						8
14	10Sect								17 16 Exec		17 16		17 16 Load		9 8
15	Lk.	Directory							7	Start sector						0
16		File name padded with spaces							7	Load address						0	Second to last file
17									15	Load address						8
18									7	Execution address						0
19									15	Execution address						8
20									7	File length						0
21	18Len								15	File length						8
22	10Sect								17 16 Exec		17 16		17 16 Load		9 8
23	Lk.	Directory							7	Start sector						0

Sector 1 byte 6 bit 3 is always 0 like Acorn DFS
Sector 1 byte 6 bit 2 is bit 10 of the disk size / sectors in volume. 0=max 256K, 1=max 512K
Len in byte 5 of the filename is bit 18 of the File Length.
Len in byte 6 of the filename is bit 10 of the Start Sector.
Lk. in byte 7 is the same as for Acorn DFS

This section is based loosely on the following:

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