On Dec 26, 14:35, Nico de Jong wrote: system, the some be good The single-density "DFS" format is particularly easy. It consists of 10 sectors of 256 bytes per track, numbered 0 to 9, and is nominally single-sided. If you have doubled-sided drives, side 0 of the first drive is referred to as drive 0, and the sector headers are just as you'd expect; the second side (side 1) is referred to as drive 2, and has the *same* sector headers (ie the "head" number is stored in the header as "0", not "1"). Drives can be either 40-track or 80-track; the only difference (apart from the number of tracks, obviously) is the size stored in the directory. Recording method is standard FM with an Index Mark. There's no sector-to-sector interleave on a track, but the start of each track is skewed by three sectors, compared to the previous one. The directory occupies the first two sectors of track 0, and is extremely simple. I can describe it if you like, or give you a 512-byte dump of the two sectors. The double-density "ADFS" format is a bit more complicated. There are several variations, but the BBC Micro (as opposed to the later Archimedes) supported "S" (small) format (40 track SS), "M" (medium) (40 track DS or 80 track SS), and "L" (80 track DS). The DS versions are a little unusual in that they use all of side 0 before using any of side 1, but the head numbers are what you'd expect (ie "0" for side 0 and "1" for side 1). Each track is 16 sectors of 256 bytes, numbered 0-15, no interleave, track-to-track skew of 9 (ie track one begins with sector 9, track 1 begins with 2, track 2 with 11, etc), standard MFM but normally *without* an Index Mark (though it shouldn't matter if you put one in). The directory's a bit more complicated becasue there's a proper free space map, and it's a hierarchical structure. -- Pete Peter Turnbull Network Manager University of York