🚀 go-pugleaf

If I format a disk double sided from the desktop, it will have 80
tracks of 9 sectors. One of these is the boot sector, and there are 2
copies of the Fat Allocation Table (5 sectors each) and a root
directory (7 sectors).

Now, 2*80*9-1-2*5-7 = 1422, and at 512 bytes per sector this is
728064 bytes. However, after formatting is complete (assuming no bad
sectors), I am told that the disk has 726016 bytes free. 2K is
unaccounted for.

Also, if I format a 720K disk on an MS-DOS machine, DOS reports 730112
bytes free (a FAT is only 3 sectors under DOS). If I take this same blank
disk and put it in my ST, a "show info" reports 728064 bytes free - another
error of 2048 bytes.

A Dfree() call on a TOS formatted disk suggests that the disk has 711
clusters of which 709 are free (yet again suggesting that 2K has been
used). I know that cluster numbers start at 2, but this isn't "used"
space.

Is this a TOS bug, or have I missed something? Anyone got any ideas?



Andrew Dawson
School Of Medicine Computer Unit
University College London