Hi, Norman. >> The chain actually belongs to the header/map and map entry $F >> (containing $0000) is the last in the chain. > > Hmmm, see above. This is where I seem to lose the plot. Are you > saying that the zero block in the map, holding $0001 is telling me > (a) where on disc to find the 4 sectors for this block PLUS (b) > where the second block in this file is (ie, map entry $0001).
Hmm... the map chain is, perhaps, a bad example because it is not actually associated with a file. Consider the root directory: The medium header tells us that its first group number is $10, i.e. its first 4 sectors are sectors $40, $41, $42, $43 on the disk. If the $10-th entry in the map is zero, the directory is contained within those 4 sectors. If not, the map entry tells us its next group number, i.e. where its next 4 sectors are. For your disk, the $10-th map entry is $5c, so the 5th sector is sector $170 (since $5c*4 = $170) and the 8th sector is sector $173. If the directory is more than eight sectors in length, the $5c-th entry will be non-zero, and so on... For all other files, the first group number is, as you say, stored in the directory entry (offset $3a) for that file. John _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm
