ATLEE@UMDC.BITNET (Dick Atlee) (01/13/89)
AHA! Dick Atlee may have sent me the answer to questions like "why
does APP385.2 unexpectedly halt at line 600" and the like.
I wonder if this particular bug infects any of Apple's later ProDOS
to DOS 3.3 copy utilities?
----------------------------Original message----------------------------
The CONVERT program which was available from the first menu on the old
ProDOS disk has a bug. Programs not large enough to fill up a track/sector
list will work fine. The problem comes when the track/sector list for a file
is full. At such a point, a second sector of track/sector information must
be started. This is done with no problem. However, the POINTER in the first
sector which indicates where this second sector is gets screwed up. The
TRACK number of the second sector is put in the SECTOR part of the pointer,
while the pointer's TRACK indicator is set to 0. So the pointer says
TRACK: 0 Sector: <track>
TRACK 0 is bad news on a DOS 3.3 disk, needless to say.
I discovered this when doing transfers of ProDOS files for users here at the
University of Maryland. Because the Maryland Kermit-A2 only handles DOS3.3, I
had to run CONVERT, and discovered that certain larger files would arbitrarily
stop (whether sending them or TYPEing them) with a kind of swishing of the
drive head. A lot of disk zapping produced the above conclusions.