Commodore Plus 4 - Page 413

DOS Error Messages 401
(23, 24, and 27) can be caused by improper grounding (e.g., you are not using a
three-prong outlet, your outlet is not properly grounded, etc.). Check that your
equipment is grounded properly if these errors occur. In general, if a diskette
causes errors that cannot be explained, you should make copies of all the
information on the diskette. Then, attempt to do a complete HEADER on the
diskette. If it is performed successfully, you can reuse the diskette. Otherwise, toss
it.
20 READ ERROR (header "block not found)
The header of the requested data block could not be located by the DOS.
Either an illegal sector number was specified, or the header block is corrupt.
21 READ ERROR (sync mark not found)
The sync mark of the requested track could not be located by the DOS. This
message can occur because of misalignment of the heads. Misalignment can
be a hardware problem or an improperly inserted diskette. This message can
also occur if no diskette is present or if the diskette is not formatted.
22 READ ERROR (data block not found)
The data read from the requested sector was corrupt. This can indicate an
illegal sector number request, or a corrupt sector.
23 READ ERROR (data "block checksum error)
The checksum read from the requested sector did not match the checksum of
its data. This can indicate a corrupt sector.
24 READ ERROR (data "block decoding error)
At least 1 byte of data read from the requested sector was corrupt. This can
indicate a corrupt sector.
25 WRITE ERROR (verification of data error)
When validated, the data byte just written to the diskette did not match the
data in memory. This can be caused by a physically damaged diskette. An
unclosed file will result. Perform a validate (COLLECT) operation to delete
the unclosed file.