What happens if a disk image is damaged before it gets to you? Does it contain file integrity information?

If a disk image is damaged before it gets to us, it is basically impossible that we will not know about it.

Contributors are requested to upload disk images archived by ZIP which provides a CRC32 integrity check on each file. However, if an error somehow escaped ZIP (however unlikely), the disk images must still pass at least 84 * 4 CRC32 checks done by the analyser. There is a CRC32 on each Track, for compressed and uncompressed data. There is a CRC32 for signal data compressed and uncompressed. There is also chunk headers explaining the chunk entries belonging to tracks so it is possibly 84 * 6 checks or more.

If any of these checks fail, we would not use the image and ask you to upload it again or redump the disk as needed.

Of tens-of-thousands of disk images contributed an error has escaped the ZIP CRC checks only a handful of times 1), and in each case it was immediately apparent by the analyser complaining about it.

1) Nearly all of these damaged files were actually caused by a faulty version of ZIP on Unix that corrupted files.