Catalog files are basically a filesystem; each one contains a large set of (usually related) files. Number of file entries. File entries. Contents of the files. For a given index, the contents start at entry[idx].offset, and are entry[idx].length long. Name of the file. Always in 8.3 format. Padded with nulls if the filename is shorter. Timestamp of when the file was added to the archive. This might be something else, but all the values in a single cat file are very close together. a00c.cat has a timestamp about a minute before e00c.cat, and this field is about 0x40 (64) higher in e00c.cat. That would imply it's a number of seconds since an epoch. Additionally, einfo.cat (timestamped half a year earlier) has numbers much smaller. Epoch seems to be around 3/1/1979, although I could be mistaken. 1/1/1980 would make more sense. Length of the contents. Offset to the contents.