They're just variants on the IFF theme.[1] All of these files are broken into chucks with a FourCC header (sometimes with letters alternately upper or lower case, depending on features and version) that includes a chunk length and occasionally a checksum. It's a very simple and flexible format that almost no one since the '90s seems to use any more for new file formats, the only exceptions being the likes of PNG, MPEG, and a couple other things.
[1] https://en.wikipedia.org/wiki/Interchange_File_Format