What goes into a file header?

Question

I keep wondering "what goes info a file header" and all I can find is "what goes into a C header file" which is not what I want, I want to know what goes into for example a tarball's or an ELF executable's header, anything generic or does it depend per file type?

Answer 1

Depends per file type, they sit as a data specification known as "file format specification" and somewhat proprietary registered (example .exe). Best example is EXIF image headers. It heavily coincides data and data transfer specifications can be found throughout IETF rfc's.