The ELF (Executable Linkable Format) was designed by SUN for use in their Unix clone. A very versatile file format, it was later picked up by many other operating systems for use as both executable files and as shared library files. It does distinguish between TEXT, DATA and BSS.
Documentation on ELF can be obtained e.g. at
http://www.linuxbase.org/spec/refspecs/elf/,
ftp://tsx.mit.edu/pub/linux/packages/GCC/ELF.doc.tar.gz, or various other sources.
Today, ELF is considered the standard format on Unix-alike systems. While it has some drawbacks (e.g., using up one of the scarce general purpose registers of the IA32 when using position-independent code), it is well supported and documented.
Operating Systems that use it: Solaris, IRIX and IRIX64, Linux, *BSD, many many others...
