COFF

File Format
Name	COFF
Ontology	Electronic File Formats Executables COFF
Extension(s)	.o

The Common Object File Format (COFF) is a format used for object code and executables. It was originally developed for UNIX System V by AT&T. It was intended as a replacement for a.out, adding features like shared libraries and relocation records, but it was shortly after replaced by the ELF format. The COFF format has many incompatible extensions.

The Portable Executable format is based on COFF. COFF is also the native object format of the DJGPP toolchain; executables produced by it are COFF files with an MZ stub prepended.

References

• Texas Instruments has a nice overview of the COFF format
• Since DJGPP uses a variant of COFF, they also have a summary available here