The Common Object File Format (COFF) is a specification of a format for executable, object code, and shared library computer files used on Unix systems. It was introduced in Unix System V, and formed the basis for extended specifications such as XCOFF and ECOFF, before being largely replaced by ELF, introduced with SVR4. COFF and its variants continue to be used on some Unix-like systems, on Microsoft Windows, and in EFI environments. See  COFF in Wikipedia for more information.

Yasm generates COFF format object files for use with DJGPP, which is 32bit DOS version of GCC.