The Preferred Executable Format is a file format that specifies the format of executable files and other object code. PEF executables are also called Code Fragment Manager files (CFM).
PEF was developed by Apple Computer for use in its Mac OS operating system. It was optimised for RISC processors. In Mac OS X, the Mach-O file format is the native executable format. However, PEF is still supported on PowerPC-based Macintoshes and is used by some Carbon applications ported from earlier Mac OS versions.
BeOS on PowerPC systems also uses PEF, although x86 systems do not.