This is Bruce Evans' C compiler and binutils package. Either the compiler as the assembler are able to generate 16-bit code. Hence it's possible to compile BIOS and DOS code under Unix. The C compiler does understand K&R1 syntax, with a few restrictions regarding bit fields. See the file work/bcc/bcc-cc1/bcc.bugs for Bruce's bug list. The binutils (assembler and loader) have been renamed to as86 and ld86 to not conflict with the system's assembler and loader, but they are also available in the regular BINDIR (normally /usr/local/bin). It's also possible to generate MC 6809 code with bcc/as. (This is a compile-time option however, and not supported by the binary package as it comes with FreeBSD.)