Snacc is short for "sample neufeld asn.1 to c compiler" and asn.1 stands for abstract syntax notation one (itu-t x.208/iso 8824). snacc supports a subset of asn.1 1988. if you need features of asn.1 1992 or later, snacc is not for you.

the documentation for snacc in postscript format and latex sources.