High Quality Content by WIKIPEDIA articles! Berkeley Yacc is a reimplementation of the Unix parser generator Yacc, originally written by Robert Corbett in 1990. It has the advantages of being written in ANSI C and being public domain software. Unix (officially trademarked as UNIX, sometimes also written as Unix with small caps) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna. Today's Unix systems are split into various branches, developed over time by AT&T as well as various commercial vendors and non-profit organizations.