Berkeley Yacc was originated in 1985 by Robert Corbett (see Corbett 1984). It was originally named 「zoo」, but by October 1989 it became known as Berkeley Yacc or byacc.

Berkeley Yacc had three advantages over the ancestral Yacc: it generated faster parsers, it could generate reentrant parsers, and the source code was released to the public domain rather than being under an AT&T proprietary license. The better performance came from implementing techniques from DeRemer and Penello』s seminal paper on LALR parsing (see DeRemer 1982).

Use of byacc spread rapidly due to its public domain license. However, once Bison became available, byacc itself passed out of general use.

https://www.gnu.org/software/bison/manual/html_node/Byacc.html

Berkeley yacc parser generator

Berkeley yacc is a parser generator utility that reads a grammar specification from a file and generates an LR(1) parser for it. The parsers consist of a set of LALR(1) parsing tables and a driver routine written in the C programming language. It has a public domain license which includes the generated C.

This package is configured with backtracking enable which makes it reasonably compatible with GNU bison.

Note that for better compatibility with bison, byacc supports the --defines=<defines_file> and --output=<output_file> options as alternatives for -H <defines_file> and -o <output_file>. For example:

byacc --defines=parse.h --output=parse.c parse.y

Note also that the byacc executable provides build2 metadata.