a general-purpose parser generator
Edit by : Bison is a general-purpose Parser Generator that converts an annotated context-free grammar into an LALR(1) or GLR parser for that grammar. Once you are proficient with Bison, you can use it to develop a wide range of language parsers, from those used in simple desk calculators to complex programming languages.

Bison is upward compatible with YACC: all properly-written Yacc grammars ought to work with Bison with no change. Anyone familiar with Yacc should be able to use Bison with Little trouble. You need to be fluent in C or C++ programming in order to use Bison. you can free download Bison 2.3 now.