In the late 1950's, John Backus and Peter Naur developed a notation for describing the syntax (grammar) of programming languages. This notation is known as Backus-Naur Form (or BNF), and was first used in the Algol 60 Report  to specify the syntax of Algol 60, and has since been used for specifying the syntax of other programming languages.
A few years earlier, in 1956, the linguist Chomsky had published  an article about a hierarchy of formal grammatical systems for describing various classes of languages. Even though expressed very differently, and developed independently, it turns out that BNF is logically equivalent to Chomsky's level 2 grammar (often referred to as a context-free grammar).
- Revised Report on the Algorithmic Language Algol 60. Retrieved on 2012-05-11.
- Chomsky, Noam (1956). "Three models for the description of language". IRE Transactions on Information Theory 2: 113–124. http://www.chomsky.info/articles/195609--.pdf. Retrieved 2012-05-11.