Rational Software
Rational Machines was an enterprise founded by Paul Levy and Mike [Devlin (entrepreneur)|Mike Devlin] in 1981 to provide tools to expand the use of modern software engineering practices, particularly explicit modular architecture and Iterative and [incremental development|iterative development]. It changed its name in 1994 to Rational Software, and was sold for US$2.1 billion to IBM on February 21, 2003.