Johnson joined Bell Labs and AT&T in the 1960s and worked on Unix tools for nearly 20 years, alongside computer scientists like Jeffrey Ullman, Dennis Ritchie and Alfred Aho.
[4] Bell Labs colleague Alfred Aho suggested he look at Donald Knuth's work on LR parsing, which served as the basis for Yacc.
[1] Lint was developed in 1978 while Johnson was debugging the Yacc grammar he was writing for C and struggling with portability issues stemming from porting Unix to a 32-bit machine.
[2][5] In 1986, Johnson moved to Silicon Valley, where he joined several startups, where he worked mostly on compilers, but also 2D and 3D graphics, massively parallel computing and embedded systems.
[citation needed] In 2002, he moved to Boston to work at MathWorks,[7] where he helped maintain the front end of the MATLAB programming language, for which he also built a lint product called M-Lint.