Dennis Ritchie, a veteran of Bell Labs and the principal developer, died Wednesday at his home in New Jersey.

In the late 1960s and early ’70s, working at Bell Labs, Mr. Ritchie made a pair of lasting contributions to computer science. He was the principal designer of the C programming language and co-developer of the Unix operating system, working closely with Ken Thompson, his longtime Bell Labs collaborator.

The C language is widely used in the development, embedded systems and operating systems. Unix was developed as an assembly language in 1969, but was recoded in C around 1973. Ritchie had been in poor health for some time. He was 70.