In TheEvolutionOfTheUnixTimeSharingSystem, DennisRitchie credits KenThompson, DougMcIlroy, JoeOssanna and himself as the main people behind early UnixOperatingSystem development. Other contributors mentioned there include R. H. Canaday (who participated in the design of the filesystem) and BrianKernighan (who gets the credit for inventing the name). KenThompson is usually recognised as the leader of the initiative and the #1 inventor of Unix. DennisRitchie gets the credit for CeeLanguage and was Thompson's main collaborator on the operating system. DougMcIlroy was responsible for the inclusion of pipes.
JoeOssanna wrote nroff and troff (based on the design of an influential pre-Unix formatter, RUNOFF), which were essential to early Bell Labs adoption of Unix for internal use for patent filing.
KenThompson wrote the TextEditor ed (EdIsTheStandardTextEditor!!!), based on the pre-UNIX QED, and invented the important technique of on-the-fly interpretation of NDFAs (NonDeterministicFiniteAutomata?) for RegularExpression search, now widely adopted in text editors.