Dennis Ritchie was an influential American computer scientist best known for creating the C programming language and co-developing the Unix operating system. Born on September 9, 1941, he made significant contributions to the field of computer science, which have had a lasting impact on software development and operating systems. Ritchie's work on C provided a powerful and flexible programming language that is still widely used today. His collaboration on Unix helped shape modern computing environments, leading to the development of many other operating systems. Ritchie passed away on October 12, 2011, leaving behind a legacy that continues to influence technology.