Ritchie is best remembered for developing the C programming language and countless programming mainstays such as the simple “hello, world” program that is used in just about every programming textbook made since.
Since its creation in 1973, the C programming language has become one of the most widely used programming languages in the history of computer science. It was designed to be, and is generally used as a programming language for systems programming (i.e. operating systems and embedded systems) because it is a very low level language that is incredibly fast and stable. It has also become the basis for numerous other languages, both in theory and practice, as languages such as Python and PHP are written in C.
Let’s not forget about his other huge contribution to humanity with the Unix operating system (which happens to be programmed in C). Initially, Unix was built in assembly language, but was converted to C by the time that language was released to the public. Over the years numerous operating systems have been developed using Unix as a foundation, including BSD, Solaris (Sun Microsystems), and the Mac OS X line. While it is not directly built on the Unix system, Linux derives most of its core principles from Unix.
Ritchie was apparently a brilliant programmer in practice as well as in theory. According to an NYTimes article, “Colleagues who worked with Mr. Ritchie were struck by his code – meticulous, clean and concise.” Which is most likely one of the reasons others could so easily implement C and Unix for so many uses other that for what they were initially intended. He will always be remembered as one of the fathers of modern computer science.