Dennis MacAlistair Ritchie was born on September 9, 1941, and died around October 12, 2011. He was an American computer scientist who worked with his longtime colleague, Ken Thompson. Together, they developed the Unix operating system, the C programming language, and the B programming language.

Early life and education

Dennis Ritchie was born in Bronxville, New York. His father was Alistair E. Ritchie, a scientist who worked for Bell Labs for many years and helped write a book called The Design of Switching Circuits about switching circuit theory. When Dennis was a child, his family moved to Summit, New Jersey, where he completed high school. He studied physics and applied mathematics at Harvard University and graduated in 1963.

Career

In 1967, Ritchie started working at the Bell Labs Computing Science Research Center. In 1968, he finished a draft of his PhD thesis titled "Computational Complexity and Program Structure" at Harvard, with guidance from Patrick C. Fischer. However, Ritchie never officially received his PhD degree. In 2020, the Computer History Museum, along with Ritchie's and Fischer's families, discovered a copy of the missing dissertation.

During the 1960s, Ritchie and Ken Thompson worked on the Multics operating system at Bell Labs. Later, Thompson used an old PDP-7 machine to create his own application programs and operating system, with help from Ritchie and others. In 1970, Brian Kernighan proposed the name "Unix," a play on the name "Multics." To support assembly language with a system-level programming language, Thompson developed B. Later, B was replaced by C, created by Ritchie. Ritchie continued to work on Unix and C for many years.

In the 1970s, Ritchie worked with James Reeds and Robert Morris on a method to break secret messages from the M-209 US cipher machine, which could solve messages of at least 2000–2500 letters. Ritchie explained that after discussing with the National Security Agency, the authors chose not to publish their findings because the method could apply to machines still used by foreign governments.

Ritchie also helped develop the operating systems Plan 9 and Inferno, as well as the programming language Limbo.

As part of an AT&T restructuring in the mid-1990s, Ritchie moved to Lucent Technologies. He retired in 2007 as head of the System Software Research Department.

C and Unix

Dennis Ritchie created the C programming language. He was also one of the people who helped develop the Unix operating system. He wrote a book called The C Programming Language with Brian Kernighan. This book is often called K&R because of their initials. Ritchie worked with Ken Thompson, who wrote the first version of Unix. Ritchie helped move Unix to work on different types of computers and systems. Their influence on Research Unix was so great that Doug McIlroy later said, "The names of Ritchie and Thompson are likely connected to almost everything in Unix that is not otherwise credited."

Today, the C programming language is widely used for creating applications, operating systems, and embedded systems. Its influence can be seen in most modern programming languages. C is a low-level language, meaning its features closely match the instructions used by computer hardware. However, C is not tied to any specific hardware, which makes it easy to write programs that work on any computer that can run C. C is also a high-level language, with features that match data structures used in software applications.

C influenced other programming languages, including C++, Objective-C (used by Apple), C# (used by Microsoft), and Java (used in businesses and Android apps). Ritchie and Thompson used C to create Unix, which helped shape many computing ideas that are now widely used.

In a 1999 interview, Ritchie said that Linux and Berkeley Software Distribution (BSD) operating systems are based on Unix. He considered them to be extensions of Unix. He also said that Unix and Linux are "the continuation of ideas started by Ken and me, along with many others, many years ago."

Awards

In 1983, Ritchie and Thompson were given the Turing Award for creating ideas about generic operating systems and for building the UNIX operating system. Ritchie's speech at the award was called "Reflections on Software Research." In 1990, both Ritchie and Thompson received the IEEE Richard W. Hamming Medal from the Institute of Electrical and Electronics Engineers (IEEE) for creating the UNIX operating system and the C programming language.

In 1997, Ritchie and Thompson were honored as Fellows of the Computer History Museum for helping create the UNIX operating system and developing the C programming language.

On April 21, 1999, Thompson and Ritchie received the National Medal of Technology for co-inventing the UNIX operating system and the C programming language. The medal's citation said these inventions led to major progress in computer hardware, software, and networking systems and helped the computer industry grow, which strengthened American leadership in the Information Age.

In 2005, the Industrial Research Institute gave Ritchie an Achievement Award for his work on the Unix operating system and its impact on science, technology, and society.

In 2011, Ritchie and Thompson were awarded the Japan Prize for Information and Communications for their role in developing the Unix operating system.

Death

Dennis Ritchie passed away on October 12, 2011, at the age of 70 in his home in Berkeley Heights, New Jersey. He lived alone. The first announcement about his death was made by Rob Pike, a former coworker. For many years, Ritchie had struggled with poor health after receiving treatment for prostate cancer and heart disease. Reports about Ritchie's death received less attention because the media was focusing on the recent death of Steve Jobs, co-founder of Apple, which happened the week before.

Legacy

After Ritchie's death, computer historian Paul E. Ceruzzi shared his thoughts. Brian Kernighan, a longtime colleague, said in an interview that Ritchie never imagined C would become so important. Kernighan told The New York Times, "The tools Dennis created and their later versions are used in almost everything today." He also noted how C and Unix helped develop major projects, such as the iPhone. Other people highlighted Ritchie's influence on technology.

One person compared Ritchie's work to that of Steve Jobs, saying Ritchie's contributions were vital to the technological changes of the past 40 years, including the technology Apple used to build its success. Another person explained that Ritchie helped create two key software technologies that are found in nearly every computer program used today, directly or indirectly. Many in computer science and related fields recognized Ritchie's role in advancing computing.

The Fedora 16 Linux version, released about a month after Ritchie's death, was dedicated to his memory. FreeBSD 9.0, released on January 12, 2012, was also dedicated to him.

Asteroid 294727 Dennisritchie, discovered by astronomers Tom Glinos and David H. Levy in 2008, was named in his honor. The official naming was announced by the Minor Planet Center on February 7, 2012, in Minor Planet Circulars (M.P.C.) 78272.

Notable works

• The B programming language
• The C programming language, which many other programming languages and technologies are based on
• Unix, a multiuser operating system. Many similar systems, called Unix-like systems, were created using Unix's design. Some of these systems follow POSIX standards, which are also based on Unix
• The Unix Programmer's Manual (1971)
• The C Programming Language (also known as K&R), written in 1978 by Brian Kernighan and others

Publications and academic papers

Ritchie has written or helped write about 50 academic papers, books, and textbooks. These works have been cited more than 15,000 times.

Some of his most frequently cited works include:

• The C Programming Language, by BW Kernighan and DM Ritchie, published by Prentice Hall (1978)
• Programming Languages, by D Ritchie (1978)
• The UNIX Time-Sharing System, by DM Ritchie and K Thompson, in Classic Operating Systems (2001)
• Advanced Programming in the Unix Environment, by WR Stevens, SA Rago, and DM Ritchie, published by Addison-Wesley (1992, 2008)