A Brief History of C Programming Language ๐Ÿ“œ

A Brief History of C Programming Language ๐Ÿ“œ

Since 1972


8 min read

C is a pretty old language. C is a byproduct of the UNIX project. UNIX led to the development of C and C helped UNIX to gain further success.

70s ๐Ÿ•บ

The history of the C programming language dates back to 1969. Ken Thompson started to develop a language called B (a kind of stripped-down version of BCPL) around 1969 [1]. In 1971, Dennis Ritchie started to improve the B language and called this new language New B or NB, in short. After several modifications to B, he decided to give a distinct name to this modified B language and created the C language in 1972.

Ken Thompson (sitting) and Dennis Ritchie at PDP-11. Origin

But why the name C? It is believed that Ritchie selected the letter C (the next letter after B in the English alphabet) because the language was derived from the B programming language [2]. Another less common theory is as follows. We know that B had derived from BCPL. Ritchie chose the name C because the letter after B is C in BCPL. If there was a third language after C, that would be P language, not D. We are not sure about the reason because as far as I know, Ritchie didn't explain the rationale behind selecting this name. By the way, there is a D programming language, but it is not considered a successor of C. The language derived from C is C++.

6 years after the birth of C, in 1978, Brian Kernighan and Ritchie published The C Programming Language book. This book is very well known and still very famous today. It is the bible of C. The version of C explained in that book is known as K&R C (notice that K and R are the initials of the surnames of the authors). At that time, the C language was not yet standardized as it is today. This book is considered the standard for the language that was not standardized formally in 1978. The C version described in this book can also be called C78, although it is very uncommon.

The C Programming Language, first edition, 1978. Origin

This is one of the first programming books to have the classical Hello World example.

printf("hello, world\n");

The "real" Hello World by Brian Kernighan. Origin

80s ๐ŸŽธ

Around 1983, the first standardization committee was established by ANSI (American National Standards Institute). In 1989, ANSI published the first C standard, known as ANSI C or C89. In 1990, ISO (International Organization for Standardization) adopted the ANSI C standard, did non-technical modifications and published the ISO C or C90 standard. Indeed, all four of them (ANSI C, C89, ISO C and C90) refer to the same standard, and today they are used interchangeably. Until the publication of the first standard in 1989, K&R C (the C explained in the book) was the de facto standard. In 1988, the same authors (K&R) published the second and the last version of The C Programming Language [5]. This edition covers the ANSI C standard. The following standards have only been published by ISO, and ANSI has not published any other standard.

The C version used between the birth of C (around 1970) and the first standard (1989/1990) is also known as classic C or traditional C.

90s ๐Ÿ’พ

Several modifications were made to the rules of the language after the first standard. The second major standard known as C99 was published in 1999. Before C99, C95 was published in 1995, but there are no significant differences between C95 and C90. However, the differences between C90 (ANSI C, ISO C or C89, whatever you choose) and C99 are significant.

Today, most of the programmers talk about C99 when they say C. I observe that C99 is the dominant version, especially in the embedded world. Yes, it is quite old, but this is the case.

C++ and C

The first C++ standard was published in 1998 as C++98. Today, the C that exists in C++ differs from the C language itself. The C++ developers created a modified C within the C++ language. The C supported in C++ isn't the same as the C programming language. They fixed some ambiguous rules and added new features to C90 while preparing C++98. Since they were creating a new language, they had no concerns (almost) like backward compatibility, and they were free to do whatever they wanted. Some suitable features and corrections done by C++ developers are backported to the C language with C99, so to speak.

2000s ๐Ÿ“ฑ

In 2011, the third major standard, C11, was published. Some new features like multi-threading are added to the language with this version.

In 2018, C17 (also known as C18) was published. C17 didn't introduce new features to the language and only did some technical corrections and clarifications to specifications in C11.

The next version after C17 is C23. The new version is expected to be published in 2024 as C23 [3, 4, 7].

Standards ๐Ÿ“

The standards can be summarized as follows. Please keep in mind that the C language was born in 1972.

YearInformal Name(s)Formal Standard Name(s)
1970sclassic C, traditional C-
1978K&R C, C78-
1989/1990ANSI C, ISO C, C89, C90ISO/IEC 9899:1990, ANSI X3.159-1989(?)
1995C95ISO/IEC 9899:1990/AMD1:1995
1999C99ISO/IEC 9899:1999
2011C11ISO/IEC 9899:2011
2018C17, C18ISO/IEC 9899:2018
2024C23ISO/IEC 9899:2024

At that moment, C23 is expected to be finalized in 2024.

UNIX and C

At the beginning, I said that C is a byproduct of the UNIX project. Now, let's look at the history of UNIX briefly.

In 1964, MIT started a new project. The main aim of this project was to create a time-sharing operating system to allow multiple users to use expensive computers. This is the famous Multics ("MULTiplexed Information and Computing Service") operating system project. There were 3 big players in the project: MIT, General Electric and Bell Labs. One of the participants from Bell Labs was Ken Thompson. After some time and for some (probably economical) reason, Bell Labs withdrew from the project and decided to design their operating system. The name of this project is UNIX, well actually "Unics" (UNiplexed Information and Computing System) [8]. The word Unix is sort of a word joke, M in Multics stands for "Multiplexed" and U stands for "Uniplexed" although both of them target multi-user usage [6].

In 1969 (the same year that Linus Torvalds was born), Thompson and his colleagues started to work on DEC PDP-7 and they implemented the UNIX. In 1970, UNIX was rewritten for DEC PDP-11, again in assembly. First, they started to write UNIX in assembly language and then they thought that getting help from a higher-level language could be a good idea. In those days, BCPL was a popular system programming language. BCPL had been derived from CPL and CPL is a successor of Algol. While working with BCPL, Ken Thompson created a B language and then Dennis Ritchie continued to work on B and created the C language. So, we can say that Algol is the ancestor of C. Even though they got help from higher languages, the team was still writing UNIX in assembly. Notice that the UNIX project is older than the C language.

After a couple of years, C was mature enough and they decided to rewrite the whole project in C. This is the first biggest success of the C programming language. In 1973, UNIX (Version 4) was rewritten in C. Today, most of us would say that C is a low-level language like assembly because we know higher-level languages like Python and C#. But back in those days, writing an operating system in a high-level language like C was revolutionary. Before C the main language of operating systems was assembly. Can you feel the pain? Porting an assembly program to another architecture is PITA. But once you write a program in C and if you have a compiler for the target architecture, then you can easily port the program. UNIX is not an exception, it had a little architecture-dependent assembly code, but most of the code was in portable C.

In 1978, K&R published The C Programming Language book. Besides being the first book on the C language, it also covered UNIX and UNIX programming.

In programming languages word, it is common that a language is influenced by its predecessors and this is true for C.

In summary:

Personal Computers and C ๐Ÿ’ป

The personal computer revolution had begun in the early 1980s. For example, IBM released their famous Personal Computer (PC) in those years. Nowadays, the C language is mainly used in the embedded world, operating systems and system programming. But with the personal computer revolution, C was preferred for almost all kinds of programs. C became a great choice not only for operating system programmers but for all programmers.

Related ๐Ÿ”—

Brian Kernighan (K of K&R) talking about The C Programming Language book and a bit of history.

Brian Kernighan on Computerphile Channel:

You can also check out this interview: Brian Kernighan and Lex Fridman.