Unix is primarily written in the C language, with some small snippets of assembler code for low level bootstraps.
C and assembly
UNIX was programmed in C.
The Unix operating system. The first versions of the Unix operating system were written in the "B" language, and later written in "C", which was invented in order to develop Unix on the PDP-11 machine.
C. Schirmer has written: 'Programming in C for UNIX' -- subject(s): C (Computer program language), UNIX (Computer file)
Unix was created first. The C programming language was created for Unix.
The C programming language was originally created for Unix. Unix, and most other Unix-like systems such as Linux, are written almost entirely in C.
Terrence Chan has written: 'UNIX system programming using C++' -- subject(s): C++ (Computer program language), C
C/C++ is used to write system softwares. The whole of UNIX operating system is written in C language.
The AWK programming language is a Unix based programming language, and is sometimes considered as a pseudo-C interpreter. It is mainly used for sifting through and organizing large amounts of data at one time.
Unix was rewritten in the C Programming language and not in assembly language. The migration from assembly language to the higher-level language C resulted in much more portable software, requiring only a relatively small amount of machine-dependent code to be replaced when porting Unix to other computing platforms. (mihir)
PHP is written in the C programming language.
KSH is an abbreviation for korn shell. Korn shell is a command interpreter for the Unix programming language. It was written in 1983 by David Korn at Bell Labs.
Advanced Programming in the Unix Environment was created in 1992.