The first unix operating system was written in which language?
The operating system was originally written in assembly language, 
The first unix operating system was originally written in which language?
Assembly
Unix
No context provided
The first unix operating system was rewritten in which language?
C
Unix
https://en.wikipedia.org/wiki/Unix
History of Unix
https://en.wikipedia.org/wiki/History%20of%20Unix
Unix (/ˈjuːnɪks/; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in the 1970s at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others.
Unix
In 1973, Version 4 Unix was rewritten in the higher-level language C, contrary to the general notion at the time that an operating system's complexity and sophistication required it to be written in assembly language.
History of Unix 1970s
Unix is a family of multitasking, multiuser computer operating systems whose development started in the 1970s at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others. The operating system was originally written in assembly language, but in 1973, Version 4 Unix was rewritten in the higher-level language C, contrary to the general notion at the time that an operating system's complexity and sophistication required it to be written in assembly language.