<P> In 1972 , Unix was rewritten in the C programming language . The migration from assembly 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 . Bell Labs produced several versions of Unix that are collectively referred to as Research Unix . In 1975 , the first source license for UNIX was sold to Donald B. Gillies at the University of Illinois Department of Computer Science . UIUC graduate student Greg Chesson ( who had worked on the UNIX kernel at Bell Labs ) was instrumental in negotiating the terms of this license . </P>
<P> In 1972 , Unix was rewritten in the C programming language . The migration from assembly 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 . Bell Labs produced several versions of Unix that are collectively referred to as Research Unix . In 1975 , the first source license for UNIX was sold to Donald B. Gillies at the University of Illinois Department of Computer Science . UIUC graduate student Greg Chesson ( who had worked on the UNIX kernel at Bell Labs ) was instrumental in negotiating the terms of this license . </P>
the first unix operating system was written in which language
the first unix operating system was written in which language
assembly
assembly