The 'C' programming language was designed and developed by Brian Kernighan, and Dennis Ritchie at The Bell Research Labs. 'C' is a Language specificallycreated in order to allow the programmer access to almost all of the machine's internals - registers, I/O slots and absolute addresses. However, at the same time,'C' allows for as much data hiding and programme text modularization as is needed to allow very complex multi-programmer projects to be constructed in an organized and timely fashion. During the early 1960s computer Operating Systems started to become very much more complex with the introduction of multi-terminal and multi-process capabilities.

Prior to this time Operating Systems had been carefully and laboriously crafted using assembler codes, and many programming teams realized that in order to have a working o/s in anything like a reasonable time this was now longer economically feasible. This then was the motivation to produce the 'C' Language, which was first implemented in assembler on a Digital Equipment Corporation PDP-7. Of course once a simple assembler version was working it was possible to rewrite the compiler in 'C' itself. This was done in short order and therefore as soon as the PDP-11 was introduced by DEC it was only necessary to change the code generator section of the compiler and the new machine had a compiler in just a few weeks. 'C' was then used to implement the UNIX o/s. 

This means, that a complete UNIX can be transported, or to use the simple jargon of today; 'ported to a new machine in literally just a few months by a small team of competent programmers. Enough of the past. Lets see the various actions, or compilation phases through which the `C' compilation system has to go in order that your file of `C' program text can be converted working program.