Introduction — What is a compiler?

Abstract

A computer programmer who writes a new program chooses one of the many programming languages available. The language is not directly understandable by his computer system so some software is needed to bridge the gap between language and computer. This software is a compiler. There is nothing magical or special about a compiler. Compiling is just a particular data processing task in which the input or data is the source text, a program written in a language like Pascal, and the output is an equivalent program, known as the object code program, suitable for running on some computer. One form of object program is a set of binary instructions for a particular computer such as the PDP11 or Motorola 68000. Even binary instructions can be regarded as a primitive language, so a compiler is in fact a simple example of a translator. Translators are a class of objects which accept input in one language and generate an equivalent output in another language. This translation could be done by hand, with pencil and paper, but it would be an incredibly tedious and error-prone task. Fortunately the translation task for computer languages is sufficiently straightforward that it can best be handled by a computer.