In the context of computer science, code can have two meanings. First, code is a set of symbols designed to represent an object or expression. A common example is the ASCII codes used to depict characters. Code is also written computer instruction--sequences of information that convey function.

Code as computer instruction can appear in a variety of forms. The code that a computer programmer writes is called source code. This type of code is written in whatever programming language is in use with the computing system. Source code must be converted into a language that the computer can understand--machine language--before it can be usefully implemented. The translation is accomplished by a utility called a compiler.

Source code is the only arrangement of code that is readable by humans. The source code is often supplied by a vendor in a form that cannot be read or modified by the...