1. Introduction to maintainability

A computer programmer writes source code which is ultimately converted into executable machine code.

Once the machine code has been created and stored in a file, you could in theory just throw away the source code. After all, the program will run perfectly well without it.

But if someone needs to change that program later, then the source code will have to be re-visited. So it is usually a bad idea to discard the original source code.

A program may need modifying for any of the following reasons:

• To add a new feature
• To fix a bug
• To improve the speed or performance
• To port it so that it will run on a different CPU or Operating System

The process of ensuring that code can be easily amended or updated is called Maintainablility.

There are several standard techniques to help with maintainability that every programmer should follow, regardless of which programming language they use to write their code.

We will discuss these techniques in the following few pages, using a worked example to demonstrate.