Precisely Speaking [Article]
To the scientist and engineer the computer is just a tool, it is an instrucment just like a calculator, a slide-rule, or a micrometer. The computer user must be able to trust the output that the computer gives. Apart from errors which arise from mistakes in the program, there are errors that arise from the computer itself. We have all been told at some time or other that computers do not make mistakes, this is true, but they do have certain inaccuracies which creep into the calculations. It is essential that the programmer is aware of where these inaccuracies may occur and know how to minimise them. The whole topic of errors and the ways in which they may be predicted and minimised is covered in "Numerical Analysis".