A third theme is to show how common computing operations are done. In each case, a short awk program conveys the essence of how something works in a form that you can understand and play with. We have also tried to illustrate a spectrum of ways to attack programming problems. Rapid prototyping is an approach that awk supports well. Another is writing programs that create other programs.
Little languages define a good user interface and often suggest a sound implementation.
Although these ideas are presented here in the context of awk, they are much more generally applicable and ought to part of every programmer's repertoire. The examples have all been tested directly from the text, which is in machine-readable form. We have tried to make the programs error-free, but we have not added features nor made them proof against all possible invalid inputs, preferring to concentrate on conveying the essentials. Evolution of the AWK language Awk was originally designed and implemented by the authors in 1977, in part as an experiment to see how the Unix gools grep and sed could be generalized to deal with numbers as well as text. It was based on our interests in regular expressions and programmable editors.