An effective way to test code is to exercise it at its natural boundaries

Some compilers allow a check during execution that subscripts do not exceed array dimensions. This is a help, but not sufficient. First, many programmers do not use such compilers because They're not efficient. (Presumably, this means that it is vital to get the wrong answers quickly.)

Each new user of a new system uncovers a new class of bugs.

Do what you think is interesting, do something that you think is fun and worthwhile, because otherwise you won't do it well anyway.

As we said in the preface to the first edition, C "wears well as one's experience with it grows." With a decade more experience, we still feel that way.

Controlling complexity is the essence of computer programming.

Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it.