Rushing to optimize before the bottlenecks are known may be the only error to have ruined more designs than feature creep. From tortured code to incomprehensible data layouts, the results of obsessing about speed or memory or disk usage at the expense of transparency and simplicity are everywhere. They spawn innumerable bugs and cost millions of man-hours - often, just to get marginal gains in the use of some resource much less expensive than debugging time

The only way to write complex software that won't fall on its face is to hold its global complexity down - to build it out of simple pieces connected by well-defined interfaces, so that most problems are local and you can have some hope of fixing or optimizing a part without breaking the whole

Lisp was far more powerful and flexible than any other language of its day; in fact, it is still a better design than most languages of today, twenty-five years later. Lisp freed ITS's hackers to think in unusual and creative ways. It was a major factor in their successes, and remains one of hackerdom's favorite languages.

Prototype, then polish. Get it working before you optimize it

Complexity control is the central problem of writing software in the real world

With enough eyes, all bugs are shallow.

The easiest programs to use are those which demand the least new learning from the user