A common mistake people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.

If you're not failing every now and again, it's a sign you're not doing anything very innovative.

On two occasions, I have been asked [by members of Parliament], "Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?" I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question.

All models are wrong; some models are useful.

Good judgment comes from experience; experience comes from bad judgment.

Plan to throw one away; you will anyhow.

Scientists build to learn; Engineers learn to build.

...and then it occurred to me that a computer is a stupid machine with the ability to do incredibly smart things, while computer programmers are smart people with the ability to do incredibly stupid things. They are, in short, a perfect match.

The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the development time.

The sooner you start to code, the longer the program will take.

Any sufficiently advanced technology is indistinguishable from magic.

We don't have time to stop for gas, we're already late.

Whenever there is a hard job to be done I assign it to a lazy man; he is sure to find an easy way of doing it.

Doing more things faster is no substitute for doing the right things.

The generation of random numbers is too important to be left to chance.

Computer Science is no more about computers than astronomy is about telescopes.

If we wish to count lines of code, we should not regard them as lines produced but as lines spent.

Testing can show the presence of errors, but not their absence.

Everything should be made as simple as possible, but not simpler.

Imagination is more important than knowledge.

The biggest difference between time and space is that you can't reuse time.

Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.

The speed of a non-working program is irrelevant.

It's [programming] the only job I can think of where I get to be both an engineer and an artist. There's an incredible, rigorous, technical element to it, which I like because you have to do very precise thinking. On the other hand, it has a wildly creative side where the boundaries of imagination are the only real limitation.

It always takes longer than you expect, even when you take into account Hofstadter's Law.

A ship in port is safe, but that is not what ships are built for. I want all the youngsters to sail out to sea and be good ships.

It's easier to ask forgiveness than it is permission.

Computer Science is the only discipline in which we view adding a new wing to a building as being maintenance.

In the practical use of our intellect, forgetting is as important as remembering.

Should array indices start at 0 or 1? My compromise of 0.5 was rejected without, I thought, proper consideration.

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.

A distributed system is one in which the failure of a computer you didn't even know existed can render your own computer unusable.

The only way for errors to occur in a program is by being put there by the author. No other mechanisms are known. Programs can't acquire bugs by sitting around with other buggy programs.

He who hasn't hacked assembly langauge as a youth has no heart. He who does so as an adult has no brain.

I have made this letter longer than usual, only because I have not had the time to make it shorter.

The purpose of brakes on a car is to allow you to go fast.

The best way to get a good idea is to get a lot of ideas.

Any noun can be verbed.

Fancy algorithms are slow when N is small, and N is usually small.

Computers in the future may weigh no more than 1.5 tons.

If the code and the comments disagree, then both are probably wrong.

Without requirements or design, programming is the art of adding bugs to an empty text file.

Giving the Linus Torvalds Award to the Free Software Foundation is a bit like giving the Han Solo Award to the Rebel Alliance.

I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone.

There are only two kinds of programming languages: those people always bitch about and those nobody uses.

Omit needless words. Vigorous writing is concise. A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts.

There are only two industries that refer to their customers as "users."

It is better to have an approximate answer to the right question than an exact answer to the wrong one.

The problem with using C++... is that there's already a strong tendancy in the language to require you to know everything before you can do anything.

I think there is a world market for maybe five computers.

Software gets slower faster than hardware gets faster.

Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.

Time is an excellent teacher; but eventually it kills all its students.

Weeks of programming can save you hours of planning.

The person who says it cannot be done should not interrupt the person doing it.

It doesn't work to leap a 20 foot casym in 2 10 foot jumps.

No matter how far you have gone on the wrong road, turn back.