Donald E. Knuth

The designer of a new kind of system must participate fully in the implementation.

... the designer of a new system must not only be the implementor and the first large-scale user; the designer should also write the first user manual. ... If I had not participated fully in all these activities, literally hundreds of improvements would never have been made, because I would never have thought of them or perceived why they were important.

Beware of bugs in the above code; I have only proved it correct, not tried it.

I get into the meanest, nastiest frame of mind I can manage, and I write the nastiest (testing) code I can think of. Then I turn around and embed that in even nastier constructions that are nearly obscene.

Let us change our traditional attitude to the construction of programs. Instead of imagining that our main task is to instruct a computer what to to, let us concentrate rather on explaining to human beings what we want a computer to do.

You're bound to be unhappy if you optimize everything.

The process of preparing programs for a digital computer is especially attractive, not only because it can be economically and scientifically rewarding, but also because it can be an aesthetic experience much like composing poetry or music.

Any inaccuracies in this index may be explained by the fact that it has been sorted with the help of a computer.

Computers are good at following instructions, but not at reading your mind.

When I speak about computer programming as an art, I am thinking primarily of it as an art form, in an aesthetic sense. The chief goal of my work as an educator and author is to help people learn how to write beautiful programs...My feeling is that when we prepare a program, the experience can be just like composing poetry or music...Some programs are elegant, some are exquisite, some are sparkling. My claim is that it is possible to write grand programs, noble programs, truly magnificent ones!... computer programming is an art, because it applies accumulated knowledge to the world, because it requires skill and ingenuity, and especially because it produces objects of beauty. Programmers who subconsciously view themselves as artists will enjoy what they do and will do it better.

We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil.

The most effective debugging techniques seem to be those which are designed and built into the program itself.

Debugging is an art that needs much further study. The most effective debugging techniques seem to be those which are designed and built in to the program itself. Another good debugging practice is to keep a record of every mistake that is made. Even though this will probably be quite embarrassing, such information is invaluable to anyone doing research on the debugging problem, and it will also help you learn how to reduce the number of future errors.

I am pleased to see that TeX actually kept getting simpler as it kept growing, because the new features blended with the old ones. I was constantly bombarded by ideas for extensions, and I was constantly turning a deaf ear to everything that did not fit well with TeX as I conceived it at the time. Thus TeX converged, rather than diverged, to its final form. By acting as an extremely conservative filter, and by believing that the system was always complete, I was perhaps able to save TeX from the 'creeping featurism' that destroys systems whose users are allowed to introduce a patchwork of loosely connected ideas.

The psychological profile [of a programmer] is mostly the ability to shift levels of abstraction, from low level to high level. To see something in the small and to see something in the large. When you're writing a program, you're saying, "Add one to the counter," but you know why you're adding one to the counter. You can step back and see a picture of the way a process is moving. Computer scientists see things simultaneously at the low level and the high level.

The first thing I would say is that when you write a program, think of it primarily as a work of literature. You're trying to write something that human beings are going to read. Don't think of it primarily as something a computer is going to follow. The more effective you are at making your program readable, the more effective it's going to be: You'll understand it today, you'll understand it next week, and your successors who are going to maintain and modify it will understand it.

...in fact what I would like to see is thousands of computer scientists let loose to do whatever they want. That's what really advances the field.

Any inaccuracies in this index may be explained by the fact that it has been sorted with the help of a computer.

The most important thing in the programming language is the name. A language will not succeed without a good name. I have recently invented a very good name and now I am looking for a suitable language.

When using WYSIWYG systems, What You See Is All You'll Ever Get.

Premature optimization is the root of all evil.

I believe that the final bug in TeX was discovered and removed on November 27, 1985. But if, somehow, an error still lurks in the code, I shall gladly pay a finder's fee of $20.48 to the first person who discovers it. (This is twice the previous amount, and I plan to double it again in a year; you see, I really am confident!)

The hardest thing is to go to sleep at night, when there are so many urgent things needing to be done. A huge gap exists between what we know is possible with today's machines and what we have so far been able to finish.

You're bound to be unhappy if you optimize everything.

The best programs are written so that computing machines can perform them quickly and so that human beings can understand them clearly.