Edsger Dijkstra

The sooner we stop thinking in terms of instruction sequences and start thinking in terms of pre- and post-conditions, the better.

The lurking suspicion that something could be simplified is the world's richest source of rewarding challenges.

I don't need to waste my time with a computer just because I am a computer scientist.

In their capacity as a tool, computers will be but a ripple on the surface of our culture. In their capacity as intellectual challenge, they are without precedent in the cultural history of mankind.

It is not the task of the University to offer what society asks for, but to give what society needs.

The problems of the real world are those that remain after you've ignored the ones you've chosen not to solve.

When we had no computers, we had no programming problem either.

The art of programming is the art of organizing complexity, of mastering multitude and avoiding its bastard chaos as effectively as possible.

Our intellectual powers are rather geared to master static relations and... our powers to visualize processes evolving in time are relatively poorly developed.

The ability of the average programmer for conceptualization is very limited, and as a result many programming languages have been specifically designed to cater to this weakness.

I have the feeling that the computing scientist's main challenge is not to get confused by the complexities of his own making.

The belief that there is such a thing as 'the obvious' is a great mistake.

The traditional mathematician recognizes and appreciates mathematical elegance when he sees it. I propose to go one step further, and to consider elegance an essential ingredient of mathematics: if it is clumsy, it is not mathematics.

The moral of this is that we must be very careful when we are told what the problem is: we might accept the problem as posed and, in doing so, implicitly accept premises that are not necessarily justified.

A formula is worth a thousand pictures.

The need for elegance is not a frivolous one. It is a matter of life and death for the program.

The teaching of BASIC should be rated as a criminal offence: it mutilates the mind beyond recovery.

We can found no scientific discipline, nor a hearty profession, on the technical mistakes of the Department of Defense and, mainly, one computer manufacturer.

The vision is that we are to develop programs by a process of gradual refinement, and that we should be able to maintain an overwhelming amount of evidence for their correctness all the time.

The competent programmer is sufficiently aware of the difficulties of the task to be humble about his own abilities.