Testing shows the presence, not the absence of bugs - Edsger W. Dijkstra

For me, the first challenge for computing science is to discover how to maintain order in a finite, but very large, discrete universe that is intricately intertwined. And a second, but not less important challenge is how to mould what you have achieved in solving the first problem, into a teachable discipline: it does not suffice to hone your own intellect (that will join you in your grave), you must teach others how to hone theirs. The more you concentrate on these two challenges, the clearer you will see that they are only two sides of the same coin: teaching yourself is discovering what is teachable.

The problems of the real world are primarily those you are left with when you refuse to apply their effective solutions.

Computer science is not about machines, in
the same way that astronomy is not about
telescopes. There is an essential unity of
mathematics and computer science.