It is easier to change the specification to fit the program than vice versa.
Programmers are not to be measured by their ingenuity and their logic but by the completeness of their case analysis.
In software systems it is often the early bird that makes the worm.
Every program has (at least) two purposes: the one for which it was written and another for which it wasn't.
To understand a program, you must become both the machine and the program.
One can only display complex information in the mind. Like seeing, movement or flow or alteration of view is more important than the static picture, no matter how lovely.