I write an average of five new programs every week. Poets have to write poems. I have to write computer programs.

The ultimate test of whether I understand something is if I can explain it to a computer. I can say something to you and you’ll nod your head, but I’m not sure that I explained it well. But the computer doesn’t nod its head. It repeats back exactly what I tell it. In most of life, you can bluff, but not with computers.

Donald Knuth in Quanta Magazine: The Computer Scientist Who Can’t Stop Telling Stories