Edsger Dijkstra's note on starting array indices at 0 (pdf, 1982)
Humans don't start counting at zero, though―we start counting at one. Zero, in fact, was a concept introduced to our arithmetic much later.<p>A list of twenty items <i>has</i> a twentieth item.<p>Dijkstra is far too mathematical with this―no student learning programming for the first time (<i>edited</i>: changed from programmer) <i>in the world</i> ever thought "arrays starting at 0―how natural!".