Semaphores notation - why V and P instead of S and W

Question

I am asking this question because I'm trying to get the notation to stick in my head. My lecturer said that V and P are the first letters of the dutch words for signal and wait, but this is not true.

Does anyone know what words V and P abbreviate or did Dijkstra just pick his favorite two letters?

Answer 1

From Wikipedia's Semaphore (programming) article and a copy of Dijkstra's work:

• Probeer te verlagen (P) means 'try to decrement'
• Verhogen (V) means 'increment'

P has the Proberen... (try) term in front of the meaningful verlagen (decrement) term because the Dutch words for increment and decrement both start with "V". Dijkstra added the "try to" words in front of the meaningful "decrement" term so that there would be a simpler way of distinguishing between the two functions.