Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!decwrl!sun!pitstop!sundc!seismo!uunet!mcvax!hp4nl!philapd!wc8!lexw
From: lexw@idca.tds.PHILIPS.nl (Lex Wassenberg)
Newsgroups: comp.arch
Subject: Re: foreign language requirements for PhDs
Summary: explanation for Dijkstra's P and V operators
Keywords: Dijkstra, P, V, operators
Message-ID: <210@wc8.idca.tds.philips.nl>
Date: 13 Mar 89 08:53:26 GMT
References: <7287@spool.cs.wisc.edu> <2851@eos.UUCP> <401@rb-dc1.UUCP> <21572@shemp.CS.UCLA.EDU> <1280@wpi.wpi.edu> <134@cs.columbia.edu>
Organization: Philips Telecommunication and Data Systems, The Netherlands
Lines: 56

In article <134@cs.columbia.edu> kan@cs.columbia.edu (Victor Kan) writes:
>
>Consider this hypothetical example:
>-----
>Let's say Dijkstra's 1965 "Co-operating Sequential Processes"
>work was written in Dutch.  The translators at Academic Press in
>London translate it into English, retaining P and V as the
>semaphore operations.  CS PhD students in the U.S.  read this
>translation, get confused and wonder "What the hell do P and V
>mean with respect to mutual exclusion?"  If the students had no
>experience with foreign languages, they would might beat
>themselves over the head trying to figure it out.  Then some wise
>guy who knows Dutch says P is short for wait and V is short for
>signal in Dutch.  BOOM! it's perfectly clear to everyone that P
>means if I can't have access, then I'll wait in the queue, while
>V means signal the next process in the queue that I'm done.
>-----

Well Victor, although I will not claim that I'm a wise guy, I *am* Dutch
and I can say to you that P is *not* short Dutch for wait, and that V is
*not* short Dutch for signal. However, during a course I followed last year
I heard a completely different explanation of how Dijkstra came to his
P and V operators. I don't know whether it's correct or not, but here it is:

During the time that Dijkstra wrote the paper mentioned above, he was working
in Eindhoven, the home town of the Philips company (maybe he was even working
for Philips?). He was thinking about suitable names for the "wait" and "signal"
operators but couldn't think of any good names. His room was at the top of a
flat next to the soccer stadium of Eindhoven. When he looked out of the window,
he saw the stadium with on top of it in big letters the name of the club that
had it their home stadium. The name of the club was PSV (Philips Sport 
Vereniging, Dutch for Philips Sport Union. Maybe you know the name, it's the
club that won the Europe Cup last year, and is playing next wednesday against
Real Madrid for the same cup of this year). Since Dijkstra had his semaphore
already given the name "S", he decided that the P and the V would make a nice
triplet together with the S.

As I said, I don't know whether it's true or not. Apparantly, Dijkstra himself
is the only one who can say anything about this topic with authority. But during
the course, we discussed it several times (we were with 16 Dutch guys) and
nobody could give any satisfying explanation for the P and V abbreviations, so
we decided that that the story might be true.


P.S. [no V.  :-)  ] I know comp.arch is not really suited for this story,
     but where else should I post it, as the article I was reacting to was
     also posted here?


      ________________
     /  /  ___  _____/      Lex Wassenberg, Philips TDS
    /  /  /__ \/ ___/       Apeldoorn, The Netherlands
   /  /  ___/   /__         lexw@idca.tds.philips.nl
  /  /  /____/\___/                                            
 /  /____________/ It's said that only 10 people on the whole world understood
/_______________/  Einstein. I'm so brilliant that no-one understands me at all.