Return-Path: Delivery-Date: Received: from leopard.cs.byu.edu (no rfc931) by swan.cl.cam.ac.uk with SMTP (PP-6.5) outside ac.uk; Wed, 17 May 1995 11:40:05 +0100 Received: by leopard.cs.byu.edu (1.37.109.15/16.2) id AA235745635; Wed, 17 May 1995 04:13:55 -0600 Sender: info-hol-request@lal.cs.byu.edu Errors-To: info-hol-request@lal.cs.byu.edu Precedence: list Received: from daisy (daisy.inmos.co.uk) by leopard.cs.byu.edu with ESMTP (1.37.109.15/16.2) id AA235445596; Wed, 17 May 1995 04:13:16 -0600 From: shepherd_david/uk_bristo_br@brx001.bristol.st.com Received: by daisy id LAA07987; Wed, 17 May 1995 11:13:20 +0100 Received: from by brx001 with SMTP (1.37.109.11/16.2) id AA232244597; Wed, 17 May 1995 10:56:37 +0100 X-Openmail-Hops: 1 Date: Wed, 17 May 95 10:54:25 +0100 Message-Id: In-Reply-To: <9505162347.AA04588@oahu.cs.ucla.edu> Subject: Question on Dijkstra Quote To: homeier@cs.ucla.edu Cc: info-hol@leopard.cs.byu.edu Item Subject: Message text > Some time ago I heard that E. W. Dijkstra had once said or written > something to the following effect: > > "Testing is fine for showing the presence of errors; > but it is useless for showing their absence." > > Try as I might, I have not been able to pin down the source of > this quote. Can anyone refer me to an article, book, etc. that I can > reliably quote? Also, what was the actual, literal quote? > > It seems like such a standard part of the folklore that I thought > it would be easy to find, but it hasn't been quickly obvious from the > books I have here. I think I once used this in something I wrote, however the only reference to it I could find was that Tony Hoare quoted it (without reference!) in one of his papers. ----------------------------------------------------------------------- david shepherd SGS-THOMSON Microelectronics Ltd, 1000 aztec west, bristol bs12 4sq, UK tel/fax: +44 1454 611638/617910 email: des@bristol.st.com www: http://www.inmos.co.uk/~des/welcome.html "whatever you don't want, you don't want negative advertising"