Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!maytag!watstat!dmurdoch
From: dmurdoch@watstat.waterloo.edu (Duncan Murdoch)
Newsgroups: comp.lang.pascal
Subject: Re: Problem in Turbo Pascal 4.0
Keywords: Nonterminating Repeat loop, real, representation, binary coded decimal
Message-ID: <1080@maytag.waterloo.edu>
Date: 4 Jan 90 00:42:36 GMT
References: <4658@ur-cc.UUCP> <4660@ur-cc.UUCP> <803@tuewsd.lso.win.tue.nl> <4679@ur-cc.UUCP>
Sender: daemon@maytag.waterloo.edu
Reply-To: dmurdoch@watstat.waterloo.edu (Duncan Murdoch)
Organization: U. of Waterloo, Ontario
Lines: 21

In article <4679@ur-cc.UUCP> lowj_ltd@uhura.cc.rochester.edu (John Alan Low, aka "Travis" Low) writes:
>     After I read this, I compiled the program with the Turbo Pascal 3.0
>     turbobcd.com compiler. Guess what? The loop terminates nicely. Also,
>     expressions such as 1/3 + 2/3 come out equal to 1.0. So the binary-
>     coded representation of decimals works nicely, and the "=" works the
>     way it's supposed to.

It's not surprising that the original sum of 0.01's came out exact, because
they can be represented exactly in BCD.  I think you were just lucky with 
the other one - you probably added 0.3...33 + 0.6...67 and got 1.  You might
try it again adding 3 copies of 1/3, and should get 0.999...
>
>     Is there some reason this representation is not common practice? 
>     Can anybody shed some light on this? I think that later versions of
>     Turbo Pascal do not implement this representation, so there must be
>     some good reason, right? 

You're right about recent (4.0+) versions of TP.  You can get them in
the Turbo Professional library from Turbopower, if you want.  

Duncan Murdoch