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From: dik@uva.UUCP (Casper H.S. Dik)
Newsgroups: comp.unix.wizards,comp.lang.c
Subject: Re: Problem with printf()
Message-ID: <548@uva.UUCP>
Date: 6 Oct 88 14:00:28 GMT
References: <504@imec.UUCP>
Sender: news@uva.UUCP
Reply-To: dik@uva.UUCP (Casper H.S. Dik)
Organization: Faculteit Wiskunde & Informatica, Universiteit van Amsterdam
Lines: 41

In article <504@imec.UUCP> croes@imec.UUCP (Kris Croes) writes:
>Hello NetLand, 
>
>May I introduce to you...
>A little program containing a big problem.
>  main()
>  {
>  int i = 17;
>  float f = 17.0;
>
>  printf("%d %f\n",i,i); /*1*/
>  printf("%d %f\n",f,f); /*2*/
>  }
>
>Its output is:
>17 0.000000
>17032 0.000000
>      ^^^^^^^^ Shouldn't this be 17.00000 ?
>
No wonder, float arguments in C are converted to doubles before being passed
to functions. So printf expects sizeof(int)+sizeof(double) bytes but gets
sizeof(double)+sizeof(double). Since sizeof(double) > sizeof(float) this
results in printf interpreting garbage as data, thus resulting in
GIGO (Garbage In, Gospel Out).

If you had read the entire printf manual, you would have been put on the
right track by the explanation of %f '... converts the float or double 
argument ...'.

BTW you posted to the wrong news group. Printf is a standard C function
and the proper newsgroup would be comp.lang.c.

____________________________________________________________________________
Casper H.S. Dik
Student
University of Amsterdam     |		      dik@uva.uucp
The Netherlands             |                 ...!uunet!mcvax!uva!dik
____________________________________________________________________________
Casper H.S. Dik
University of Amsterdam     |		      dik@uva.uucp
The Netherlands             |                 ...!uunet!mcvax!uva!dik