Path: utzoo!mnetor!geac!torsqnt!tmsoft!list-injector
From: steve@cohort.UUCP (Steve Bird)
Newsgroups: can.usrgroup
Subject: C code (fwd)
Message-ID: <9002280838.AA01415@cohort.uucp>
Date: 28 Feb 90 13:38:06 GMT
Reply-To: Steve Bird <steve@cohort.UUCP>
Distribution: ont
Lines: 35
X-Mailer: ELM [version 2.2 PL7]

Forwarded message:

>From steve Fri Nov 24 21:46:23 1989
Subject: C code
To: evan@telly (Evan Leibovitch)
Date: Fri, 24 Nov 89 21:46:23 EST
From: Steve Bird <steve@cohort.UUCP>
X-Mailer: ELM [version 2.2 PL7]

 Here's another interesting piece. 

     /* floaterr.c--demonstrates round-off error */
     # include <stdio.h>
     main()
       {
         float a,b;
         b = 2.0e20 + 1.0;
         a = b - 2.0e20;
         printf("%f \n",a);
       }

  When compiled the program returns the number 4008175468544.000000 .
  Now when the program is modified to read :

     /* floaterr.c--demonstrates round-off error */
     # include <stdio.h>
     main()
       {
         float a,b;
         b = 2.0e20 + 1.0;
         a = 2.0e20;
         printf("%f \n",b - a);
       }

  The program returns 0.000000 . Why ?