difftime(S)

difftime -- computes the difference between time values

Syntax

cc . . . -lc

#include <time.h>

double difftime(time2, time1)
time_t time2;
time_t time1;

Description

The difftime function computes the difference of time2

time1.

See the example which follows.

Return value

The difftime function returns the elapsed time in seconds from time1 to time2 as a double-precision number.

Standards conformance

difftime is conformant with:

ANSI X3.159-1989 Programming Language -- C .

Example

   #include <time.h>
   
   int mark[10000];
   

   main()
   {
           time_t  start, finish;
           register int i, loop, n, num, step;
           printf("This program takes about 3 minutes ");
           printf("on an AT and 8 on a PC.\n Working...\n");
           time(&start);
   

           for (loop = 0; loop < 1000; ++loop)
              for (num = 0,n = 3; n < 10000; n += 2)
                   if (!mark[n])
                      {
                      /* printf("%d\n",n); */
                      step = 2*n;
                      for (i = 3*n; i < 10000; i += step)
                        mark[i] = -1;
                      ++num;
                      }
           time(&finish);
   

           /* Prints average of 1000 loops through "sieve": */
           printf("\nProgram takes %f seconds to find %d primes.\n",
           difftime(finish, start), num);
   }

Output:

   Program takes 0.482000 seconds to find 1228 primes.