C Tutorial/time.h/difftime
difftime
Item Value Header file time.h Declaration double difftime(time_t time2, time_t time1); Return returns the difference, in seconds, between time1 and time2( time2 - time1).
#include <time.h>
#include <stdio.h>
int main(void)
{
time_t start, end;
volatile long unsigned t;
start = time(NULL);
for(t=0; t<500; t++) ;
end = time(NULL);
printf("Loop used %f seconds.\n", difftime(end, start));
return 0;
}