# 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.
## See also

**ctime**(S),
**mktime**(S),
**nl_cxtime**(S),
**stime**(S),
**time**(S)
## 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.

This program calculates the amount of time needed to find the prime
numbers between 3 and 10,000. To display the prime numbers, delete
the outermost loop and the comment delimiters around the expression
`printf("%d",n);`

.

*
© 2003 Caldera International, Inc. All rights reserved.
*

SCO OpenServer Release 5.0.7 -- 11 February 2003