Evo ti primer iz msdn-a:
Za abs() ti treba stdlib.h ili math.h a za __abs64() stdlib.h.
Code:
/* ABS.C: This program computes and displays
* the absolute values of several numbers.
*/
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
void main( void )
{
int ix = -4, iy;
long lx = -41567L, ly;
double dx = -3.141593, dy;
__int64 wx = -1, wy;
wy = _abs64( wx );
printf( "The absolute value of %I64x is %I64x\n", wx, wy);
iy = abs( ix );
printf( "The absolute value of %d is %d\n", ix, iy);
ly = labs( lx );
printf( "The absolute value of %ld is %ld\n", lx, ly);
dy = fabs( dx );
printf( "The absolute value of %f is %f\n", dx, dy );
}