abs

    #include <stdlib.h>
    int abs(int i);

computes the absolute value of the integer i

#include <stdio.h> /* including standard library */
//#include <windows.h> /* uncomment this for Windows */
 /* for printf */
#include <stdlib.h>
 
int main( void )
{
  int i = -42;
  printf("abs from i = %d\n", abs(i));
  return 0;
}

  user@host:~/code-reference.com# ./abs 
  abs from i = 42