#include <stdio.h>
main()
{
int i,j,k;
i = 2;
j = 10;
k = i++ - i++;
printf("i=%d, j = %d, k = %d\n",i,j,k);

i = 2;
j = 10;
k = ++i - ++i;
printf("i=%d, j = %d, k = %d\n",i,j,k);

i = 2;
j = 10;
k = i++ + i++;
printf("i=%d, j = %d, k = %d\n",i,j,k);

i = 2;
j = 10;
k = ++i + ++i;
printf("i=%d, j = %d, k = %d\n",i,j,k);
}

which outputs:
k = 0
k = 0
k = 4
k = 8