plus.c

#include <stdio.h>

/* Bitwise integer addition */
int plus(int x, int y)
{
    int result = x ^ y;
    int carry = (x & y) << 1;

    if (carry != 0)
        return plus(result, carry);

    return result;
}

int main(int argc, char **argv)
{
    printf("%d\n", plus(3, 4));
    printf("%d\n", plus(5, 6));
    printf("%d\n", plus(5, 10));
    printf("%d\n", plus(35, 100));
    printf("%d\n", plus(-8, 2));
    printf("%d\n", plus(93, -208));
    printf("%d\n", plus(-93, -208));
}