Add and subtract numbers using bitwise operators :D

bin.c

// add a and b
int binadd(int a, int b) {
    int carry = (a & b) << 1;
    int result = a ^ b;
    if (carry == 0)
        return result;
    else
        result = binadd(result, carry);

    return result;
}

// subtract b from a
int binsub(int a, int b) {
    // binadd(~b, 1) = two's complement of b, AKA -b
    return binadd(a, binadd(~b, 1));
}