2s'-complement.cpp

#include <iostream>

#define size 4
using namespace std;

int main()
{
    char binary[size + 1], one[size + 1], two[size + 1];
    int i, carry = 1, fail = 0;
    cout << " Enter a " << size << " bit binary number: ";
    cin >> binary;
    for (i = 0; i < size; i++)
    {
        if (binary[i] == '1')
        {
            one[i] = '0';
        }
        else if (binary[i] == '0')
        {
            one[i] = '1';
        }
        else
        {
            cout << "Error! Input the number of assigned bits." << endl;
            fail = 1;
            break;
        }
    }
    one[size] = '\0';

    for (i = size - 1; i >= 0; i--)
    {
        if (one[i] == '1' && carry == 1)
        {
            two[i] = '0';
        }
        else if (one[i] == '0' && carry == 1)
        {
            two[i] = '1';
            carry = 0;
        }
        else
        {
            two[i] = one[i];
        }
    }
    two[size] = '\0';
    if (fail == 0)
    {
        cout << " The original binary = " << binary << endl;
        cout << " Ones complement = " << one << endl;
        cout << " Twos complement = " << two << endl;
    }
}