2’s complement in C++

Program to find two’s complement of a binary number in C++

Problem –  Binary Number as a string, we have to print its 2’s complement.

2’s complement of a binary number is another binary number obtained by adding 1 to one’s complement.

Example:

Input: 101010                   

One’s complement the number: 010110

Algorithm:

  1. Take binary number input as string having length say size.
  2. Initialise int fail=0.
  3. Start loop from i=0 to i<size
    if binary[i]==1
    then one[i]=0
    else if binary[i]==0
    then one[i]=1
    else
    print “error! Enter binary number of assigned size”
    fail=1
    break
  4. Put null character in the string complement
    one[size] = ‘\0’
  5. If fail ==0 then print the ones complement.
  6. Start loop from i = size – 1 to i >= 0.
    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];
  7. Put null character in the string two.
    two[size] = ‘\0’;
  8. if fail == 0
    then print two’s complement.

 

Code:

//Program to find two's complement of a binary number
#include <iostream>

#define size 6 using namespace std;

int main() { char binary[size + 1], one[size + 1], two[size + 1]; int i, carry = 1, fail = 0; cout << " Input 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 << " After ones complement the value = " << one << endl; cout << " After twos complement the value = " << two << endl; } }