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C++ program to implement full subtractor

  • Difficulty Level : Expert
  • Last Updated : 17 Aug, 2021

Prerequisite : Full Subtractor
Given three inputs of Full Subtractor A, B, Bin. The task is to implement the Full Subtractor circuit and Print output states difference (D) and Bout of three inputs.

Introduction :
The full subtractor is used to subtract three 1-bit numbers  which are minuend, subtrahend, and borrow, respectively. The full subtractor has three input states and two output states. The two outputs are difference and borrow.

Here we have three inputs A, B, Bin and two outputs D, Bout. And the truth table for full subtractor is 

Logical Expression : 

Difference = (A XOR B) XOR Bin
Borrow Out = Ā Bin + Ā B + B Bin

Examples –

     Input         :    0 0 1
     Output      :     Difference=1, B-Out=1
     Explanation :   According to logical expression Difference= (A XOR B) XOR Bin  i.e (0 XOR 0) XOR 1  =1 ,
      B-Out=Ā Bin + Ā B + B Bin  i.e.  1AND 1 + 1 AND 0 + 0 AND 1 = 1.

    Input         :    1 0 1
    Output      :     Difference=0, B-Out=0

Approach :

  • We will take three inputs A, B, Bin.
  • By applying (A XOR B) XOR Bin gives the Value of Difference.
  • By applying Ā Bin + Ā B + B Bin gives the value of B-Out.


//c++ code for above approach
#include <bits/stdc++.h>
using namespace std;
//function to print difference and borrow out
void Full_Subtractor(int A,int B,int Bin){
   // Calculating value of Difference
    int Difference = (A ^ B) ^ Bin;
    //calculating NOT  value of a
    int A1 = not(A);
    //Calculating value of B-Out
    int B_Out = A1 & Bin | A1 & B | B & Bin;
    //printing the values
    cout<<"Difference = "<<Difference<<endl;
    cout<<"B-Out = "<<B_Out<<endl;
//Driver code
int main() {
    int A = 1;
    int B = 0;
    int Bin = 1;
    // calling the function
    Full_Subtractor(A, B, Bin);
    return 0;


Difference = 0
B-Out = 0

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