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C++ program to implement Full Adder

  • Difficulty Level : Expert
  • Last Updated : 19 Aug, 2021

Prerequisite : Full Adder
We are given three inputs of Full Adder A, B,C-IN. The task is to implement the Full Adder circuit and Print output i.e. sum and C-Out of three inputs.

Introduction : 
A Full Adder is a combinational circuit that performs an addition operation on three 1-bit binary numbers. The Full Adder has three input states and two output states. The two outputs are Sum and Carry.

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Here we have three inputs A, B, Cin and two outputs Sum, Cout. And the truth table for Full Adder is 

Logical Expression :

SUM  =  C-IN  XOR  ( A XOR B )
C-0UT= A B + B C-IN + A C-IN

Examples –

  1.        Input :   A=1, B=0,C-In=0
           Output : Sum=1, C-Out=0
           Explanation – 
           Here from logical expression Sum= C-IN XOR (A XOR B )  i.e. 0 XOR (1 XOR 0) =1 , C-Out= A B + B C-IN + A C-IN              i.e.,  1 AND 0 + 0 AND 0 + 1 AND 0 = 0 .
  2.      Input :    A=1, B=1,C-In=0
         Output:  Sum=0, C-Out=1

Approach :

  • Initialize the variables Sum and C_Out for storing outputs.
  • First we will take three inputs A ,B and C_In.
  • By applying  C-IN XOR (A XOR B ) we get the value of Sum.
  • By applying   A B + B C-IN + A C-IN we get the value of C_Out.


// C++ program to implement full adder
#include <bits/stdc++.h>
using namespace std;
// Function to print sum and C-Out
void Full_Adder(int A,int B,int C_In){
    int Sum , C_Out;
    // Calculating value of sum
    Sum = C_In ^ (A ^ B);
    //Calculating value of C-Out
    C_Out = (A & B) || (B & C_In) || (A & C_In);
   // printing the values
    cout<<"Sum = "<<Sum<<endl;
    cout<<"C-Out = "<<C_Out<<endl;
// Driver code
int main() {
    int A = 1;
    int B = 0;
    int C_In = 0;
    // passing three inputs of fulladder as arguments to get result function
    Full_Adder(A, B, C_In);
    return 0;


Sum = 1
C-Out = 0
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