- C++ Programming Examples
- C++ Programming Examples
- C++: Hello World
- C++: Get Input
- C++: Print Integer
- C++: Add two numbers
- C++: Add, Sub, Multiply, Div
- C++: Add Digits
- C++: Find Average and Percentage
- C++: Find Arithmetic Mean
- C++: Sum of n Natural Numbers
- C++: Sum of n Numbers
- C++: Square's Area and Perimeter
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- C++: Area and Circumference
- C++: Find Simple Interest
- C++: Fahrenheit to Celsius
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- C++: Print Prime Numbers
- C++: Reverse a Number
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- C++: Find Factorial of a Number
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- C++: First and Last Digit Sum
- C++: Product of Number Digits
- C++: Sum of Squares of Digits
- C++: Interchange Digits of Number
- C++ if-else Programs
- C++: Check Even or Odd
- C++: Check Prime or Not
- C++: Check Alphabet or Not
- C++: Check Vowel or Not
- C++: Check Leap Year or Not
- C++: Check Reverse equals Original
- C++: Check Perfect Number
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- C++: Check Armstrong or Not
- C++: Divisibility Test
- C++: Find Labor Wage
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- C++: Calculate Student Grade
- C++: Largest of Two Numbers
- C++: Largest of Three Numbers
- C++ Number Conversion
- C++: Decimal to Binary
- C++: Decimal to Octal
- C++: Decimal to Hexadecimal
- C++: Binary to Decimal
- C++: Binary to Octal
- C++: Binary to Hexadecimal
- C++: Octal to Decimal
- C++: Octal to Binary
- C++: Octal to Hexadecimal
- C++: Hexadecimal to Decimal
- C++: Hexadecimal to Binary
- C++: Hexadecimal to Octal
- C++ Pattern Programs
- C++: Pattern Programs
- C++: Print Diamond Pattern
- C++: Print Floyd's Triangle
- C++: Print Pascal's Triangle
- C++ Array Programs
- C++: 1D Array Program
- C++: Linear Search
- C++: Binary Search
- C++: Largest Element in an Array
- C++: Smallest Element in an Array
- C++: Find Second Largest Element
- C++: Find Second Smallest Element
- C++: Sum of All Elements
- C++: Multiply All Elements
- C++: Element in Even Position
- C++: Element in Odd Position
- C++: Print Even Numbers in Array
- C++: Print Odd Numbers in Array
- C++: Count Even or Odd Numbers
- C++: Sum of Even or Odd Numbers
- C++: Count Positive, Negative, Zero
- C++: Reverse an Array
- C++: Insert an Element
- C++: Delete an Element
- C++: Merge two Arrays
- C++: Bubble Sort
- C++: Selection Sort
- C++: Insertion Sort
- C++: Common Elements
- C++: 2D Array Programs
- C++: Add Two Matrices
- C++: Subtract Two Matrices
- C++: Transpose Matrix
- C++: Multiply Two Matrices
- C++: 3D Array Programs
- C++ String Programs
- C++: Print String
- C++: Find String Length
- C++: Compare Two Strings
- C++: Copy String
- C++: String Concatenation
- C++: Reverse a String
- C++: Delete Vowels from a String
- C++: Delete a Word from a String
- C++: Count Characters in a String
- C++: Count Words in a String
- C++: Frequency of Words
- C++: Remove Spaces from Strings
- C++: Sort a String
- C++: Uppercase to Lowercase
- C++: Lowercase to Uppercase
- C++: Swap Two Strings
- C++: Check the Anagram or Not
- C++: Capitalize All Words in a String
- C++: Get Numbers from a String
- C++ File Programs
- C++: Read a File
- C++: Write Content to a File
- C++: Append Data to a File
- C++: Read and Display File
- C++: Copy a File
- C++: Merge Two Files
- Count Characters in a File
- C++: Capitalize Every Word
- C++: List Files in Directory
- C++: Delete a File
- C++: Encrypt and Decrypt a File
- C++ Misc Programs
- C++: Print ASCII Value
- C++: Add Binary Numbers
- C++: Generate Random Numbers
- C++: Print a Smiling Face
- C++: Days into Years and Months
- C++: Add Two Numbers using Pointer
- C++: Print Fibonacci Series
- C++: Generate Armstrong Numbers
- C++: Find nCr and nPr
- C++: Get IP Address
- C++: Print Date and Time
- C++: Shutdown and Restart Computer
- C++ Programming Tutorial
- C++ Tutorial

# C++ Program to Add Two Binary Numbers

In this article, you'll learn and get code for the addition of two binary numbers entered by the user at run-time. Here I've created programs for binary number addition in the following ways:

**Note**: If you don't know the basic rules of binary number addition, you can
refer to its separate tutorial.

## In C++, add binary numbers using the string data type

The question is: write a program in C++ that receives two binary numbers as input and finds and prints their addition. The program given below uses string data types to do the task. The size() function returns the length of a string.

#include<iostream> using namespace std; int main() { string bin1, bin2, addRes; int len, carry, re, i; cout<<"Enter First Binary Number: "; cin>>bin1; cout<<"Enter Second Binary Number: "; cin>>bin2; len = bin1.size(); addRes = ""; carry = 0; for(i=(len-1); i>-1; i--) { re = carry; if(bin1[i] == '1') re = re+1; else re = re+0; if(bin2[i] == '1') re = re+1; else re = re+0; if(re%2==1) addRes = '1' + addRes; else addRes = '0' + addRes; if(re<2) carry = 0; else carry = 1; } if(carry!=0) addRes = '1' + addRes; cout<<"\nAddition Result = "<<addRes; return 0; }

Here is the initial output produced by the above C++ program:

Now enter 11101 as the first binary number and 11111 as the second. Here is its sample run with these user inputs:

The dry run of the above program with the same user input, that is, 11101 and 11111 as two binary numbers, goes like this:

- When the user enters these two binary inputs, it gets stored in
**bin1**and**bin2**variables respectively. That is of**string**type. Here is the character-by-character storage of**bin1 = "11101"**and**bin2 = "11111"**:- bin1[0] = '1'
- bin1[1] = '1'
- bin1[2] = '1'
- bin1[3] = '0'
- bin1[4] = '1'
- In a similar way, all characters get stored at their respective indexes for second input in
**bin2**.

- Now, using the statement
`len = bin1.size();`

The length of the first binary number gets initialized to**len**. Therefore**len=5**, because there are 5 characters available in**bin1** - The empty string, that is
**""**and an empty integer, that is**0**get initialized to two variables,**addRes**and**carry**, respectively. - Now the execution of the
**for**loop begins, starting with**i**'s value from len-1, 5-1, or 4. - Since the condition
**i>-1**or**4>-1**evaluates to be true, the program flow goes inside the loop and evaluates all the statement(s) available inside its body. - That is, the first statement
`re = carry;`

gets executed. Therefore**re=0** - Now that the condition (of first if), bin1[i] == "1" or bin[4] == "1" or "1" == "1" evaluates to True, re+1, 0+1, or 1 is initialized to re.
- Again, the condition (of the second if), bin2[i] == "1" or bin2[4] == "1" or "1" == "1" evaluates to True, so re+1, 1+1, or 2 is initialized to "re."
- Again, the condition (of the third if), re%2==1 or 2%2==1, evaluates to false, so program flow proceeds to its inverse, else, and '0' + addRes or '0' + "" or '0' is initialized to addRes.
- Again the condition (of fourth and last
**if**),**re<2**or**2<2**evaluates to be False, therefore program flow goes to**else**'s body and**1**gets initialized to**carry**. So**carry = 1** - Since all the statements get executed, the program flow goes to the increment part of the loop, and the value of i gets decremented. Now i=3
- Then the condition
**i>-1**or**3>-1**again evaluates to be true, therefore the program flow again goes inside the loop. This process continues, until the condition is evaluated as false. - After exiting from the loop, or when the condition (i>-1) evaluates to be false, "1" gets added before the
**addRes**variable, but only if carry does not equal 0. - In this way, the addition of two binary numbers gets calculated.

**Note**: The above program has a limitation. The limitation is that if the length of two entered binary inputs is not the same or equal, the
program doesn't work correctly. Therefore, here is another program created that works in all conditions, whether the length of binary number inputs
is equal or not.

#include<iostream> using namespace std; int main() { string str1, str2, sum=""; int len1, len2, i, j, ds=0; cout<<"Enter the First Binary Number: "; cin>>str1; cout<<"Enter the Second Binary Number: "; cin>>str2; len1 = str1.size(); len2 = str2.size(); i = len1 - 1; j = len2 - 1; while(i>=0 || j>=0 || ds==1) { ds = ds + ((i >= 0) ? str1[i] - '0' : 0); ds = ds + ((j >= 0) ? str2[j] - '0' : 0); sum = char(ds % 2 + '0') + sum; ds = ds/2; i--; j--; } cout<<"\nSum = "<<sum; return 0; }

Here is its sample run with user inputs **10110** and **110** as two binary numbers:

## In C++, addition of a binary number using the int data type

This is the program you need, I think. Because this program does not use any string type to do the task. This program is created with all its variables as int types. However, the output of both programs is identical.

#include<iostream> using namespace std; int main() { long int bin_one, bin_two, t1, t2; int i=0, rem=0, sum[16]; cout<<"Enter First Binary Number: "; cin>>bin_one; cout<<"Enter Second Binary Number: "; cin>>bin_two; t1 = bin_one; t2 = bin_two; while(bin_one !=0 || bin_two !=0) { sum[i++] = (bin_one % 10 + bin_two % 10 + rem) % 2; rem = (bin_one % 10 + bin_two % 10 + rem) / 2; bin_one = bin_one/10; bin_two = bin_two/10; } if(rem!=0) sum[i++] = rem; i--; cout<<endl<<t1<<" + "<<t2<<" = "; while(i>=0) cout<<sum[i--]; return 0; }

Here is its sample run with user input: 101010 as the first and 110111 as the second binary number:

## In C++, add binary numbers using a user-defined function

Here is another program that does the same task as the previous two programs but uses a user-defined function named addBinNums() that takes two arguments. One for the first binary number entered by the user at run-time, and the other for the second binary number.

#include<iostream> using namespace std; int i=0, sum[16]; void addBinNums(int, int); int main() { long int bin_one, bin_two; cout<<"Enter First Binary Number: "; cin>>bin_one; cout<<"Enter Second Binary Number: "; cin>>bin_two; addBinNums(bin_one, bin_two); cout<<endl<<"Sum = "; while(i>=0) cout<<sum[i--]; return 0; } void addBinNums(int b1, int b2) { int r=0; while(b1 !=0 || b2 !=0) { sum[i++] = (b1 % 10 + b2 % 10 + r) % 2; r = (b1 % 10 + b2 % 10 + r) / 2; b1 = b1/10; b2 = b2/10; } if(r!=0) sum[i++] = r; i--; }

Here is its sample run with user input, **110111** and **100011** as first and second binary numbers:

In the above program, the statement int i=0, sum[16]; is declared globally, which is outside of both the main() and addBinNums() functions. So that we can use these two variables throughout the program along with their updated values.

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