Join our newsletter for the latest updates.

C++ Program to Convert Binary Number to Octal and vice-versa

In this example, you will learn to convert binary number to octal, and octal number to binary manually by creating a user-defined function.

To understand this example, you should have the knowledge of the following C++ programming topics:



Example 1: Program to Convert Binary to Octal

In this program, we will first convert the binary number to decimal. Then, the decimal number is converted to octal.

#include <iostream>
#include <cmath>

using namespace std;

int convertBinarytoOctal(long long);
int main()
{
    long long binaryNumber;

    cout << "Enter a binary number: ";
    cin >> binaryNumber;

    cout << binaryNumber << " in binary = " << convertBinarytoOctal(binaryNumber) << " in octal ";

    return 0;
}

int convertBinarytoOctal(long long binaryNumber)
{
    int octalNumber = 0, decimalNumber = 0, i = 0;

    while(binaryNumber != 0)
    {
        decimalNumber += (binaryNumber%10) * pow(2,i);
        ++i;
        binaryNumber/=10;
    }

    i = 1;

    while (decimalNumber != 0)
    {
        octalNumber += (decimalNumber % 8) * i;
        decimalNumber /= 8;
        i *= 10;
    }

    return octalNumber;
}

Output

Enter a binary number: 10001
10001 in binary = 21 in octal

The binary number entered by the user is passed to convertBinaryToOctal() function. And, this function converts the number to octal and returns to the main() function


Example 2: Program to Convert Octal to Binary

In this program, the octal number is converted to decimal at first. Then, the decimal number is converted to binary number.

#include <iostream>
#include <cmath>

using namespace std;

long long convertOctalToBinary(int);
int main()
{
    int octalNumber;

    cout << "Enter an octal number: ";
    cin >> octalNumber;

    cout << octalNumber << " in octal = " << convertOctalToBinary(octalNumber) << "in binary";

    return 0;
}

long long convertOctalToBinary(int octalNumber)
{
    int decimalNumber = 0, i = 0;
    long long binaryNumber = 0;

    while(octalNumber != 0)
    {
        decimalNumber += (octalNumber%10) * pow(8,i);
        ++i;
        octalNumber/=10;
    }

    i = 1;

    while (decimalNumber != 0)
    {
        binaryNumber += (decimalNumber % 2) * i;
        decimalNumber /= 2;
        i *= 10;
    }

    return binaryNumber;
}

Output

Enter an octal number: 54
54 in octal = 101100

The octal number entered by the user is passed to convertOctalToBinary() function. And, this function converts the number to binary and returns the main() function

Did you find this article helpful?