###### C++ Functions

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

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

In this example, we 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 Number 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 1

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

##### Working

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 1

```Enter an octal number: 54
54 in octal = 101100```

##### Working

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

## Next Example

We hope that this Example helped you develop better understanding of the concept of "Convert Binary Number to Octal and vice-versa" in C++.

Keep Learning : )

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