In this tutorial, we will write a program to convert an octal number into binary in C++. Before that, you must have knowledge of the following topics in C++.

**Binary number**

The binary numbers are based on 0 and 1, so it is a base 2 number. They are the combination of 0 and 1. For example, 1001, 110101, etc.

**Octal number**

The octal numbers are the numbers with base 8 and use the digits 0 to 7. Example: 8 in decimal is represented as 10 in octal, 25 as 31, and so on.

Let us go through a program for the Octal to Binary Conversion in C++.

**C++ Program to Convert Octal to Binary**

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | #include <iostream> #include <cmath> using namespace std; //user defined function int conversionFunc(int octNumber) { int deciNum = 0, binNumber = 0, i = 0; while (octNumber != 0) { deciNum += (octNumber % 10) *pow(8, i); ++i; octNumber /= 10; } i = 1; while (deciNum != 0) { binNumber += (deciNum % 2) *i; deciNum /= 2; i *= 10; } return binNumber; } //Main function int main() { int octNumber, result; cout << "Enter an octal number: "; cin >> octNumber; result = conversionFunc(octNumber); cout << "Equivalent Binary Number: " << result; return 0; } |

**Output:**

`Enter an octal number: 64`

Equivalent Binary Number: 110100

You may go through the vice versa conversion: