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

## Example 1: Convert Octal Number to Decimal

``````
#include <iostream>
#include <cmath>
using namespace std;

int octalToDecimal(int octalNumber);

int main(){
int octalNumber;
cout << "Enter an octal number: ";
cin >> octalNumber;
cout << octalNumber << " in octal = " << octalToDecimal(octalNumber) << " in decimal";

return 0;
}

// Function to convert octal number to decimal
int octalToDecimal(int octalNumber){
int decimalNumber = 0, i = 0, rem;
while (octalNumber != 0)
{
rem = octalNumber % 10;
octalNumber /= 10;
decimalNumber += rem * pow(8, i);
++i;
}
return decimalNumber;
}
``````

Output

```Enter an octal number: 2341
2341 in octal = 1249 in decimal
```

In the program, the octal number is stored in the variable octalNumber and passed to function `octalToDecimal()`.

This function converts the octal number passed by user to its equivalent decimal number and returns it to `main()` function.

## Example 2: Convert Decimal Number to Octal

``````
#include <iostream>
#include <cmath>
using namespace std;

int decimalToOctal(int decimalNumber);

int main(){
int decimalNumber;
cout << "Enter a decimal number: ";
cin >> decimalNumber;
cout << decimalNumber << " in decimal = " << decimalToOctal(decimalNumber) << " in octal";

return 0;
}

// Function to convert decimal number to octal
int decimalToOctal(int decimalNumber){
int rem, i = 1, octalNumber = 0;
while (decimalNumber != 0)
{
rem = decimalNumber % 8;
decimalNumber /= 8;
octalNumber += rem * i;
i *= 10;
}
return octalNumber;
}
``````
```Enter an decimal number: 78
78 in decimal = 116 in octal
```

In the program, the decimal number is stored in the variable decimalNumber and passed to function `decimalToOctal()`.

This function converts the decimal number passed by user to its equivalent octal number and returns it to `main()` function.

## C++ for Beginners: C++ Program to Convert Octal Number to Decimal and vice-versa

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