C++ Program For Decimal To Octal Conversion

The octal numbers are a base 8 number system that uses digits from 0-7 and the decimal numbers are a base 10 numbers system that uses 10 digits from 0-9 to represent any numeric value.

In this article, we will learn how to write a C++ program to convert a given decimal number into an equivalent octal number. i.e. convert the number with base value 10 to base value 8.

Algorithm to Convert Decimal Numbers to Octal in C++

1. Create an array to store the octal representation.
2. Run a loop till the number is not zero.
3. Extract the remainder by taking the mod of the number by 8 and store the remainder in the array as an octal digit.
4. Update the number by dividing it by 8 in each iteration.
5. Print the array in reverse order.

The below diagram shows an example of converting the decimal number 33 to an equivalent octal number.  

C++ Program to Convert Decimal Number To Octal Number

C++

// C++ program to convert a decimal
// number to octal number
#include <iostream>
using namespace std;

// Function to convert decimal
// to octal
void decToOctal(int n)
{
    // Array to store octal number
    int octalNum[100];

    // Counter for octal number array
    int i = 0;
    while (n != 0) {
        // Storing remainder in octal array
        octalNum[i] = n % 8;
        n = n / 8;
        i++;
    }

    // Printing octal number array in
    // reverse order
    for (int j = i - 1; j >= 0; j--)
        cout << octalNum[j];
}

// Driver Code
int main()
{
    int n = 33;

    // Function Call
    decToOctal(n);

    return 0;
}

Output

41

Explanation

If the given decimal number is 33.

• Step 1: Remainder when 33 is divided by 8 is 1. Therefore, arr[0] = 1. 
• Step 2: Divide 33 by 8. The new number is 33/8 = 4. 
• Step 3: Remainder, when 4 is divided by 8, is 4. Therefore, arr[1] = 4. 
• Step 4: Divide 4 by 8. The new number is 4/8 = 0. 
• Step 5: Since the number becomes = 0.

Stop repeating steps and print the array in reverse order. Therefore, the equivalent octal number is 41.

Complexity Analysis

• Time Complexity: O(log N)
• Space Complexity: O(N), since creating an array to store octal numbers.

Refer to the complete article Program for Decimal to Octal Conversion for more methods to convert Decimal numbers to Octal numbers.