Program for decimal to octal conversion

Given a decimal number as input, we need to write a program to convert the given decimal number into equivalent octal number. i.e convert the number with base value 10 to base value 8. The base value of a number system determines the number of digits used to represent a numeric value. For example, the binary number system uses two digits 0 and 1, octal number system uses 8 digits from 0-7 and decimal number system uses 10 digits 0-9 to represent any numeric value.

Examples:

Input : 16
Output : 20

Input : 10
Output : 12

Input: 33
Output: 41

Algorithm:

  1. Store the remainder when the number is divided by 8 in an array.
  2. Divide the number by 8 now
  3. Repeat the above two steps until the number is not equal to 0.
  4. Print the array in reverse order now.

For Example:
If the given decimal number is 16.
Step 1: Remainder when 16 is divided by 8 is 0. Therefore, arr[0] = 0.
Step 2: Divide 16 by 8. New number is 16/8 = 2.
Step 3: Remainder when 2 is divided by 8 is 2. Therefore, arr[1] = 2.
Step 4: Divide 2 by 8. New number is 2/8 = 0.
Step 5: Since number becomes = 0. Stop repeating steps and print the array in reverse order. Therefore the equivalent octal number is 20.

Below diagram shows an example of converting the decimal number 33 to equivalent octal number.
decToOctal

Below is the implementation of above idea.

C/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 program to test above function
int main()
{
    int n = 33;

    decToOctal(n);

    return 0;
}

Java

// Java program to convert a decimal
// number to octal number
import java.io.*;

class GFG 
{
    // Function to convert decimal to octal
    static void decToOctal(int n)
    {
        // array to store octal number
        int[] octalNum = new int[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--)
            System.out.print(octalNum[j]);
    }
    
    // driver program
    public static void main (String[] args) 
    {
        int n = 33;
        decToOctal(n);    
    }
}

// Contributed by Pramod Kumar


Output:

41

This article is contributed by Harsh Agarwal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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