C++ Code Example: convert decimal to octal number

To convert a number from the decimal system to the octal system in C++ programming language, the following code example can be used.

#include <iostream>
using namespace std;

int main() {
    int num, remainder, oct = 0, i = 1;

    cout << "Please enter a number: ";
    cin >> num;

    while (num != 0) {
        remainder = num % 8;
        num = num / 8;
        oct = oct + (remainder * i);
        i = i * 10;
    }

    cout << "Octal number : " << oct << endl;

    return 0;
}

Output

Please enter a number: 44
Octal number : 54

Code Explanation

This code converts a given decimal number to its octal equivalent. Here is a step-by-step explanation:

1. Input: The user is prompted to input a decimal number using the following line of code:

cout << "Please enter a number: ";
cin >> num;

2. Conversion: The conversion takes place in a while loop, which runs until the num becomes 0. In each iteration of the loop, the remainder when num is divided by 8 is calculated and stored in the remainder variable. The value of num is then updated to be num divided by 8. The value of oct is then updated as oct = oct + (remainder * i), where i is initially 1 and is multiplied by 10 in each iteration. This effectively adds the new remainder to the right side of the existing value of oct.
3. Output: The final value of oct is the octal equivalent of the input decimal number. This value is displayed on the console using the following line of code:

cout << "Octal number : " << oct << endl;