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

Converting numbers from one base to another is a common task in computer programming.

In this tutorial, we will discuss how to convert octal numbers to decimal and vice versa using C++.

Octal to Decimal Conversion:

Octal numbers are base 8 numbers, which means they use 8 digits, i.e., 0, 1, 2, 3, 4, 5, 6, and 7.

To convert an octal number to decimal, we need to follow the below steps:

Take the octal number as input.
Initialize a variable named decimal to zero.
Multiply each digit of the octal number starting from the rightmost digit by increasing powers of 8 (starting from 8^0) and add the result to the decimal variable.
Repeat step 3 until all digits of the octal number have been processed.
The value of the decimal variable is the decimal equivalent of the octal number.

Let’s see the code for the same:

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
    int octal, decimal = 0, i = 0;
    cout<<"Enter an octal number: ";
    cin>>octal;
    while(octal != 0)
    {
        decimal += (octal%10) * pow(8,i);
        ++i;
        octal/=10;
    }
    cout<<"The decimal equivalent is: "<<decimal;
    return 0;
}

Decimal to Octal Conversion:

Decimal numbers are base 10 numbers, which means they use 10 digits, i.e., 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. To convert a decimal number to octal, we need to follow the below steps:

Take the decimal number as input.
Initialize a variable named octal to zero.
Divide the decimal number by 8 and keep track of the remainder.
Add the remainder to the rightmost position of the octal number.
Repeat step 3 and 4 until the quotient becomes zero.
The octal number is the result obtained by writing the remainders in reverse order.

Let’s see the code for the same:

#include<iostream>
using namespace std;
int main()
{
    int decimal, octal = 0, i = 1;
    cout<<"Enter a decimal number: ";
    cin>>decimal;
    while(decimal != 0)
    {
        octal += (decimal%8) * i;
        decimal /= 8;
        i *= 10;
    }
    cout<<"The octal equivalent is: "<<octal;
    return 0;
}