C++ Program to Convert Octal to Decimal2 min read

In this tutorial, we will write a program to convert octal numbers into decimal numbers in C++. Before that, you must have knowledge of the following topics in C++.

Octal number

The octal numbers are the numbers with base 8 and use the digits 0 to 7. Example: 8 in decimal is represented as 10 in octal, 25 as 31, and so on.

Decimal Number

These are the numbers with a base of 10, which ranges from 0 to 9. These numbers are formed with the combination of 0 to 9 digits such as 24, 345, etc.

Let us go through a program for the Octal to Decimal Conversion in C++.

C++ Program to Convert Octal to Decimal Number

The program takes a user input for an octal number. And then iterate using a while loop. You can also use for loop instead of while loop, the code remains the same. Lastly, display the equivalent decimal value.

One of the libraries math functions (pow()) is used. This function returns the value of power calculation maths. It is present in math.h header file.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
#include <iostream>
#include <math.h>
using namespace std;
 
int main()
{
   int oct, deci = 0, i = 0, rem;
 
   cout << "Enter the Octal Number: ";
   cin >> oct;
 
   while (oct != 0)
   {
      rem = oct % 10;
      deci = deci + (rem* pow(8, i));
      i++;
      oct = oct / 10;
   }
 
   cout << "Decimal Value: " << deci;
 
   return 0;
}

Output:

Enter the Octal Number: 10
Decimal Value: 8

You can also achieve the octal to decimal conversion using a function in C++. The way to do that is by creating a separate function where you pass the user entered octal value as an argument in a function.

After calculation, the function returns the decimal to the main function where the final result is displayed.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
//convert octal to decimal using function in C++
 
#include <iostream>
#include <cmath>
using namespace std;
 
// User defined function
int conversionFunc(int oct)
{
   int rem, deci = 0, i = 0;
 
   while (oct != 0)
   {
      rem = oct % 10;
      oct = oct / 10;
      deci = deci + (rem* pow(8, i));
      ++i;
   }
 
   return deci;
}
 
//MAIN FUNCTION
int main()
{
   int octal, result;
   cout << "Enter an octal number: ";
   cin >> octal;
 
   //calling a function
   result = conversionFunc(octal);
   cout << "Decimal value: " << result;
 
   return 0;
}

Output:

Enter an octal number: 10
Decimal value: 8

You may go through the following program for vice-versa:

MORE

Find the output ab, cd, ef, g for the input a,b,c,d,e,f,g in Javascript and Python

In this tutorial, we will write a program to find a pairs of elements from an array such that for the input [a,b,c,d,e,f,g] we will …
Read More

String Pattern Programs in C

In this tutorial, we will write various C pattern programs for String. Before that, you may go through the following topics in C. for loop …
Read More

Java Program to Find pair of Integers in Array whose sum is given Number

In this tutorial, we will write a program to find a pair of elements from an array whose sum equals a given number in java …
Read More

Program to Print Diamond Alphabet Patterns in C

In this tutorial, we will learn to write a C program to print Diamond patterns using alphabets/characters. However, in this tutorial, we will create a …
Read More

Half Diamond Pattern in C using Alphabets

In this tutorial, we will learn and code the half diamond alphabet patterns in C programming language. However, in this tutorial, we will create a …
Read More

Half Pyramid of Alphabets in C

In this tutorial, we will learn and code alphabet patterns in C programming language specifically the Half pyramid of alphabets in C programming. However, in …
Read More