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C++ program to convert hexadecimal to octal number using class

Submitted by Shubh Pachori, on August 25, 2022

Problem statement

Given a hexadecimal value, we have to convert it into an octal value using the class and object approach.

Example:

Input:
Enter Hexadecimal: 23e

Output:
Octal Number: 32476

C++ code to convert hexadecimal to octal number using the class and object approach

#include <iostream>
#include<math.h>

using namespace std;

// create a class
class HexaToOctal {
  // private data member
  private:
    char hexa[20];

  // public functions
  public:
    // getHexa() function to get the hexadecimal
    void getHexa() {
      cout << "Enter HexaDecimal:";
      cin >> hexa;
    }

  // HToO() function to convert hexadecimal to octal
  int HToO() {

    // initialising int type variables for operations
    int index, length, decimal = 0, octal = 0;

    // for loop to find out length of the char array of hexa
    for (length = 0; hexa[length]; length++);

    // for loop to convert hexadecimal to decimal number
    for (index = 0; hexa[index]; index++, length--) {
      // if condition to check if the character
      // at index is a digit 
      if (hexa[index] >= '0' && hexa[index] <= '9') {
        // if it is a digit then power of 16 and 
        // length - 1 is multiplied to the digit at 
        // index in hexa after subtracting 0 from it
        decimal = decimal + (hexa[index] - '0') * pow(16, length - 1);
      }
      // if condition to check if it is a 
      // uppercase alphabet between A and F
      if (hexa[index] >= 'A' && hexa[index] <= 'F') {
        // if it is a uppercase alphabet between A and F then 
        // power of 16 and length - 1 is multiplied to the alphabet 
        // at index in hexa after subtracting 55 from it
        decimal = decimal + (hexa[index] - 55) * pow(16, length - 1);
      }

      // if condition to check if it is a 
      // lowercase alphabet between a and f
      if (hexa[index] >= 'a' && hexa[index] <= 'f') {
        // if it is a lowercase alphabet between a and f then 
        // power of 16 and length - 1 is multiplied to the alphabet 
        // at index in hexa after subtracting 87 from it
        decimal = decimal + (hexa[index] - 87) * pow(16, length - 1);
      }

    } 
    //  Now, variable decimal contains the decimal value 
    // of given hexadecimal number

    // reinitialising index with 1
    index = 1;

    // while loop to convert decimal to octal number
    while (decimal != 0) {
      // multiply index to the divided decimal by 
      // 8 and add it to the octal
      octal = octal + (decimal % 8) * index;

      // divide decimal by 8
      decimal = decimal / 8;

      // multiply index by 10 at every iteration
      index = index * 10;
    }
    // returning octal number
    return octal;
  }
};

int main() {
  // create an object
  HexaToOctal H;

  // int type variable to store octal number
  int octal;

  // function is called by the object to get hexadecimal
  H.getHexa();

  // HToO() function to convert 
  octal = H.HToO();

  cout << "Octal Number: " << octal;

  return 0;
}

Output

RUN 1:
Enter HexaDecimal:12
Octal Number: 22

RUN 2:
Enter HexaDecimal:123af
Octal Number: 221657

Explanation

In the above code, we have created a class HexaToOctal, one char type array data member hexa[20] to store the hexadecimal, and public member functions getHexa() and HToO() to store and convert the given hexadecimal to octal number.

In the main() function, we are creating an object H of class HexaToOctal, reading the hexadecimal given by the user using getHexa() function, and finally calling the HToO() member function to convert the given hexadecimal. The HToO() function contains the logic to convert the given hexadecimal number to an octal number and printing the result.

C++ Class and Object Programs (Set 2) »