C++ Exercises: Convert a octal number to a hexadecimal number

Last update on April 07 2025 12:59:16 (UTC/GMT +8 hours)

78. Octal to Hexadecimal Conversion

Write a C++ program to convert an octal number to a hexadecimal number.

Visual Presentation:

Sample Solution:-

C++ Code :

#include<iostream>  // Include necessary libraries
#include<string.h>
#include<math.h>
using namespace std;  // Use the standard namespace

int main()  // Start of the main function
{
    // Declare arrays and variables for calculations
    int ar1[20], ar2[20], ar3[20];
    int h, i, j, k, l, x, fr, flg, rem, n1, n3;    
    float rem1, n2, n4, dno;
    char octal_num[20]; // Define a character array to store the octal number
    x = fr = flg = rem = 0;
    rem1 = 0.0;
    cout << "\n\n Convert any octal number to a hexadecimal number:\n"; // Prompt the user for octal to hexadecimal conversion
    cout << "------------------------------------------------------\n"; // Display separator line
    cout << " Input any octal number: ";
    cin >> octal_num;  // Read the octal number input by the user

    // Separate whole and fractional parts of the octal number
    for (i = 0, j = 0, k = 0; i < strlen(octal_num); i++)
    {
        if (octal_num[i] == '.')
        {
            flg = 1;
        }
        else if (flg == 0)
            ar1[j++] = octal_num[i] - 48;
        else if (flg == 1)
            ar2[k++] = octal_num[i] - 48;
    }

    x = j; // Store the count of whole part
    fr = k; // Store the count of fractional part

    // Convert whole part of octal to decimal
    for (j = 0, i = x - 1; j < x; j++, i--)
    {
        rem = rem + (ar1[j] * pow(8, i));
    }

    // Convert fractional part of octal to decimal
    for (k = 0, i = 1; k < fr; k++, i++)
    {
        rem1 = rem1 + (ar2[k] / pow(8, i));
    }

    rem1 = rem + rem1; // Combine the whole and fractional parts for calculation
    dno = rem1; // Store the combined decimal number
    n1 = (int)dno; // Extract the integer part
    n2 = dno - n1; // Extract the fractional part

    i = 0;
    // Convert the integer part to hexadecimal
    while (n1 != 0)
    {
        rem = n1 % 16;
        ar3[i] = rem;
        n1 = n1 / 16;
        i++;
    }

    j = 0;
    // Convert the fractional part to hexadecimal
    while (n2 != 0.0)
    {
        n2 = n2 * 16;
        n3 = (int)n2;
        n4 = n2 - n3;
        n2 = n4;
        ar1[j] = n3;
        j++;
        if (j == 4)
        {
            break;
        }
    }

    l = i; // Store the count of integer part
    cout << " The hexadecimal value of " << octal_num << " is: ";
    // Display the integer part in hexadecimal
    for (i = l - 1; i >= 0; i--)
    {
        if (ar3[i] == 10)
            cout << "A";
        else if (ar3[i] == 11)
            cout << "B";
        else if (ar3[i] == 12)
            cout << "C";
        else if (ar3[i] == 13)
            cout << "D";
        else if (ar3[i] == 14)
            cout << "E";
        else if (ar3[i] == 15)
            cout << "F";
        else
            cout << ar3[i];
    }

    h = j; // Store the count of fractional part
    cout << ".";
    // Display the fractional part in hexadecimal
    for (k = 0; k < h; k++)
    {
        if (ar1[k] == 10)
            cout << "A";
        else if (ar1[k] == 11)
            cout << "B";
        else if (ar1[k] == 12)
            cout << "C";
        else if (ar1[k] == 13)
            cout << "D";
        else if (ar1[k] == 14)
            cout << "E";
        else if (ar1[k] == 15)
            cout << "F";
        else
            cout << ar1[k];
    }
    cout << endl;    
}

Sample Output:

 Convert any octal number to a hexadecimal number:                     
------------------------------------------------------                 
 Input any octal number: 77                                            
 The hexadecimal value of 77 is: 3F.

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C++ program to convert an octal number to hexadecimal by first converting it to decimal and then to hexadecimal.
• Write a C++ program that reads an octal input and outputs its hexadecimal equivalent using intermediate conversion.
• Write a C++ program to compute the hexadecimal representation of an octal number by mapping through its decimal value.
• Write a C++ program that converts an octal string to hexadecimal by chaining octal-to-decimal and decimal-to-hexadecimal conversions.

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