Hexadecimal to Decimal Conversion

“Hexadecimal to Decimal Conversion” is one of the classic programming problem exercise. Here, we are given a hexadecimal number, entered by user and our task is to write a program to convert the hexadecimal number to its equivalent decimal number.

Hexadecimal Numbers uses 16 values to represent the number. Numbers from 0-9 are expressed by digits 0-9 and 10-15 are represented by characters from A – F. 

Examples:

Hexadecimal = A
Decimal = 15
Hexadecimal = 4E
Decimal = 78

The steps required to convert hexadecimal number into decimal number is as follows:

1. Take Iterator = 1 and Decimal = 0.
2. Read the given hexadecimal string in reverse order character by character.
3. If the character encountered is digit between 0 to 9, then convert it into number by subtracting 48 from it and store the result into temp.
4. Else if the character encountered is between ‘A’ to ‘F’, then convert it into number by subtracting 55 from it and store the result into temp. 
5. Decimal = Decimal + temp*iterator.
6. Multiply the iterator by 16.
7. Repeat the steps from 2 to 6 for all the characters of the hexadecimal string.
8. Print the result.

C++ Program to convert Hexadecimal to Decimal is as follows:

/* C++ Program to Convert Hexadecimal Number to Decimal Number */  
#include<bits/stdc++.h>  
using namespace std;  
int main()  
{  
    /* Scan the Hexadecimal Number */  
    string Hexadecimal;  
    cout<<"Enter the Hexadecimal Number: ";  
    cin>>Hexadecimal;  
      
    /* Converting Hexadecimal to Decimal*/  
    int Decimal = 0;  
    int iterator = 1;  
    int size = Hexadecimal.length();  
    for(int i = size - 1; i >= 0; i--)  
    {  
        int temp;  
        if(Hexadecimal[i]>='A' && Hexadecimal[i]<='F')  
        {  
            temp = Hexadecimal[i] - 55;  
        }  
        else  
        {  
            temp = Hexadecimal[i] - 48;  
        }  
        Decimal = Decimal + temp*iterator;  
        iterator = iterator * 16;  
    }  
      
    /*Printing the result */  
    cout<<"The Decimal of "<<Hexadecimal<<" is "<<Decimal;  
}  

OUTPUT:
Enter the Hexadecimal Number: 4E
The Decimal of 4E is 78

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