C++ Programming Code Examples

C++ > Conversions Code Examples

Convert Hexadecimal to Decimal

Convert Hexadecimal to Decimal

To convert a number from hexadecimal format into equivalent decimal format in C++ programming, you have to ask to the user to enter the hexadecimal number to convert it into decimal number to display the equivalent value in decimal format as shown here in the following program.

Following C++ program ask to the user to enter any number in hexadecimal format to convert it into decimal, then display the result on the screen:
		
#include<iostream.h>
#include<stdlib.h>
#include<conio.h>
#include<math.h>

unsigned long convtodecnum(char hex[]);

void main()
{
    clrscr();
    unsigned long decnum;
    char hex[9];     // 8 characters for 32-bit Hexadecimal Number and one for ' '
	
    cout<<" Enter 32-bit Hexadecimal Number : ";
    cin>>hex;

    decnum = convtodecnum(hex);
    cout<<"Value in Decimal Number is "<<decnum<<"\n";
	
    getch();
}

unsigned long convtodecnum(char hex[])
{
    char *hexstr;
    int length = 0;
    const int base = 16;     // Base of Hexadecimal Number
    unsigned long decnum = 0;
    int i;
	
    // Now Find the length of Hexadecimal Number
    for (hexstr = hex; *hexstr != '\0'; hexstr++)
    {
	length++;
    }
	
    // Now Find Hexadecimal Number
    hexstr = hex;
    for (i = 0; *hexstr != '\0' && i < length; i++, hexstr++)
    {
	// Compare *hexstr with ASCII values
	if (*hexstr >= 48 && *hexstr <= 57)   // is *hexstr Between 0-9
	{
	    decnum += (((int)(*hexstr)) - 48) * pow(base, length - i - 1);
	}
	else if ((*hexstr >= 65 && *hexstr <= 70))   // is *hexstr Between A-F
	{
	    decnum += (((int)(*hexstr)) - 55) * pow(base, length - i - 1);
	}
	else if (*hexstr >= 97 && *hexstr <= 102)   // is *hexstr Between a-f
	{
	    decnum += (((int)(*hexstr)) - 87) * pow(base, length - i - 1);
	}
	else
	{
	    cout<<"Invalid Hexadecimal Number \n";

	}
    }
    return decnum;
}