program to convert hexadecimal number into decimal .

//program to convert hexadecimal number into decimal .

#include <stdio.h>

#include <math.h>

#include <string.h>

void main()

{

    char hex_number[20];

    long long deci=0, place=1;

    int i = 0, val, len;

    /*

     * entering hexadecimal number from user

     */

    printf("Enter any hexadecimal number: \n");

    gets(hex_number);

     

    /* get/find the length of total number of hex digit (inputted as string)*/

    len = strlen(hex_number);

     len--;//it decreases the value of total length by 1 because we need one less value

       //  for multiplication. and array stores value from location 0

    /*

     * Converts the hexadecimal number to decimal number

     * using algorithm/formula for conversion

           deci = deci + (hex_number[i] * 16 ^ power)

     */

    for(i=0; hex_number[i]!='\0'; i++)

    {

        /*

         * Finds the decimal each equivalent hexadecimal digit

         following logic takes one character,converts into value as val  and then 

          goes for calculation.

         */

        switch(hex_number[i])

        {

            case '0':

                val = 0;

                break;

            case '1':

                val = 1;

                break;

            case '2':

                val = 2;

                break;

            case '3':

                val = 3;

                break;

            case '4':

                val = 4;

                break;

            case '5':

                val = 5;

                break;

            case '6':

                val = 6;

                break;

            case '7':

                val = 7;

                break;

            case '8':

                val = 8;

                break;

            case '9':

                val = 9;

                break;

            case 'a':

            case 'A':

                val = 10;

                break;

            case 'b':

            case 'B':

                val = 11;

                break;

            case 'c':

            case 'C':

                val = 12;

                break;

            case 'd':

            case 'D':

                val = 13;

                break;

            case 'e':

            case 'E':

                val = 14;

                break;

            case 'f':

            case 'F':

                val = 15;

                break;

        }

        deci += val * pow(16, len);

        len--;

    }

    printf("\Hexadecimal number = %s\n", hex_number);

    printf("equivalent Decimal number = %ld", deci);  

}

logics in mind:

-> hexadecimal number contains characters A,B,C,D,E, and F

-> we have to check and extract all characters one by one then we go for multiplication with increasing or

     decreasing power

->we have to go for sum

->display that sum