C program to convert Hexadecimal to Binary number system

Example

Input

Input hexadecimal: 1A

Output

Decimal number: 26

Logic to convert Hexadecimal to Binary number system

Hexadecimal to binary conversion is divided in three steps.

1. Extract each hex digits separately.
2. Find the binary of each extracted hex digit.
3. Store the binary equivalent of extracted hexadecimal number to final bin variable.

Repeat the above three steps till all hexadecimal digits are processed.

Hexadecimal to binary conversion table

Decimal	Binary	Hexadecimal
0	0000	0
1	0001	1
2	0010	2
3	0011	3
4	0100	4
5	0101	5
6	0110	6
7	0111	7
8	1000	8
9	1001	9
10	1010	A
11	1011	B
12	1100	C
13	1101	D
14	1110	E
15	1111	F

/**
 * C program to convert Hexadecimal to binary number system
 */

#include <stdio.h>
#include <string.h>

int main()
{
    char hex[17], bin[65] = "";
    int i = 0;

    /* Input hexadecimal number from user */
    printf("Enter any hexadecimal number: ");
    gets(hex);

    /* Extract first digit and find binary of each hex digit */
    for(i=0; hex[i]!='\0'; i++)
    {
        switch(hex[i])
        {
            case '0':
                strcat(bin, "0000");
                break;
            case '1':
                strcat(bin, "0001");
                break;
            case '2':
                strcat(bin, "0010");
                break;
            case '3':
                strcat(bin, "0011");
                break;
            case '4':
                strcat(bin, "0100");
                break;
            case '5':
                strcat(bin, "0101");
                break;
            case '6':
                strcat(bin, "0110");
                break;
            case '7':
                strcat(bin, "0111");
                break;
            case '8':
                strcat(bin, "1000");
                break;
            case '9':
                strcat(bin, "1001");
                break;
            case 'a':
            case 'A':
                strcat(bin, "1010");
                break;
            case 'b':
            case 'B':
                strcat(bin, "1011");
                break;
            case 'c':
            case 'C':
                strcat(bin, "1100");
                break;
            case 'd':
            case 'D':
                strcat(bin, "1101");
                break;
            case 'e':
            case 'E':
                strcat(bin, "1110");
                break;
            case 'f':
            case 'F':
                strcat(bin, "1111");
                break;
            default:
                printf("Invalid hexadecimal input.");
        }
    }

    printf("Hexademial number = %s\n", hex);
    printf("Binary number = %s", bin);

    return 0;
}

/*
Output :

Enter any hexadecimal number: 1a
Hexademial number = 1a
Binary number = 00011010
*/