C program to convert Hexadecimal to Binary number system

Write a C program to input hexadecimal number from user and convert to binary number system. How to convert hexadecimal number system to binary number system in C program. Logic to convert hexadecimal to binary number system in C programming.

Example

Input

Input hexadecimal: 1A

Output

Decimal number: 26

Required knowledge

Basic C programming, Switch case, For loop, Array

Hexadecimal number system

Hexadecimal number system is a base 16 number system. It uses 16 symbols to represent all numbers i.e. 0123456789ABCDEF

Binary number system

Binary number system is a base 2 number system. It uses 2 symbols to represent all numbers i.e. 0 and 1.

Logic to convert Hexadecimal to Binary number system

Hexadecimal to binary conversion is divided in three steps.

Extract each hex digits separately.
Find the binary of each extracted hex digit.
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

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

Program to convert hexadecimal to binary number system

/**
 * 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

Happy coding 😉