Hexadecimal to Decimal in C

You can convert a hexadecimal number to a decimal number in C using the scanf function to input the hexadecimal value as a string and then using the strtol function to perform the conversion. Here’s a C program that demonstrates this:

#include <stdio.h>
#include <stdlib.h>

int main() {
    char hex[20]; // Assuming enough space for the hexadecimal representation
    long decimalNum;

    // Input a hexadecimal number as a string
    printf("Enter a hexadecimal number: ");
    scanf("%s", hex);

    // Convert hexadecimal to decimal
    decimalNum = strtol(hex, NULL, 16);

    printf("Decimal equivalent: %ld\n", decimalNum);

    return 0;
}

In this program:

1. We declare a character array hex to store the input hexadecimal number as a string and a long variable decimalNum to store the decimal equivalent.
2. We use the scanf function to input the hexadecimal number as a string.
3. We then use the strtol function to convert the hexadecimal string to a decimal number. The strtol function takes three arguments:

• The first argument is the string to convert (hex in this case).
• The second argument is a pointer to a character pointer, which we set to NULL because we don’t need to track the end of the parsed string.
• The third argument is the base of the conversion, which is 16 for hexadecimal.

1. Finally, we print the decimal equivalent.

Compile and run the program, and it will allow you to enter a hexadecimal number, convert it to decimal, and display the result.