The **`isxdigit`** **function** in C checks whether a character is a hexadecimal digit. Hexadecimal digits include the numbers $0-9$, uppercase letters $A-F$, and lowercase letters $a-f$.

To use the `isxdigit` function, you will need to include the `<ctype.h>` library in the program, as shown below:

```C
#include <ctype.h>
```

The prototype of the `isxdigit` function is shown below:

```C
int isxdigit(int c);
```

<h2>Parameters</h2>

The `isxdigit` function takes a single mandatory parameter, i.e., an integer that represents the character you want to check.

>Note: In the C language, characters are treated as integer values.


<h2>Return Value</h2>

If the argument passed to the `isxdigit` function is a valid hexadecimal character, then the function returns a non-zero integer; otherwise, it returns $0$. 

<h2>Example</h2>

The code below shows how the `isxdigit` function works in C:

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

int main() {
  
  // initializing string
  char str[] = "ae2k3F9J";

  // extracting characters
  for(int i = 0; i < strlen(str); i++)
  {

    // hexadecimal check
    if(isxdigit(str[i]))
    {
      printf("\'%c\' is a hexadecimal digit.\n", str[i]);
    }
    else
    {
      printf("\'%c\' is not a hexadecimal digit.\n", str[i]);
    }
    
  }

  return 0;
}

<h2>Explanation</h2>

First, the code initializes a character array. A `for-loop` iterates over the length of this array and extracts each character.

Each extracted character is then provided as an argument to the `isxdigit` function on `line 15`.

The `isxdigit` function proceeds to check if the character is a valid hexadecimal digit and outputs the result accordingly. 




What is isxdigit in C?

The isxdigit function checks if a character is a hexadecimal digit, returning non-zero if true.