The **`iswalnum()` function** checks whether or not the given wide character is an #key# alphanumeric character: uppercase/lowercase letter or decimal digits #key#.



# Library
```c
#include <wctype.h>
```

# Syntax
The function prototype is as follows:
```c
int iswalnum(wint_t ch);
```
`ch`: wide character to be checked.

## Return Value
The function returns an integer value:
- If the integer returned is non-zero (true), it means `ch` is a letter or a digit.
- If the integer returned is zero (false), it means `ch` is not a letter or a digit.

# Code

#include <stdio.h>
#include <stddef.h>
#include <wctype.h>
#include <wchar.h>

int main ()
{
  int i=0;
  wchar_t str[] = L"Earth_123!";
  while (str[i])
  {
    if (iswalnum(str[i])) //if a letter or a digit, non-zero(true) value is returned
      wprintf (L"%lc is an alphanumeric character\n", str[i]);
    else  //not a letter and not a digit
      wprintf (L"%lc is not an alphanumeric character\n", str[i]);
    i++;
  }
  return 0;
}

What is iswalnum() in C?

Checks if a wide character is alphanumeric, returning non-zero if true, zero if false.