> For the complete documentation index, see [llms.txt](https://42-guide.gitbook.io/42-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://42-guide.gitbook.io/42-guide/piscine-life/c02/ft_str_is_alpha.md).

# ft\_str\_is\_alpha

**Objective:**

Create a function that checks whether a string contains only alphabetic characters (uppercase or lowercase). The function should return `1` if the string contains only alphabetic characters (or is empty) and `0` otherwise.

***

**Turn-in Requirements:**

* **Directory:** `ex02/`
* **File:** `ft_str_is_alpha.c`
* **Allowed Functions:** None

***

**Prototype:**

```c
int ft_str_is_alpha(char *str);
```

***

**Implementation:**

Here’s how you can implement the function:

```c
// File: ft_str_is_alpha.c

int ft_str_is_alpha(char *str)
{
    int i;

    i = 0;
    while (str[i] != '\0') // Loop through each character of the string
    {
        // Check if the character is not within 'a'-'z' or 'A'-'Z'
        if (!((str[i] >= 'a' && str[i] <= 'z') || (str[i] >= 'A' && str[i] <= 'Z')))
            return (0); // Return 0 if a non-alphabetic character is found
        i++;
    }
    return (1); // Return 1 if all characters are alphabetic or the string is empty
}
```

***

**Explanation:**

* **Input Parameter:**\
  The function takes a single parameter, `str`, which is a pointer to the first character of the input string.
* **Loop through the string:**\
  The `while` loop continues until the null terminator (`\0`) is reached, indicating the end of the string.
* **Check each character:**
  * The condition checks if the current character is **not** within the ranges `'a'` to `'z'` or `'A'` to `'Z'`.
  * If any character falls outside these ranges, the function immediately returns `0`.
* **Empty string:**\
  If the string is empty (i.e., `str[0] == '\0'`), the loop doesn’t execute, and the function returns `1` as required.

***

**Example Usage:**

```c
#include <stdio.h>

int ft_str_is_alpha(char *str);

int main()
{
    printf("%d\n", ft_str_is_alpha("Hello"));        // Output: 1
    printf("%d\n", ft_str_is_alpha("Hello123"));    // Output: 0
    printf("%d\n", ft_str_is_alpha(""));            // Output: 1
    printf("%d\n", ft_str_is_alpha("42Berlin"));    // Output: 0
    return 0;
}
```

* **Explanation of Outputs:**
  * `"Hello"`: All alphabetic characters → returns `1`.
  * `"Hello123"`: Contains non-alphabetic characters → returns `0`.
  * `""`: Empty string → returns `1`.
  * `"42Berlin"`: Contains numeric characters → returns `0`.

***

**Notes:**

* Remove or comment out the `main` function when submitting your code.
* Make sure your code adheres to the Norminette coding standards.
* Avoid including unnecessary files in your directory.


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