---
name: "iswalpha"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/iswalpha"
---

# iswalpha(3)

test for alphabetic wide character

## NAME

iswalpha - test for alphabetic wide character

## LIBRARY

Standard C library (*libc*, *-lc*)

## SYNOPSIS

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

**int iswalpha(wint\_t** *wc***);**

## DESCRIPTION

The **iswalpha**() function is the wide-character equivalent of the [**isalpha**(3)](/isalpha/3.md) function. It tests whether *wc* is a wide character belonging to the wide-character class "alpha".

The wide-character class "alpha" is a subclass of the wide-character class "alnum", and therefore also a subclass of the wide-character class "graph" and of the wide-character class "print".

Being a subclass of the wide-character class "print", the wide-character class "alpha" is disjoint from the wide-character class "cntrl".

Being a subclass of the wide-character class "graph", the wide-character class "alpha" is disjoint from the wide-character class "space" and its subclass "blank".

Being a subclass of the wide-character class "alnum", the wide-character class "alpha" is disjoint from the wide-character class "punct".

The wide-character class "alpha" is disjoint from the wide-character class "digit".

The wide-character class "alpha" contains the wide-character classes "upper" and "lower".

The wide-character class "alpha" always contains at least the letters 'A' to 'Z' and 'a' to 'z'.

## RETURN VALUE

The **iswalpha**() function returns nonzero if *wc* is a wide character belonging to the wide-character class "alpha". Otherwise, it returns zero.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **iswalpha**() | Thread safety | MT-Safe locale |

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

POSIX.1-2001, C99.

## NOTES

The behavior of **iswalpha**() depends on the **LC\_CTYPE** category of the current locale.

## SEE ALSO

[**isalpha**(3)](/isalpha/3.md), [**iswctype**(3)](/iswctype/3.md)