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# isalpha

From cppreference.com
< c‎ | string‎ | byte

Defined in header `<ctype.h>` |  |
int isalpha( int ch ); |  |

Checks if the given character is an alphabetic character, i.e. either an uppercase letter (`ABCDEFGHIJKLMNOPQRSTUVWXYZ`), or a lowercase letter (`abcdefghijklmnopqrstuvwxyz`).

In locales other than "C", an alphabetic character is a character for which isupper() or islower() returns true or any other character considered alphabetic by the locale. In any case, iscntrl(), isdigit(), ispunct() and isspace() will return false for this character.

The behavior is undefined if the value of `ch` is not representable as unsigned char and is not equal to EOF.

### [edit] Parameters

ch | - | character to classify

### [edit] Return value

Non-zero value (true) if the character is an alphabetic character, `0` (false) otherwise.

### [edit] Example

Demonstrates the use of isalpha() with different locales (OS-specific).

Run this code

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

    int main(void)
    {
        unsigned char c = '\xdf'; // German letter ß in ISO-8859-1

        printf("isalpha('\\xdf') in default C locale returned %d\n", !!isalpha(c));

        setlocale(LC_CTYPE, "de_DE.iso88591");
        printf("isalpha('\\xdf') in ISO-8859-1 locale returned %d\n", !!isalpha(c));
    }

Output:

    isalpha('\xdf') in default C locale returned 0
    isalpha('\xdf') in ISO-8859-1 locale returned 1

### [edit] See also

iswalpha | checks if a wide character is alphabetic (function) [edit]
C++ documentation for isalpha

ASCII values (hex) | characters | `iscntrl` `iswcntrl` | `isprint` `iswprint` | `isspace` `iswspace` | `isblank` `iswblank` | `isgraph` `iswgraph` | `ispunct` `iswpunct` | `isalnum` `iswalnum` | `isalpha` `iswalpha` | `isupper` `iswupper` | `islower` `iswlower` | `isdigit` `iswdigit` | `isxdigit` `iswxdigit`
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
0 - 8 | `0x00-0x08` | control codes (`NUL`, etc.) | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`
9 | `0x09` | tab (`\t`) | `≠0` | `0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`
10 - 13 | `0x0A-0x0D` | whitespaces (`\n`,`\v`,`\f`,`\r`) | `≠0` | `0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`
14 - 31 | `0x0E-0x1F` | control codes | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`
32 | `0x20` | space | `0` | `≠0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`
33 - 47 | `0x21-0x2F` | `!"#$%&'()*+,-./` | `0` | `≠0` | `0` | `0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0`
48 - 57 | `0x30-0x39` | `0123456789` | `0` | `≠0` | `0` | `0` | `≠0` | `0` | `≠0` | `0` | `0` | `0` | `≠0` | `≠0`
58 - 64 | `0x3a-0x40` | `:;<=>?@` | `0` | `≠0` | `0` | `0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0`
65 - 70 | `0x41-0x46` | `ABCDEF` | `0` | `≠0` | `0` | `0` | `≠0` | `0` | `≠0` | `≠0` | `≠0` | `0` | `0` | `≠0`
71 - 90 | `0x47-0x5A` | `GHIJKLMNOPQRSTUVWXYZ` | `0` | `≠0` | `0` | `0` | `≠0` | `0` | `≠0` | `≠0` | `≠0` | `0` | `0` | `0`
91 - 96 | `0x5B-0x60` | `[\]^_`` | `0` | `≠0` | `0` | `0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0`
97 -102 | `0x61-0x66` | `abcdef` | `0` | `≠0` | `0` | `0` | `≠0` | `0` | `≠0` | `≠0` | `0` | `≠0` | `0` | `≠0`
103-122 | `0x67-0x7A` | `ghijklmnopqrstuvwxyz` | `0` | `≠0` | `0` | `0` | `≠0` | `0` | `≠0` | `≠0` | `0` | `≠0` | `0` | `0`
123-126 | `0x7B-0x7E` | `{|}~` | `0` | `≠0` | `0` | `0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0`
127 | `0x7F` | backspace character (`DEL`) | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`

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