isalnum
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | Defined in header  <ctype.h> | ||
| int isalnum( int ch ); | ||
Checks if the given character is an alphanumeric character as classified by the current C locale. In the default locale, the following characters are alphanumeric:
-  digits (0123456789)
-  uppercase letters (ABCDEFGHIJKLMNOPQRSTUVWXYZ)
-  lowercase letters (abcdefghijklmnopqrstuvwxyz)
The behavior is undefined if the value of ch is not representable as unsigned char and is not equal to EOF.
| Contents | 
[edit] Parameters
| ch | - | character to classify | 
[edit] Return value
Non-zero value if the character is an alphanumeric character, 0 otherwise.
[edit] Example
Demonstrates the use of isalnum() with different locales (OS-specific).
Run this code
#include <stdio.h> #include <ctype.h> #include <locale.h> int main(void) { unsigned char c = '\xdf'; // German letter ß in ISO-8859-1 printf("isalnum('\\xdf') in default C locale returned %d\n", !!isalnum(c)); setlocale(LC_CTYPE, "de_DE.iso88591"); printf("isalnum('\\xdf') in ISO-8859-1 locale returned %d\n", !!isalnum(c)); }
Output:
isalnum('\xdf') in default C locale returned 0
isalnum('\xdf') in ISO-8859-1 locale returned 1[edit] References
- C11 standard (ISO/IEC 9899:2011):
- 7.4.1.1 The isalnum function (p: 200)
 
- C99 standard (ISO/IEC 9899:1999):
- 7.4.1.1 The isalnum function (p: 181)
 
- C89/C90 standard (ISO/IEC 9899:1990):
- 4.3.1.1 The isalnum function
 
[edit] See also
| (C95) | checks if a wide character is alphanumeric (function) | 
| C++ documentation for isalnum | |
| ASCII values (hex) | characters | isalnum  | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 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 | 


