| Function | Header File | Description |
| isalnum | ctype.h | Tests for alphanumeric characters. |
| isalpha | ctype.h | Tests for alphabetic characters. |
| isascii | ctype.h | Tests if an integer is within the ASCII range. |
| isblank | ctype.h | Tests for the blank character attribute. |
| iscntrl | ctype.h | Tests for control characters. |
| _iscsym | ctype.h | Tests if a character is alphabetic or an underscore. |
| _iscsymf | ctype.h | Tests if a character is alphabetic, a digit, or an underscore. |
| isdigit | ctype.h | Tests for decimal digits. |
| isgraph | ctype.h | Tests for printable characters excluding the space. |
| islower | ctype.h | Tests for lowercase letters. |
| isprint | ctype.h | Tests for printable characters including the space. |
| ispunct | ctype.h | Tests for printable characters excluding the space. |
| isspace | ctype.h | Tests for white-space characters. |
| isupper | ctype.h | Tests for uppercase letters. |
| iswalnum | wctype.h | Tests for alphanumeric wide characters. |
| iswalpha | wctype.h | Tests for alphabetic wide characters. |
| iswblank | wctype.h | Tests a wide character for the blank character attribute. |
| iswctype | wctype.h | Tests a wide character for a specified property. |
| iswdigit | wctype.h | Tests wide characters for decimal digits. |
| iswgraph | wctype.h | Tests for printable wide characters excluding the space. |
| iswlower | wctype.h | Tests wide characters for lowercase letters. |
| iswprint | wctype.h | Tests for printable wide characters including the space. |
| iswpunct | wctype.h | Tests for printable wide characters excluding the space. |
| iswspace | wctype.h | Tests for white-space wide characters. |
| iswupper | ctype.h | Tests wide characters for uppercase letters. |
| isxdigit | ctype.h | Tests for hexadecimal digits. |
| iswxdigit | wctype.h | Tests wide characters for hexadecimal digits. |
| wctype | wchar.h | Returns the handle for a character class or property. |
| wcwidth | wchar.h | Determines number of display positions required to display a given wide character. |
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Alphabetical Listing of IBM C and C++
Compilers Functions and Macros