| Classification functions | |
| isalnum | Is character alphanumeric? |
| isalpha | Is character alphabetic? |
| isblank | Is character a space or horizontal tab? |
| iscntrl | Is character a control character? |
| isdigit | Is character a decimal digit? |
| isgraph | Is character any printing character except space? |
| islower | Is character a lowercase letter? |
| isprint | Is character printable? |
| ispunct | Is character a punctuation mark? |
| isspace | Is character a whitespace character? |
| isupper | Is character an uppercase letter? |
| isxdigit | Is character a hexadecimal digit? |
| Conversion functions | |
| tolower | Convert uppercase character to lowercase |
| toupper | Convert lowercase character to uppercase |