| Routine | Attributes | Description |
|---|
| isalnum | reentrant | Tests for an alphanumeric character. |
| isalpha | reentrant | Tests for an alphabetic character. |
| iscntrl | reentrant | Tests for a Control character. |
| isdigit | reentrant | Tests for a decimal digit. |
| isgraph | reentrant | Tests for a printable character with the exception of space. |
| islower | reentrant | Tests for a lowercase alphabetic character. |
| isprint | reentrant | Tests for a printable character. |
| ispunct | reentrant | Tests for a punctuation character. |
| isspace | reentrant | Tests for a whitespace character. |
| isupper | reentrant | Tests for an uppercase alphabetic character. |
| isxdigit | reentrant | Tests for a hexadecimal digit. |
| toascii | reentrant | Converts a character to an ASCII code. |
| toint | reentrant | Converts a hexadecimal digit to a decimal value. |
| tolower | reentrant | Tests a character and converts it to lowercase if it is uppercase. |
| _tolower | reentrant | Unconditionally converts a character to lowercase. |
| toupper | reentrant | Tests a character and converts it to uppercase if it is lowercase. |
| _toupper | reentrant | Unconditionally converts a character to uppercase. |
The character routines allow you to test individual characters for a variety of attributes and convert characters to different formats.