The header <ctype.h> declares several functions useful for classifying and mapping characters.

The character argument to all functions is an int, the value of which is representable as an unsigned char or is the value of the macro EOF. If the argument has any other value, the behavior is undefined.

Only the "C" locale is supported by CrossWorks C, and thus the functions in this header are not affected by locales.

The term printing character refers to a member of a set of characters, each of which occupies one printing position on a display device; the term control character refers to a member of a set of characters that are not printing characters. All letters and digits are printing characters.

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 letter?
Conversion functions
tolower | Convert uppercase character to lowercase
toupper | Convert lowercase character to uppercase