<ctype.h> C Standard Library

The ctype.h header file includes numerous C standard library functions that declares several functions used for classify and transform individual characters. All functions of this library take a character as argument, we can either call individual character or their corresponding ASCII value(as int). All classification functions return non-zero value(true) if character satisfies the condition, otherwise zero(false). Transformation functions takes a character as argument and returns a character after transforming it. The tolower and toupper are the only transformation functions of ctype.h header file.

List of ctype Library Functions

Click on function names below to see detailed description of functions.

Function Description
isalnum It checks whether a character is an alphanumeric character or not
isalpha It checks whether a character is an alphabet or not
iscntrl It checks whether a character is control character or not
isdigit It checks whether a character is decimal digit character or not
isgraph It checks whether a character has graphical representation or not
islower It checks whether a character is lowercase alphabet or not
isprint It checks whether a character is printable character or not
ispunct It checks whether a character is punctuation character or not
isspace It checks whether a character is white-space character or not
isupper It checks whether a character is uppercase alphabet or not
tolower It converts an uppercase alphabet to a lowercase alphabet
toupper It converts a lowercase alphabet to an uppercase alphabet