<cctype> C字符函数

Character handling functions

This header declares a set of functions to classify and transform individual characters.

Functions

These functions take the int equivalent of one character as parameter and return an int that can either be another character or a value representing a boolean value: an int value of 0 means false, and an int value different from 0 represents true.

There are two sets of functions:

Character classification functions

They check whether the character passed as parameter belongs to a certain category:

isalnum

Check if character is alphanumeric (function )

isalpha

Check if character is alphabetic (function )

isblank

Check if character is blank (function )

iscntrl

Check if character is a control character (function )

isdigit

Check if character is decimal digit (function )

isgraph

Check if character has graphical representation (function )

islower

Check if character is lowercase letter (function )

isprint

Check if character is printable (function )

ispunct

Check if character is a punctuation character (function )

isspace

Check if character is a white-space (function )

isupper

Check if character is uppercase letter (function )

isxdigit

Check if character is hexadecimal digit (function )

Character conversion functions

Two functions that convert between letter cases:

tolower

Convert uppercase letter to lowercase (function )

toupper

Convert lowercase letter to uppercase (function )