<ctype.h>: Character Operations

Character classification routines
These functions perform character classification. They return true or false status depending whether the character passed to the function falls into the function's classification (i.e. isdigit() returns true if its argument is any value '0' though '9', inclusive). If the input is not an unsigned char value, all of this function return false.
int	isalnum (int __c)
int	isalpha (int __c)
int	isascii (int __c)
int	isblank (int __c)
int	iscntrl (int __c)
int	isdigit (int __c)
int	isgraph (int __c)
int	islower (int __c)
int	isprint (int __c)
int	ispunct (int __c)
int	isspace (int __c)
int	isupper (int __c)
int	isxdigit (int __c)

Character convertion routines
This realization permits all possible values of integer argument. The toascii() function clears all highest bits. The tolower() and toupper() functions return an input argument as is, if it is not an unsigned char value.
int	toascii (int __c)
int	tolower (int __c)
int	toupper (int __c)

Detailed Description

These functions perform various operations on characters.

#include <ctype.h>

Function Documentation

isalnum()

int isalnum

(

int

__c

)

Checks for an alphanumeric character. It is equivalent to (isalpha(c) || isdigit(c)).

isalpha()

int isalpha

(

int

__c

)

Checks for an alphabetic character. It is equivalent to (isupper(c) || islower(c)).

isascii()

int isascii

(

int

__c

)

Checks whether c is a 7-bit unsigned char value that fits into the ASCII character set.

isblank()

int isblank

(

int

__c

)

Checks for a blank character, that is, a space or a tab.

iscntrl()

int iscntrl

(

int

__c

)

Checks for a control character.

isdigit()

int isdigit

(

int

__c

)

Checks for a digit (0 through 9).

isgraph()

int isgraph

(

int

__c

)

Checks for any printable character except space.

islower()

int islower

(

int

__c

)

Checks for a lower-case character.

isprint()

int isprint

(

int

__c

)

Checks for any printable character including space.

ispunct()

int ispunct

(

int

__c

)

Checks for any printable character which is not a space or an alphanumeric character.

isspace()

int isspace

(

int

__c

)

Checks for white-space characters. For the avr-libc library, these are: space, form-feed ('\f'), newline ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v').

isupper()

int isupper

(

int

__c

)

Checks for an uppercase letter.

isxdigit()

int isxdigit

(

int

__c

)

Checks for a hexadecimal digits, i.e. one of 0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F.

toascii()

int toascii

(

int

__c

)

Converts c to a 7-bit unsigned char value that fits into the ASCII character set, by clearing the high-order bits.

Warning

Many people will be unhappy if you use this function. This function will convert accented letters into random characters.

tolower()

int tolower

(

int

__c

)

Converts the letter c to lower case, if possible.

toupper()

int toupper

(

int

__c

)

Converts the letter c to upper case, if possible.