C Library - <ctype.h>

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Introduction

The ctype.h header file of the C Standard Library provides declares several functions useful for testing and mapping characters.

All the functions accepts int as a parameter, whose value must be EOF or representable as an unsigned char.

All the functions return non-zero (true) if the argument c satisfies the condition described, and zero if not.

Library Functions

Following are the functions defined in the header ctype.h:

S.N.Function & Description
1int isalnum(int c)
This function check whether the passed character is alphanumeric.
2int isalpha(int c)
This function check whether the passed character is alphabetic.
3int iscntrl(int c)
This function check whether the passed character is control character.
4int isdigit(int c)
This function check whether the passed character is decimal digit.
5int isgraph(int c)
This function check whether the passed character has graphical representation using locale.
6int islower(int c)
This function check whether the passed character is lowercase letter.
7int isprint(int c)
This function check whether the passed character is printable .
8int ispunct(int c)
This function check whether the passed character is punctuation character.
9int isspace(int c)
This function check whether the passed character is white-space.
10int isupper(int c)
This function check whether the passed character is uppercase letter.
11int isxdigit(int c)
This function check whether the passed character is hexadecimal digit.

The library also contains two conversion functions that also accept and return an "int"

S.N.Function & Description
1int tolower(int c)
This function convert uppercase letter to lowercase.
2int toupper(int c)
This function convert lowercase letter to uppercase.

Character Classes

S.N.Character Class & Description
1Digits
A set of whole numbers { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }
2Hexadecimal digits
This is the set of { 0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f }
3Lowercase letters
This is a set of { a b c d e f g h i j k l m n o p q r s t u v w x y z }
4Uppercase letters
A set of whole numbers {A B C D E F G H I J K L M N O P Q R S T U V W X Y Z }
5Letters
This is a set of lowercase letters and uppercase letters
6Alphanumeric characters
This is a set of Digits, Lowercase letters and Uppercase letters
7Punctuation characters
This is a set of ! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~
8Graphical characters
This is a set of Alphanumeric characters and Punctuation characters.
9Space characters
This is a set of tab, newline, vertical tab, form feed, carriage return, and space.
10Printable characters
This is a set of Alphanumeric characters, Punctuation characters and Space characters.
11Control characters
In ASCII, these characters have octal codes 000 through 037, and 177 (DEL).
12Blank characters
These are space and tab.
13Alphabetic characters
This is a set of Lowercase letters and Uppercase letters.


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