C Standard Library Reference Guide series (2) ctype. h

Http://www.acm.uiuc.edu/webmonkeys/book/c_guide/2.2.html.

Author: Eric Huss

Chinese translator: Liu jinhong poechant

Copyright Disclaimer: the original text in this article is copyrighted by Eric Huss, and the Chinese translation is copyrighted by poechant. Reprinted please indicate from "LIU Da's csdn blog": http://blog.csdn.net/poechant

2. ctype. h

Character header files are used to test characters and convert characters. A control character that references another character is not a printable character set. In the ASCII character set, all characters 0x0 to 0x1 F and 0x7f (delete key) are control characters, and the printable characters are from 0x20 (Space) to 0x7e (Tilde ).

Function:

Isalnum ();

Isalpha ();

Iscntrl ();

Isdigit ();

Isgraph ();

Islower ();

Isprint ();

Ispunct ();

Isspace ();

Isupper ();

Isxdigit ();

Tolower ();

Toupper ();

2.1. Is... Functions

Statement:

Int isalnum (intCharacter);

Int isalpha (intCharacter);

Int iscntrl (intCharacter);

Int isdigit (intCharacter);

Int isgraph (intCharacter);

Int islower (intCharacter);

Int isprint (intCharacter);

Int ispunct (intCharacter);

Int isspace (intCharacter);

Int isupper (intCharacter);

Int isxdigit (intCharacter);

Like "is ..." And return a non-zero value (true) when the character meets the conditions ). If not, 0 (false) is returned ).

Condition:

Isalnum	English letters (A to Z, or A to Z), or Arabic numerals (0 to 9)
Isalpha	English letters (A to Z, or A to Z)
Iscntrl	Control characters (0x00 to 0x1f, or 0x7f)
Isdigit	Arabic numerals (0 to 9)
Isgraph	Any printable characters except spaces (0x21 to 0x7e)
Islower	Lowercase letters (A to Z)
Isprint	Printable characters (0x20 to 0x7e)
Ispunct	Punctuation Marks (printable characters except space and album)
Isspace	Blank characters (space, tab, carriage return, line break, vertical tab, form feed)
Isupper	Uppercase letters (A to Z)
Isxdigit	Hexadecimal number (0 to 9, A to F, or A to F)

2.2. to... Functions

Statement:

Int tolower (intCharacter);

Int toupper (intCharacter);

Like "..." To convert a single character. If a character Meets the appropriate conditions, it will be converted by this function. Otherwise, the function returns the original character.

Condition:

Tolower	If it is an upper-case letter, it is converted to a lower-case letter.
Toupper	If it is a lowercase letter, it is converted to the corresponding uppercase letter.

Instance:

# Include <ctype. h>

# Include <stdio. h>

# Include <string. h>

Int main (void)

{

Int loop;

Char string [] = "this is a test ";

For (loop = 0; loop <strlen (string); loop ++)

String [loop] = tolower (string [loop]);

Printf ("% s \ n", string );

Return 0;

}

(1) assert. HC standard Library Reference Guide series (2) ctype. HC standard Library Reference Guide series (3) errno. HC standard Library Reference Guide series (4) float. HC standard Library Reference Guide series (5) limits. HC standard Library Reference Guide series (6) locale. HC standard Library Reference Guide series (7) math. HC standard Library Reference Guide series (8) setjmp. HC standard Library Reference Guide series translations (9) signal. HC standard Library Reference Guide series translations (10) stdarg. HC standard Library Reference Guide series (11) stddef. HC standard Library Reference Guide series translations (12) stdio. H ()

Copyright Disclaimer: the original text in this article is copyrighted by Eric Huss, and the Chinese translation is copyrighted by poechant. Reprinted please indicate from "LIU Da's csdn blog": http://blog.csdn.net/poechant

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