isalnum(), isalpha(), iscntrl(), isdigit(), isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), and isxdigit()

Syntax

  #include <ctype.h>

  int isalnum (int ch);

  int isalpha (int ch);

...

  int isxdigit(int ch);

Description

These functions determine whether character ch belongs to a certain set of characters. The next table describes the character ranges tested by the functions.

Table 1. Testing Functions Character Range
Function	ch Test Range
`isalnum()`	Alphanumeric character ( `A-Z`, `a-z,` or `0-9)`
`isalpha()`	Alphabetic character ( `A-Z` or `a-z)`
`iscntrl()`	Control character ( `\000-\037` or `\177 (DEL)`)
`isdigit()`	Decimal digit ( `0-9`)
`isgraph()`	Printable character except space ( `!-~`)
`islower()`	Lower case letter ( `a-z`)
`isprint()`	Printable character ( `' '-~`)
`ispunct()`	Punctuation character ( `!-/`, `:-@`, `[-'` and `{-~`)
`isspace()`	White space character ( `' '`, `\f`, `\n`, `\r`, `\t` and `\v`)
`isupper()`	Upper case letter ( `A-Z`)
`isxdigit()`	Hexadecimal digit ( `0-9`, `A-F` or `a-f`)

Return

TRUE ( 1), if ch is in the character class; 0 otherwise.

See also

tolower()

toupper()