The <ctype.h> header file declares several functions
for testing characters. For each function, the argument is
an int whose value must be EOF or
representable as an unsigned char , and the return
value is an integer.
Functions
int isalnum(int c);
Returns a nonzero integer if the character passed to it is
an alphanumeric ASCII character. Otherwise, isalnum
returns 0.
int isalpha(int c);
Returns a nonzero integer if the character passed to it is
an alphabetic ASCII character. Otherwise, isalpha
returns 0.
int iscntrl(int c);
Returns a nonzero integer if the character passed to it is
an ASCII DEL character (177 octal, 0x7F hex) or any nonprinting
ASCII character (a code less than 40 octal, 0x20 hex). Otherwise,
iscntrl returns 0.
int isdigit(int c);
Returns a nonzero integer if the character passed to it is a
decimal digit character (0 to 9). Otherwise, isdigit
returns 0.
int isgraph(int c);
Returns a nonzero integer if the character passed to it is
a graphic ASCII character (any printing character except a space
character). Otherwise, isgraph returns 0.
int islower(int c);
Returns a nonzero integer if the character passed to
it is a lowercase alphabetic ASCII character. Otherwise,
islower returns 0.
int isprint(int c);
Returns a nonzero integer if the character passed to it is an
ASCII printing character, including a space character. Otherwise,
isprint returns 0.
int ispunct(int c);
Returns a nonzero integer if the character passed to it is
an ASCII punctuation character (any printing character that is
nonalphanumeric and greater than 40 octal, 0x20 hex). Otherwise,
ispunct returns 0.
int isspace(int c);
Returns a nonzero integer if the character passed to it
is white space. Otherwise, isspace returns 0. The
standard white space characters are:
- space (' ')
- form feed ('\f')
- new line ('\n')
- carriage return ('\r')
- horizontal tab ('\t')
- vertical tab ('\v')
int isupper(int c);
Returns a nonzero integer if the character passed to
it is an uppercase alphabetic ASCII character. Otherwise,
isupper returns 0.
int isxdigit(int c);
Returns a nonzero integer if the character passed to it
is a hexadecimal digit (0 to 9, A to F, or a to f). Otherwise,
isxdigit returns 0.
int tolower(int c);
Converts an uppercase letter to lowercase. c
remains unchanged if it is not an uppercase letter.
int toupper(int c);
Converts a lowercase letter to uppercase. c
remains unchanged if it is not a lowercase letter.
Previous Page | Next Page | Table of Contents | Index