Character Handling: ctype.h

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Character Handling: ctype .h

These functions take int arguments, which should be able to be represented as either unsigned char values or as EOF ; the effect of supplying other values is undefined. In Table F.2, "true" is used as shorthand for "a non-zero value." Interpretation of some definitions depends on the current locale setting, which is controlled by the functions of locale.h .

Table  F.2. Character-handling functions.

Prototype	Description
int isalnum (int c);	Returns true if c is alphanumeric (alphabetic or numeric).
int isalpha (int c);	Returns true if c is alphabetic.
int iscntrl (int c);	Returns true if c is a control character, such as Ctrl+B.
int isdigit (int c);	Returns true if c is a digit.
int isgraph (int c);	Returns true if c is any printing character other than a space.
int islower (int c);	Returns true if c is a lowercase character.
int isprint (int c);	Returns true if c is a printing character.
int ispunct (int c);	Returns true if c is a punctuation character (any printing character other than a space or an alphanumeric character).
int isspace (int c);	Returns true if c is a whitespace character: space, newline, formfeed, carriage return, vertical tab, horizontal tab, or, possibly, other implementation-defined characters .
int isupper (int c);	Returns true if c is an uppercase character.
int isxdigit (int c);	Returns true if c is a hexadecimal-digit character.
int tolower (int c);	If the argument is an uppercase character, returns the lowercase version; otherwise , just returns the original argument.
int toupper(int c);	If the argument is a lowercase character, returns the uppercase version; otherwise, just returns the original argument.

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