C Programming/ctype.h/Function reference

isalnum

Prototype

int isalnum(int c);

Description

This function tests whether the character c is of class alpha or digit in the current locale.

isalpha

Prototype

int isalpha(int c);

Description

This function tests whether the character c is alphabetic in the current locale.

isblank

Prototype

int isblank(int c);

Description

This function tests whether the character c is a space or a tab in the current locale.

iscntrl

Prototype

int iscntrl(int c);

Description

This function returns true if c is a control character (that is, a character that is not a printing character).

isdigit

Prototype

int isdigit(int c);

Description

This function returns true if c is a decimal digit ('0' through '9').

isgraph

Prototype

int isgraph(int c);

Description

This function returns true if c is a character that has a glyph associated with it. Whitespace characters are not considered graphic.

islower

Prototype

int islower(int c);

Description

This function tests whether the character c is lowercase.

isprint

Prototype

int isprint(int c);

Description

This function returns true if c is a printing character. Printing characters include all the graphic characters, plus the space character.

ispunct

Prototype

int isalnum(int c);

Description

This function returns true if c is a punctuation character. This includes any printing character that is not alphanumeric or a space character.

isspace

Prototype

int isspace(int c);

Description

Returns true if c is a whitespace character. In the standard C locale, these are the valid space characters:

• Spaces
• Horizontal tabs
• Vertical tabs
• Newlines
• Formfeeds
• Carriage returns

isupper

Prototype

int isupper(int c);

Description

This function tests whether the character c is uppercase.

isxdigit

Prototype

int isxdigit(int c);

Description

This function tests whether the character c is a hexadecimal dight ('0' through 'F').

tolower

Prototype

int tolower(int c);

Description

This function transliterates an uppercase character to lowercase and returns it. If c is not an uppercase letter, c is returned unchanged.

toupper

Prototype

int toupper(int c);

Description

This function transliterates a lowercase character to uppercase and returns it. If c is not a lowercase letter, c is returned unchanged.