C programming/ctype.h/Function reference

__NOTOC__ 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.