some cctype function prototypes
- bool islower(char c) returns true if c is a lower case letter ('a'..'z')
- bool isupper(char c) returns true if c is an upper case letter ('A'..'Z')
- bool isalpha(char c) returns true if c is an alphabetic character; islower or isupper
- bool isdigit(char c) returns true if c is a decimal digit ('0'..'9')
- bool isalnum(char c) returns true if c is an alphanumeric character; isalpha or isdigit
- bool isspace(char c) returns true if c is whitespace. Standard whitespace is :
- space (' ')
- formfeed ('\f')
- newline ('\n')
- carriage return ('\r')
- tab ('\t')
- vertical tab ('\v')
- bool iscntrl(char c) returns true if c is a control character
- bool isprint(char c) returns true if c is any printing character including a space (' ')
- bool isgraph(char c) returns true if c is any printing character except a space (' ')
- bool ispunct(char c) returns true if c is any printing character that is neither a space or alphanumeric (isalnum)
- bool isxdigit(char c) returns true if c is any hexadecimal digit character
- char toupper(char c) returns the upper case equivalent of a lower case argument. For all other arguments, it returns the argument itself.
- char tolower(char c) returns the lower case equivalent of an upper case argument. For all other arguments, it returns the argument itself.