cctype functions

Each function below accepts a single integer argument. If the actual value is a character, C++ will convert it to its integer equivalent. Each is function returns a boolean, either true or false. The to functions return an integer which can be treated as a character.

• bool islower(int i) - returns true if chararacter represented by i is a lower case letter ('a'..'z')
• bool isupper(int i) - returns true if chararacter represented by i is an upper case letter ('A'..'Z')
• bool isalpha(int i) - returns true if islower(i) or isupper(i)
• bool isdigit(int i) - returns true if chararacter represented by i is a decimal digit ('0'..'9')
• bool isalnum(int i) - returns true if isalpha(i) or isdigit(i)
• bool iscntrl(int i) - returns true if chararacter represented by i is a control character
• bool isgraph(int i) - returns true if chararacter represented by i is any printing character except a space (' ')
• bool isprint(int i) - returns true if chararacter represented by i is any printing character including a space (' ')
• bool ispunct(int i) - returns true if chararacter represented by i is any printing character except isspace(i) and isalnum(i)
• bool isspace(int i) - returns true if chararacter represented by i is whitespace. Standard whitespace is :
  • space (' ')
  • formfeed ('\f')
  • newline ('\n')
  • carriage return ('\r')
  • tab ('\t')
  • vertical tab ('\v')
• bool isxdigit(int i) - returns true if chararacter represented by i is a hexadecimal digit ('0'..'9','A'..'F','a'..'f')
• int toupper(int i) - returns upper case equivalent to i if islower(i). All other values of i return i.
• int tolower(int i) - returns lower case equivalent to i if isupper(i). All other values of i return i.