cctype functions

Each function below accepts a single character argument and each is function returns a boolean, either true or false. The to functions return an integer which can be treated as a character.

• islower - tests for any lower case letters ('a'..'z')
• isupper - tests for upper case letters ('A'..'Z')
• isalpha - tests for islower or isupper
• isdigit - tests for any decimal digit ('0'..'9')
• isalnum - tests for isalpha or isdigit
• iscntrl - tests for a control character
• isgraph - tests for any printing character except a space (' ')
• isprint - tests for any printing character including a space (' ')
• ispunct - tests for any printing character that is neither a space or isalnum
• isspace - tests for whitespace. Standard whitespace is :
  • space (' ')
  • formfeed ('\f')
  • newline ('\n')
  • carriage return ('\r')
  • tab ('\t')
  • vertical tab ('\v')
• isxdigit - tests for any hexadecimal digit character
• toupper - converts lower case to upper case for islower argument. All other argument characters remain unchanged.
• tolower- converts upper case to lower case for isupper argument. All other argument characters remain unchanged.