ctype.h functions

Each function below accepts a single character argument and each is function returns 0 if false and non zero if true. The to functions return a character.

• isalnum -- tests for isalpha or isdigit
• isalpha -- tests for islower or isupper
• iscntrl -- tests for a control character
• isdigit -- tests for any decimal digit ('0'..'9')
• isgraph -- tests for any printing character except a space (' ')
• islower -- tests for any lower case letters ('a'..'z')
• 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')
• isupper -- tests for upper case letters ('A'..'Z')
• 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.