ctype.h for string type?

[kenneth6]

ctype.h:
toupper(c), tolower(c): change case of char
isalphanum(c), isalpha(c), isdigit(c), ispunct(c), isspace(c), iscntrl(c), islower(c), isupper(c): boolean checks on type of char

i know this is for char type.

If the data i am using is in string type, how can i use these functions or do the similar tasks with the string type data?

[Laharl]

You can use a loop check each character in the string with the ctype functions. Beyond that, you're writing your own, though I imagine someplace there's a third party (aka nonstandard) C regular expressions library...