Full prototype:
int isalpha(int);  
Purpose and Notes:
Used to test whether or not the argument passed in is an alphabetic character according to the set locale. (A-Z and a-z in english locales)
Returns:
int- C-style true or false based on whether the character passed in was an alphabetical character or not.
Argument 1:
int- A character to be tested on if it is alphabetical or not in the set locale.