What are the functions of the following header files: 

(i)  ctype.h

(ii)  string.h  

(i)   ctype.h: It is a header file that having character testing and conversion functions. 

For example isalpha (c) returns an int type data and verify if the argument c is alphabetic. It returns nonzero value if true; 0 or else. toascii(c ): is a conversion function described in ctype.h that changes value of argument to ascii.    

(ii)   string.h: It is also a standard header file that having string manipulation funcions.

For example strcmp(c1,c2) function compares two strings c1 and c2 lexicographically. It returns a negative value if c1c2.