#include <ctype.h>
int isalnum(int c) - True if c is alphanumeric.
int isalpha(int c) - True if c is a letter.
int isascii(int c) - True if c is ASCII .
int iscntrl(int c) - True if c is a control character.
int isdigit(int c) - True if c is a decimal digit.
int isgraph(int c) - True if c is a graphical character.
int islower(int c) - True if c is a lowercase letter.
int isprint(int c) - True if c is a printable character.
int ispunct (int c) - True if c is a punctuation character.
int isspace(int c) - True if c is a space character.
int isupper(int c) - True if c is an uppercase letter.
int isxdigit(int c) - True if c is a hexadecimal digit.
int toascii(int c) - Convert c to ASCII .
tolower(int c) - Convert c to lowercase.
int toupper(int c) - Convert c to uppercase.