ctype.h

#ifndef _SYS_CTYPE_H
#define _SYS_CTYPE_H
 
// checks for alphanumeric character (isalpha || isdigit)
int isalnum(int c);
 
// checks for alphabetic character
int isalpha(int c);
 
// checks for a control character
int iscntrl(int c);
 
// checks for a digit (0 through 9)
int isdigit(int c);
 
// checks for any printable character except space
int isgraph(int c);
 
// checks for a lowerspace character
int islower(int c);
 
// checks for an upperspace character
int isupper(int c);
 
// checks for any printable character including space
int isprint(int c);
 
// checks for any printable character that is not a space or alphanumeric character
int ispunct(int c);
 
// checks for whitespace characters (\f,\n,\r,\t,\v)
int isspace(int c);
 
// checks for hexadecimal digits (0 through 9 A through F uppercase and lowercase)
int isxdigit(int c);
 
// checks  whether  c is a 7-bit unsigned char value that fits into the ASCII character set.
int isascii(int c);
 
// checks for a blank character; that is, a space or tab
int isblank(int c);
 
// If c is a lowercase letter, return its uppercase equivalent, otherwise just return c.
int toupper(int c);
// If c is an uppercase letter, return its lowercase equivalent, otherwise just return c.
int tolower(int c);
#endif