ctype.h

character oriented function are stored in the header file ctype.h
isdigit()
this function is used to check wheather a given character is a digit are not.
Syntax:
int isdigit(char c);
isalpha()
this function is used to check wheather a given character is an alphabet or not
Syntax:
int isalpha(char c);
isupper()
this function is used to check wheather a given alphabet is in upper case or not
Syntax:
int isupper(char c); islower()
this function is used to check wheather a given alphabet is in lower case or not
Syntax:
int islower(char c); toupper()
this function is used to convert the lower case letter too upper case
Syntax:
char toupper(char c); tolower()
this function is used to convert the upper case letter to lower case
Syntax:
char tolower(char c);
ispunct()
this function is used to check wheather a given character is apunctuation character or not
Syntax:
int ispunct(char c);