Question

why we are using #include<ctype.h> in a pragramming

Answer 1

The <ctype.h> header file of the C Standard Library declares several functions that are useful for testing and mapping characters.

All the functions accepts int as a parameter, whose value must be EOF or representable as an unsigned char.

All the functions return non-zero (true) if the argument c satisfies the condition described, and zero(false) if not.

Library Functions

Following are the functions defined in the header ctype.h −

Sr.No.	Function & Description
1	int isalnum(int c) This function checks whether the passed character is alphanumeric.
2	int isalpha(int c) This function checks whether the passed character is alphabetic.
3	int iscntrl(int c) This function checks whether the passed character is control character.
4	int isdigit(int c) This function checks whether the passed character is decimal digit.
5	int isgraph(int c) This function checks whether the passed character has graphical representation using locale.
6	int islower(int c) This function checks whether the passed character is lowercase letter.
7	int isprint(int c) This function checks whether the passed character is printable.
8	int ispunct(int c) This function checks whether the passed character is a punctuation character.
9	int isspace(int c) This function checks whether the passed character is white-space.
10	int isupper(int c) This function checks whether the passed character is an uppercase letter.
11	int isxdigit(int c) This function checks whether the passed character is a hexadecimal digit.

The library also contains two conversion functions that accepts and returns an "int".

Sr.No.	Function & Description
1	int tolower(int c) This function converts uppercase letters to lowercase.
2	int toupper(int c) This function converts lowercase letters to uppercase.