Cctype header file Definition function instance

Cctype header file contains functions are mainly used to test the character value, the following is a random look for a table, but for beginners, how to use it, their own on the machine operation to solve, the latter two returned to the int type, indeed very unexpected, forced conversion, very simple.

Isalnum (c) True if C is a letter or a number

Isalpah (c) True if C is a letter

Iscntrl (c) True if C is a control character

IsDigit (c) True if C is a number

Isgraph (c) True if C is not a space

Islower (c) True if C is a lowercase letter

Isprint (c) True if C is a printable character

Ispunct (c) True if C is a punctuation mark

Isspace (c) True if C is a blank character

Isupper (c) True if C is a capital letter

Isxdigit (c) True if C is a hexadecimal number

ToLower (c) If C is a capital letter, it returns a lowercase letter, otherwise it returns C.

ToUpper (c) If C is a lowercase letter, return a larger letter form, otherwise return C.

I demonstrate the first and last, more representative.

#include <iostream> #include <cctype> using namespace std;         int main () {char C;     C= ' d ';     if (Isalnum (c)) {cout "C" "is a alpha or number";   else cout "C" "is a not alpha or number"; The output results are shown below: #include <iostream> #include <cctype> using namespace std;     int main () {char C;     c= ' D '; cout Char (ToLower (c));

The ToLower () function returns an integer type, so if you do not overload the function, the correct output is achieved by type conversion, so watch out.