c++ isalphanum

Step 1: The isalnum() function is a standard library function in C++ that is used to check whether a given character is alphanumeric or not. It takes a single argument of type char, which represents the character to be checked.

Step 2: The isalnum() function returns a non-zero value if the character is alphanumeric (i.e., a letter or a digit) and returns 0 otherwise.

Step 3: The return value of the isalnum() function can be used in conditional statements such as if-else or while loops to perform different actions based on whether the character is alphanumeric or not.

Step 4: Here is an example usage of the isalnum() function:

#include <iostream>
#include <cctype>

int main() {
    char ch = 'A';

    if (isalnum(ch)) {
        std::cout << "The character is alphanumeric." << std::endl;
    } else {
        std::cout << "The character is not alphanumeric." << std::endl;
    }

    return 0;
}

In this example, the character 'A' is checked using the isalnum() function. Since 'A' is an alphanumeric character, the output will be "The character is alphanumeric."

Step 5: The isalnum() function can be used to validate user input or perform specific actions based on the type of character encountered in a string or a loop.

Step 6: The isalnum() function is a part of the header file, so make sure to include this header file in your program in order to use the isalnum() function.