islower() in C

The islower() function in C is part of the C Standard Library, and it is used to check if a given character is a lowercase letter in the ASCII character set. It takes an integer argument (typically representing a character) and returns an integer value, typically 1 (true) if the character is a lowercase letter and 0 (false) otherwise.

Here is the prototype of the islower() function:

int islower(int c);

• c: An integer representing a character.

Here’s an example of how to use islower():

#include <stdio.h>
#include <ctype.h>

int main() {
    char character = 'a';

    if (islower(character)) {
        printf("%c is a lowercase letter.\n", character);
    } else {
        printf("%c is not a lowercase letter.\n", character);
    }

    return 0;
}

In this example:

• We include the <ctype.h> header, which contains the islower() function.
• We check if the character 'a' is a lowercase letter using islower(). Since 'a' is indeed a lowercase letter, the program prints that it is.

You can use the islower() function to perform character-level checks in your C programs, especially when dealing with input validation or character classification.