Explain what checked exceptions are and how they are used in programming.

Checked exceptions are a type of exceptions in programming languages like Java that the compiler requires to be explicitly handled or declared in the method signature. If a method can throw a checked exception, the calling code must either handle it within a try-catch block or declare this exception in its throws.

This helps make the code more reliable, as the programmer is forced to consider handling potential errors, such as input-output errors or network issues.

Example in Java:

public void readFile(String path) throws IOException {
    FileReader file = new FileReader(path);
    // ... reading the file
}

public void process() {
    try {
        readFile("data.txt");
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Here, IOException is a checked exception, and it must be either handled or declared.