Cache / caching - is it working?

[eluser]Bullit2k[/eluser]
Ok, from output.php in ci system libraries:

Code:

// Does the get_instance() function exist?
        // If not we know we are dealing with a cache file so we'll
        // simply echo out the data and exit.
        if ( ! function_exists('get_instance'))
        {
                     //problem for me here --- not entering this
                     //get_instance doesnt exist
                     //what's that? and how to make it exist?
            echo $output;
            log_message('debug', "Final output sent to browser");
            log_message('debug', "Total execution time: ".$elapsed);
            return TRUE;
        }

see my comments in above code...