WordPress stores its current version in the
wp_version global variable. It is set in [wordpress root folder]/wp-includes/version.php. The global variable is a concatenated string, e.g., ‘2.0.0’.
WordPress provides the functions get_bloginfo($show = ”) and bloginfo($show = ”), defined in [wordpress root folder]/wp-includes/template-functions-general.php, as a template tags to retrieve or display the current version. Plugin and theme developers can use these tags to check or inform the users of any features specific to a WordPress version.
Back to full list of global variables.