The line where the distinction should be drawn is not always clear. Many operating systems come pre-packaged with basic application software. Such software is not considered system software when it can be uninstalled usually without affecting the functioning of other software. Exceptions could be e.g. web browsers such as Internet Explorer where Microsoft argued in court that it was system software that could not be uninstalled. Later examples are Chrome OS and Firefox OS where the browser functions as the only user interface and the only way to run programs (and other web browsers can not be installed in their place), then they can well be argued to be (part of) the operating system and hence system software.