Another challenge is that many students have only ever used a GUI interface like MicrosoftWindows so there are some very strong mental models that have to be broken down and replaced. For example, the notion that data files are distinct from executable files; that a file can be opened by applications other than the one that automatically opens when you double-click a file icon; that you are not limited by the menu options presented to you by a GUI interface, etc. This situation continues to be a challenge with the growing prevalence of mobile devices where the code which runs the software is hidden behind barriers put up by the operating system.