If it is a window system but the software may use a fixed screen size, then whether it is window or full screen depend what resolution is set, and may have a user option to set integer zoom. However, this is usually for a computer game, and if you can, it is best to allow the user specified size.
I don't like the websites to don't use the full width of the screen for text; the user can resize the window to put the width that they want instead. If a website does not use the full width, I will use the Stylish extension to override it.
However, many program doesn't need GUI, it can be command-line interface, and does not need to deal with screen space at all (and you can use for example "| less" if it doesn't fit on the screen and want to scroll through it).
I also think that a maximum password length of four digits is way too short, although maybe that can be reasonable as the minimum length.