> On which systems are they hidden? On most systems. There is a long-standing convention in the Unix-derived world that files and directories with names which

> On which systems are they hidden? On most systems. There is a long-standing convention in the Unix-derived world that files and directories with names which start with a dot (this also includes "." and "..") are hidden in directory listings. The main exception is Windows, which inherited its conventions from MS-DOS; the convention there is that files and directories with the "hidden" and/or "system" attributes set are hidden from directory listings by default.