The user interface is, basically, what we see on the monitor outside of a particular application such as a word processor or a spreadsheet program. I have given, above, a rather crude yet, hopefully, functional definition of an operating system. The reader should be aware that the term probably cannot be accurately defined. In fact the dispute between the U. S. Department of Justice and Microsoft Corp. is, in part, over what actually constitutes an operating system. Probably the most important function of the operating system is the management of files.
Files are, arguably, the most important concept a competent computer user needs to master.
All information and all programs on a computer are stored in files. We will discuss files more fully later in this module. The two most prevalent operating systems are Microsoft Windows and Unix. In the earlier days of computers every computer had its own operating system. It soon became clear that this was not practical or desirable.