The number of inbetween layers and their contents

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Unformatted text preview: Graphical user interface or GUI (pronounced "gooey") is a user-friendly interface that is much easier to learn and use than a command-line interface. Unlike command-line interface in which commands are textual, GUI commands are graphical (pictorial). As shown in Figure 9.3 (refer to Chapter 9), a GUI provides to the user a screen full of graphic icons (small images on the screen) or menus and allows the user to make a rapid selection from the displayed icons or menus to give instructions to the computer. A point-and-draw device is normally used to rapidly point to and select a particular graphic icon or menu item from the multiple options displayed on the screen. For example, we saw that in a system that uses command-line interface, to delete a file named report.txt we need to type a command like "del report.txt.'" However, in a system that uses GUI, the same operation can be performed simply by using a mouse to drag the icon that represents the file until it is superimposed on an icon shaped like a trash can. Then releasing the mouse button that was used for dragging the file, causes the file to disappear into the bulging trash can. Shell The command interpreter of an operating system that serves as its user interface is often referred to as the shell because it forms the outer layer of an operating system covering the other modules of the operating system. The shell can be a command-line interface or GUI. It is also possible to have many different shells for the same operating system. For example, an operating system can have a command-line shell as well as a GUI shell allowing the users to switch from one shell to another. Beginners often find it convenient to work with GUI shell, whereas advanced users find it more convenient to work with command-line shell. Some operating systems also support multiple command-line shells. It is like supporting multiple JCLs and allowing the user to use a language that he/she is most comfortable with. For example, many Unix operating systems support three command-line shells known as C shell, Bourne shell, and Korn shell. Operating System Structure We have studied about the v...
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