3 CLASSIFICATION ACCORDING TO INTERFACE 33 The term user interface refers to

3 classification according to interface 33 the term

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The term user interface refers to the interaction between the user and computer and determines how easily the user can operate the computer. The underlying principle in O.S. design is to make complex tasks very simplefor the user to carry out.A.COMMAND - LINE BASED OPERATINGSYSTEM e.g. Ms Dos:The user interacts with a computer by typing a command at the prompt found on a command line. A computer reads instructions from the command line and executes them.For a command to be more user friendly, the words used should be descriptive verbs e.g. PRINT,COPY e.t.c. Unique abbreviations can also be used e.g. DIR, DEL, REN, CHKDSKe.t.c.The user must press the enter key for the command to be executed. A command line would be displayed as C:\> OR A:\>Command driven programs and operating systems accept commands in the form of specialwords or letters e.g. COPY, RENAME.Command – driven software is often more flexible than menu – driven software but more difficult to learn. The user must have knowledge of the availablecommands, what they do and therules governing how they should betyped.Command line interface.B. MENU DRIVEN INTERFACEe.g. Dos Shell or Dos Editor.This interface allows the user to select commands/options from a listor menu using keyboard or pointingdevice e.g. mouse. The simplest menu provides the user with a list of program commands displayed on-screen and a simple means of selecting between them.The user is presented with a choice and therefore does not need to remember any command. All the user has to do is to make a choice.Menu driven interface.C)GRAPHICAL USER INTERFACE (G.U.I.)Besides menus, GUI makes use of rectangular work areas called windows, graphical objects called icons and most commands are executed using a pointing device.These features are given an acronym WIMP which stands for Windows, Icons, Menus and Pointing devices.GUI allows you therefore to enter commands by pointing and clickingat objects that appear on the screen.GUIs such as Ms Windows have thefollowing basic components:i)Pointer – a symbol that appears on the display screen that you move to select objects and commands.ii)Pointing device – device such as mouse or trackball that enables you to select objects on the display screen.iii)Icons – small pictures that represent commands, files or windows. By moving the pointer to the icon and pressing a mouse button, you can execute a command or convert the icon into a window. You can also move the icons around the display screen as if they were real objects on a real desktop.iv)Windows – an area on the screen set aside for performingsome task. You can move, arrange, resize, open and exit windows on the desktop.v)Menus – a list of options from which commands can be selected to execute certain actions.
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