by Dinesh Thakur

graphical user interfaceis fondly called "GUI" pronounced "gooey." The word "graphical" means pictures; "user" means the person who uses it; "interface" means what you see on the screen and how you work with it. So a graphical user interface, then, means that you (the user) get to work with little pictures on the screen to boss the computer around, rather than type in lines of codes and commands.

(GUI) An INTERACTIVE outer layer presented by a computer software product (for example an operating system) to make it easier to use by operating through pictures as well as words. Graphical user interfaces employ visual metaphors, in which objects drawn on the computer's screen mimic in some way the behaviour of real objects, and manipulating the screen object controls part of the program.

A graphical user interface usesmenusandicons(pictorial representations) to choose commands, start applications, make changes to documents, store files, delete files, etc. You can use the mouse to control a cursor or pointer on the screen to do these things, or you can alternatively use the keyboard to do most actions. A graphical user interface is considereduser-friendly.

The most popular GUI metaphor requires the user to point at pictures on the screen with an arrow pointer steered by a MOUSE or similar input device. Clicking the MOUSE BUTTONS while pointing to a screen object selects or activates that object, and may enable it to be moved across the screen by dragging as if it were a real object

Take, for example, the action of scrolling a block of text that is too long to fit onto the screen. A non-graphical user interface might offer a 'scroll' command, invoked by pressing a certain combination of keys, say CTRL+S. Under a GUI, by contrast, a picture of an object called a SCROLLBAR appears on the screen, with a movable button that causes the text to scroll up and down according to its position. Similarly, moving a block of text in a WORD PROCESSOR that employs a GUI involves merely selecting it by dragging the mouse pointer across it until the text becomes HIGHLIGHTED, then dragging the highlighted area to its intended destination.

There is now an accepted 'vocabulary' of such screen objects which behave in more or less similar ways across different applications, and even across different operating systems. These include: WINDOWS, ICONS, pull down and pop-up MENUS, BUTTONS and button bars, check boxes, dialogues and tabbed property sheets. Variants of these GUI objects are used to control programs under Microsoft Windows, Apple's MacOS, and on UNIX systems that have a windowing system such as Motif or KDE installed.

GUIs have many advantages and some disadvantages. They make programs much easier to learn and use, by exploiting natural hand-to-eye coordination instead of numerous obscure command sequences. They reduce the need for fluent typing skills, and make the operation of software more comprehensible and hence less mysterious and anxiety- prone. For visually-oriented tasks such as word processing, illustration and graphic design they have proved revolutionary.

On the deficit side, GUIs require far more computing resources than older systems. It is usual for the operating system itself to draw most of the screen objects (via SYSTEM CALLS) to relieve application programs from the overhead of creating them from scratch each time, which means that GUI-based operating systems require typically 100 to 1000 times more working memory and processing power than those with old text-based interfaces.

GUIs can also present great difficulties for people with visual disabilities, and their interactive nature makes it difficult to automate repetitive tasks by batch processing. Neither do GUIs automatically promote good user interface design. Hiding 100 poorly-chosen commands behind the tabs of a property sheet is no better than hiding them among an old-fashioned menu hierarchy - the point is to reduce them to 5 more sensible ones

Historically, the invention of the GUI must be credited to Xerox PARC where the first GUI based workstations - the XEROX STAR and XEROX DORADO - were designed in the early 1970s. These proved too expensive and too radical for commercial exploitation, but it was following a visit to PARC by Steve Jobs in the early 1980s that Apple released the LISA, the first commercial GUI computer, and later the more successful MACINTOSH. It was only following the 1990 release of Windows version 3.0 that GUIs became ubiquitous on IBM-compatible PCs.