Widget

RADIO AND CHECK BUTTONS: RADIO and CHECK BUTTONS are binary selection widgets. These are widgets which represent an on/off state. The difference between the two classifications is in a set of linked Radio Buttons only one of the associated buttons is allowed to be in the on state, where as with check buttons any or all of the buttons may be in the on state.
SLIDERS: SLIDERS are scroll buttons which are generally associated with List and Text Boxes.
ENTRY BOX: ENTRY BOXES define areas where text can be manually inserted.
BUTTONS: BUTTONS covers all classes of buttons outside the Check and Radio button classes. This includes, Menu, Push, and Toggle Buttons.
MENU OPTIONS: MENU OPTIONS are the list of options popped up whenever a menu button is activated.
LIST BOX: LIST BOXES are lists of text from which items can be selected (highlighted) and deselected (un-highlighted).
LABELS: LABELS are simple text widgets.
TEXT BOX: TEXT BOXES are areas in which text or information is displayed.
FRAMES: FRAMES define areas of a menu into which various widgets have been placed.

Murphy's Law

Murphy's law is a popular adage(an edge is a short) in Western culture that most likely originated at Edwards Air Force Base in 1948.
"The Law broadly states that things will go wrong in any given situation, if you give them a chance"
"If there's more than one way to do a job, and one of those ways will result in disaster, then somebody will do it that way."
It is most often cited as "Whatever can go wrong, will go wrong"
or alternately
"Whatever can go wrong will go wrong, and at the worst possible time,"
or
"Anything that can go wrong, will,"
or even
"If anything can go wrong, it will, and usually at the most inopportune moment"

The correct, original Murphy's Law reads:
"If there are two or more ways to do something, and one of those ways can result in a catastrophe, then someone will do it"
This is a principle of defensive design.
For example, you don't make a two-pin plug symmetrical and then label it THIS WAY UP; if it matters which way it is plugged in, then you make the design asymmetrical.

Features of GUI

Graphical user interfaces, such as Microsoft Windows and the one used by the Apple Macintosh, feature the following basic components:
Pointer : A symbol that appears on the display screen and that you move to select objects and commands. Usually, the pointer appears as a small angled arrow. Text - processing applications, however, use an I-beam pointer that is shaped like a capital I.
Pointing device : A device, such as a mouse or trackball, that enables you to select objects on the display screen.
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 your desk.
Desktop : The area on the display screen where icons are grouped is often referred to as the desktop because the icons are intended to represent real objects on a real desktop.
Windows: You can divide the screen into different areas. In each window, you can run a different program or display a different file. You can move windows around the display screen, and change their shape and size at will.
Menus : Most graphical user interfaces let you execute commands by selecting a choice from a menu.

Graphical User Interface

Abbreviated GUI (pronounced GOO-ee). A program interface that takes advantage of the computer’s graphic capabilities to make the program easier to use. Well-designed graphical user interfaces can free the user from learning complex command languages. On the other hand, many users find that they work more effectively with a command-driven interface, especially if they already know the command language.
OR
A GUI (usually pronounced GOO-ee) is a graphical (rather than purely textual) user interface to a computer. As you read this, you are looking at the GUI or graphical user interface of your particular Web browser. The term came into existence because the first interactive user interfaces to computers were not graphical; they were text-and-keyboard oriented and usually consisted of commands you had to remember and computer responses that were infamously brief. The command interface of the DOS operating system (which you can still get to from your Windows operating system) is an example of the typical user-computer interface before GUIs arrived. An intermediate step in user interfaces between the command line interface and the GUI was the non-graphical menu-based interface, which let you interact by using a mouse rather than by having to type in keyboard commands. Graphical user interfaces, such as Microsoft windows and the one used by the Apple Machine tosh, feature the following basic components: Pointer: A symbol that appears on the display screen and that you move to select objects and commands. Usually, the pointer appears as a small angled arrow. Text-processing applications, however, use an I-beam-pointer that is shaped like a capital I. pointing device: A device, such as a mouse or trackball, that enables you to select objects on the display screen. 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 your desk. desktop: The area on the display screen where icons are grouped is often referred to as the desktop because the icons are intended to represent real objects on a real desktop. windows: You can divide the screen into different areas. In each window, you can run a different program or display a different file. You can move windows around the display screen, and change their shape and size at will. menus: Most graphical user interfaces let you execute commands by selecting a choice from a menu.
Today's major operating systems provide a graphical user interface. Applications typically use the elements of the GUI that come with the operating system and add their own graphical user interface elements and ideas. A GUI sometimes uses one or more metaphors for objects familiar in real life, such as the desktop, the view through a window, or the physical layout in a building. Elements of a GUI include such things as: windows, pull-down menus, buttons, scroll bars, iconic images, wizards, the mouse, and no doubt many things that haven't been invented yet. With the increasing use of multimedia as part of the GUI, sound, voice, motion video, and virtual reality interfaces seem likely to become part of the GUI for many applications. A system's graphical user interface along with its input devices is sometimes referred to as its "look-and-feel." The first graphical user interface was designed by Xerox corporation Palo Alto Research Center in the 1970s, but it was not until the 1980s and the emergence of the Apple Macintosh that graphical user interfaces became popular. One reason for their slow acceptance was the fact that they require considerable CPU power and a high-quality monitor, which until recently were prohibitively expensive. In addition to their visual components, graphical user interfaces also make it easier to move data from one application to another. A true GUI includes standard formats for representing text and graphics. Because the formats are well-defined, different programs that run under a common GUI can share data. This makes it possible, for example, to copy a graph created by spreadsheet program into a document created by a word processor.
When creating an application, many object-oriented tools exist that facilitate writing a graphical user interface. Each GUI element is defined as a class widgets from which you can create object instances for your application. You can code or modify prepackaged methods that an object will use to respond to user stimuli. Many DOS programs include some features of GUIs, such as menus, but are not graphics based. Such interfaces are sometimes called graphical character-based user interfaces to distinguish them from true GUIs.