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A command line interface is a character-based interface in which a prompt is displayed on the screen at which the user types a command, followed by carriage return, at which point the command, if valid, is executed. An example of a command line interface is the DOS prompt.
A menu-driven interface presents various options to the user in the form of a list, from which commands may be selected. Types of menu include the menu bar, which displays the top-level options available to the user as a single line across the top of the screen; selecting one of these options displays a pull-down menu. Programs such as Microsoft Word use menus in this way.
In a graphical user interface programs and files appear as icons (small pictures), user options are selected from pull-down menus, and data is displayed in windows (rectangular areas), which the operator can manipulate in various ways. The operator uses a pointing device, typically a mouse, to make selections and initiate actions.
The study of the ways in which people interact with computers is a subbranch of ergonomics. It aims to make it easier for people to use computers effectively and comfortably, and has become a focus of research for many national and international programmes.
Green and red replaced blue and white as the national colours in 1910. The armillary sphere surrounds the shield of Portugal. Effective date: 30 June 1911.
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