Icon Definition

An icon is a small picture or symbol on a graphical user interface (GUI) that represents a program (or command), file, directory (also called a folder) or device (such as a hard disk or floppy). The term comes from the Greek word eikon, which means likeness, image or portrait.

A GUI is a user interface (i.e., a way of displaying things on a monitor screen) that uses windows, icons and menus and which can be manipulated by a mouse (or other pointing device, such as a trackball) in addition to (at least to some extent) the keyboard. This is in contrast to a command line interface (CLI), which uses text only and is accessed solely by a keyboard.

Icons were first developed in the 1970s at the Xerox Palo Alto Research Center (PARC) as a means of making computers easier for novices to use. Their first large-scale commercial application was on the Macintosh personal computer, which was introduced in 1984. Today virtually every major operating system employs icon-based GUIs.

Icons are used both on the desktop (including on the toolbars) and in within application programs. Examples of icons include a rectangle, sometimes with a bent corner (to represent a file), a file folder (to represent a directory), a picture of a trash can (to indicate a place to dispose of unwanted files and directories) and buttons on web browsers (for navigating to previous pages, for reloading the current page, etc.).

The mouse interacts with an icon in several ways. One is by the user clicking a button on the mouse when the mouse's cursor is positioned over the icon. This usually initiates some action, such as causing a program to run, a file to be displayed or a directory to open. On most systems the default is for the mouse button to be clicked twice in rapid succession, although on many systems this can be changed to be a single click.

The mouse can also drag icons. This is used for such activities as (1) rearranging icons on the desktop or within directories, (2) moving files and directories into or out of other directories, (3) copying files, directories or programs, (4) discarding files or directories (by dragging them to the trash can icon), (5) opening files, by dragging an icon representing a file into an icon representing an application (such as an HTML file into a web browser) and (6) moving objects around within programs (such as in a game, an art program or a graphical programming language tool).

The links in hypertext can be viewed as a special case of icons (i.e., a type of icon with limited functionality). Hypertext is text that contains words or phrases that can be clicked by a user to cause another page or document to be retrieved and displayed. Icons perform this function, but they can additionally be clicked to initiate other types of functions (e.g., executing commands) and can be dragged.

The creation of good icons is a highly specialized skill that requires both artistic talent and an understanding of usability concepts. Requirements for well crafted icons include originality, small size and suitability for a wide variety of display monitors set at various resolutions. Adding to the complications is the need to create multiple versions of each icon, for example for use when the cursor is over the icon.

Among the trends with regard to icons in recent years have been higher resolution and photograph-like realism. Sizes range from as little as 16 by 16 pixels to as great as 128 by 128 pixels, according to the operating system and display settings.

Another relatively recent advance has been the automatic generation of miniaturized images of the content of each file, not only of graphic image files but also of text and other types of files. This has the advantage of providing the user with a peek at the contents of a file (e.g., the first words of a text file) without having to open it.

Created June 19, 2005.
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