It is available in a 'thumbnail view' or within some other specialized viewing area on the screen. This reduced image usually fits into a 128 by 128 or a 117 by 117 pixel box, depending on the operating system used. In the case of graphic files most modern systems replace the generic icon with a reduced image of the graphic. In this case, the comments made in the previous paragraph concerning the icon as an art form also apply to file icons. In most systems and for most files these icons are generic images, representing the program used to create the file, or the file type. In certain views of folders or directories in a GUI all the documents or files are represented as icons, in addition to their file name and, in certain cases, other details. For instance, the GUI guidelines in one operating system might specify the need to create sets of 16, 32, and 48 pixel icons for any program while the GUI guidelines in another system might specify sets of 16, 24, 48 and 96 pixel icons for any program. This work is further complicated by the need to create several sets of function icons for several types of views in several types of operating systems, for any given program.

The icon must be original, distinctive, and tiny and it must be useful on a wide variety of monitors set at different resolutions. The creation of a good function icon can be considered as an art form in itself, comparable to that practiced in the past in the domain of miniature painting by old masters such as Joseph Severn and Charles-Francois Daubigny. Placing the cursor on the icon, and clicking (or double-clicking) a mouse, trackball or other button usually starts the function or program. Most computer functions in a GUI are represented by a function icon.

What is icon in computer