Here is a basic definition:
http://www.pcmag.com/encyclopedia_term/0,1237,t=desktop+application&i=41158,00.asp[
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Basically, it is an application that runs on the computer directly instead of through a browser or a console. It has its own interface (the window that displays something) instead of being reliant on something else to display it. It is also usually installed or running from the computer itself (or a network share or some other attached data source).
As far as what items are common in desktop applications, I can give you the general list but applications can and do ignore the use of these common elements. Most applications, however, regardless of what code they were written in, have the following elements:
- A Window - a defined area where the application lives. This keeps the application in one place instead of having pieces all over. Usually the window is resizable on all edges.
- Window command buttons - Usually in the upper right there are three buttons (minimize, maximize/restore, and close). These have a common look and are in a common location so that they are easy to recognize and use.
- Application Icon - Most desktop applications have an icon that is specific to them so that it is easy to recognize what the application is by looking at the image. This icon is used in the task bar, on the shortcut to the application, on the executable of the application, and usually it is placed in the upper left of the application.
- Title Bar - This is the bar at the top of an application. This is where a user can click and drag the window around. It also usually tells the user something about the application (name, what document is open, etc.)
- Scrollbars - Usually scrollbars are present if the application needs them. Sometimes they disappear if they aren't needed anymore.
- Menu bar - this is where actions can be listed. Usually the items can be selected using the Alt key plus a letter. There are standard menu items like File, Window, and Help with standard items underneath them.
- Help and Context Help - Usually you can get help under the Help menu or by hitting F1. Applications used to provide context help (help specific to where you were or what you indicated) but that is becoming less popular.
As far as common pieces, that is about it. There are some other standard items out there that aren't necessaril common but are fairly prevalent. For example, the pin icon that allows you to pin and unpin a window. Microsoft has published a number of whitepapers on the subject and they have their own guidelines as well. Here is a link to one of their pages:
http://msdn.microsoft.com/en-us/library/ms997506[
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