Although some people continue to question whether multitasking is really necessary on a single-user computer, users definitely are ready for multitasking and can benefit from it. The popularity of MS-DOS RAM-resident programs such as Sidekick proves it. Although popups are not, strictly speaking, multitasking programs, they do allow fast context switching. This involves many of the same concepts as multitasking.
Under Windows, every program in effect becomes a RAM-resident popup. Several Windows programs can be displayed and running at the same time. Each program occupies a rectangular window on the screen, as shown in Figure 1-3 on the following page. The user can move the windows around on the screen, change their size, switch between different programs, and transfer data from one program to another. Because this display looks something like a desktop (in the days before the desk became dominated by the computer itself, of course), Windows is sometimes said to use a ”desktop metaphor“ for the display of multiple programs.