Windows executes your application in a secure environment that includes the support services your application needs to execute efficiently and with a minimum of problems. This environment is a flat virtual address space that can be as large as 2 gigabytes, providing you have enough available disk space. While executing, your program is protected by Windows from damaging other applications and from being damaged by other applications.
The operating system uses preemptive multitasking to control how much processor time each application uses. Instead of waiting for an application to voluntarily yield control of the computer back to the operating system, Windows allocates a period of processor time to the application and regains control when that period has expired. This prevents a program with an infinite loop from hanging the computer. If your program hangs, you can easily and safely stop it by using the Windows task manager. (For information about using this or any other feature of Windows, see the manuals that came with the operating system.)
Because you can use one application while another continues to execute, you can make better use of your own time. For example, you can use the visual development environment to edit the source for one project while another project is building, or use Microsoft Excel to prepare a graph for data that your program is busy producing. And if your computer has multiple processors and you are using Windows NT 4 or Windows 2000, the computation-intensive program producing your data might be executing on an otherwise idle processor, making it less likely that your other work will slow it down.