The Operating System and MultiWin

Windows NT provides the basic operating system components; adding Citrix MultiWin allows multiple concurrent users to ac-cess the WinFrame system. Essentially, users remotely control the WinFrame server in effect, they virtually sit at the console of the WinFrame server and share all systems resources with other concurrent users, making further use of the preemptive multi-tasking features of Windows NT.

MultiWin works with the Windows NT kernel to support multiuser sessions.

As illustrated in Figure 3-4 on page 58, preemptive multitasking means that the kernel (in this case, the Windows NT kernel plus MultiWin) acts as the gatekeeper and determines which thread gets processor time and when. Preemptive multitasking ensures that each thread gets its turn and that no particular thread or process can dominate system resources at the expense of other processes or threads, as opposed to a model that yields the processor to the application until execution has completed. In the latter scenario, an application that hangs can bring down the entire system.

FIGURE 3-4

Preemptive multitasking in a multiuser system

Preemptive multitasking is critical for a multiuser environment in which you want the system to perform like a single user system. It makes it seem to each user that he or she is the only person using the system.