Microsoft Virtualization Secrets

Tracing the Evolution of the Windows Client Operating System

Windows was not using multithreading but enabled the execution of multiple applications simultaneously using cooperative multitasking, where each application releases control of the CPU to allow others to run, hopefully!

Windows 1.0, introduced in late 1985, provided a very basic graphical interface that ran on top of the MS-DOS operating system, a hybrid approach that continued until Microsoft released its first 32-bit family of operating systems: Windows NT. Windows 1.0 provided the capability to run multiple applications at the same time and introduced many of the application window elements still used today, such as scroll bars, icons, dialog boxes, and even drop-down menus. It also included applications such as Paint, Calculator, and Notepad that are still present today, with some updates. Windows 2.0, which arrived two years later, took advantage of newer graphical technologies, 286 and 386 (Windows 2.1) processors, and more memory. Windows could now be overlapped and the control panel was introduced. Figure 2-1 shows the original Windows 2.0 interface with a few in-box applications running. Notice the icons at the bottom; this model returns to Windows much later in the form of the taskbar.

Figure 2-1: This screenshot of the Windows 2.0 interface shows some key elements that are still present in Windows today, such as the buttons to close, minimize, and maximize windows.

The shell is the primary user interface ...