Windows 95/98

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Windows 9X Application Support

Virtual Machines

Programs exist in virtual machines (VM). A virtual machine is an environment created by the operating system and the processor which simulates a full computer's resources (disk controllers, timers, and such). The virtual machine appears to a program as a full computer, so the program has virtual access to hardware and all other resources.

Virtual machines make programming easier. The programmer does not have to worry about tracking another program's use of hardware. The program makes a call to a virtual device. The operating system keeps track of the programs and hardware and determines which resources each program has at its disposal.

Virtual machines in Windows 95 are created to operate in Ring 3.

Virtual Machines in Windows 95

All Windows 95-based programs operate in a Virtual Machine (VM). There are different VMs in use with Windows 95.

Windows 95 has one System VM and can have multiple Microsoft MS-DOS̉ VMs. The System VM contains:

  1. Base system components (Kernel, User, GDI)
  2. An address space shared by 16-bit Windows-based programs.
  3. A separate address space for each 32-bit Windows-based program.