Virtual Machines

• A virtual machine takes the layered approach to its logical conclusion.  It treats hardware and the operating system kernel as though they were all hardware.
• A virtual machine provides an interface identical to the underlying bare hardware.
• The operating system creates the illusion of multiple processes, each executing on its own processor with its own (virtual) memory.
• The resources of the physical computer are shared to create the virtual machines.

1. CPU scheduling can create the appearance that users have their own processor.
2. Spooling and a file system can provide virtual card readers and virtual line printers.
3. A normal user time-sharing terminal serves as the virtual machine operator’s console.