• OS is sometimes known as a resource manager.

• the CPU, memory, and disk is a resource of the system

• The system performs as if it has a very large number of virtual CPU. (Time-slicing)
  • Turning a single CPU (or a smallset of them) into a seemingly infinite number of CPUs and thus allowing many programs to seemingly run at once is what we call virtualizing the CPU
• file system
  • the software in the operating system, that usually manages the disk

Virtualization

• hardware virtualization
  • one that based on the use of a hypervisor (ESX, Hyper-V)
  • one that functions as a software package running on top of host OS (VMware Server, Parallels Desktop).

Virtual Memory

Point

• transparency
  • invisible to the running program. the program shouldn’t be aware of the fact that memory is virtualized
  • the program behaves as if it has its own private physical memory.
• efficiency
  • not using too much memory for structures needed to support virtualization
• protection