Virtual Machine System

A virtual machine (VM) is a software machine (computer) that executes programs like a real machine. Virtual machines are separated into two major categories, based on their use and degree of correspondence to any real machine. A system virtual machine provides a complete system platform which supports the execution of a complete operating system (OS). On the other hand, a process virtual machine is designed to run a single program, which means that it supports a single process.

■ Schedulability, Survivability and Robustness
The concept of scheduling is introduced as a deterministic scheduling approach able to guarantee a temporal constraint will be met; survivability is commonly used to describe computer-based systems designed to continue more or less fully operational with a reduction in throughput or an increase in response time in the event of some partial system, link, or combination failure thereof; robustness is the attribute of being able to resist unfavorable stresses, pressures, or changes in procedure or circumstance.