Virtual machine

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File:Windows 8 on Ubuntu 14.04 using VMware Workstation.png
Windows 8 running in a virtual machine on the Ubuntu OS

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Key points

  • A virtual machine is a software program which simulates a hardware platform. This means that it can allow a computer to run an Operating System within another operating system. The hosted OS acts as if it is running on a physical computer, but every hardware call is routed through the virtual machine.
  • Virtual machines contain the actions of the hosted Operating System because the software can control access to devices and networks.
  • Virtual machines use the processor of the computer directly (i.e. with the same machine code) but the programs run within the virtual machine can only interact with the hosted OS.
  • Virtual machines can also be created to run a program. The VM can protect the rest of the computer from being accessed by the program directly. This makes the program's execution much safer. This approach is called sandboxing. Sandboxing is used with Java, Python, Javascript and many other languages to separate the code being executed from the host computer.
  • Examples of virtual machines include PC-based solutions such as VirtualBox or VMWare, server based “Virtual Private Servers” such as Xen, or sandboxed Virtual Machines for programming languages such as Java.


A virtual machine


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