A virtual machine is a program on a computer that works just like it is a separate computer. The program that controls virtual machines is called a Hypervisor and the computer that is running the virtual machine is called the host. The hypervisor controls how the virtual machine can access memory, hard drive space, and other resources on the host computer. Virtual machines can be created through software known as virtualization software (such as VMware Workstation and VirtualBox).
There are many reasons to run a virtual machine.
- It is a (relatively) simple way of safely running multiple operating systems on one computer.
- A very powerful server can be split into several smaller virtual machines to use its resources better.
- It can help with security. If the virtual machine is affected by a virus, the host operating system is unaffected.
- Virtual machines that are fully emulated, such as Java, allow a program to run on many different types of computer without having to be recompiled.