12.3.4.3 explain the concept of virtual machine 

Virtual machine

Virtual machine is a software application run by the host operating system of a computer that simulates a stand-alone computer system.

Very often, a programmer or IT engineer working in an operating system needs to simulate the operation of another operating system. For example, you are working on a computer running a Windows operating system, and you want to test the operation of a program under the Linux operating system. Of course, you can install a second operating system on your computer, but this requires certain qualifications and, if mistaken, can lead to the failure of the main operating system. It is safer to install a virtual machine. You will be able to get the operating system as if inside another operating system.

The program for creating and managing a virtual machine on a host computer is called a hypervisor or Virtual Machine Manager (VMM). The hypervisor assigns the necessary physical system resources (CPU, RAM, and hard disk) to each virtual machine. This prevents conflicts from occurring between different virtual machines.

The most important thing is that there can be as many such child operating systems. Their number is limited only by the resources of your computer.

There may be several reasons for using a virtual machine on your computer:

• Testing an additional operating system
• Testing various programs
• Launching potentially dangerous programs
• Running programs incompatible with the operating system installed on your computer

Advantages

• Less electricity used - you use one computer instead of two
• You can quickly switch between operating systems
• Cheaper, you don't need to buy a new computer
• You can store the entire "computer" in one file

Disadvantages

• Makes your computer slower by starting two systems at the same time
• If the main operating system crashes, you will lose other operating systems as well
• There may be compatibility issues

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Ex. 1

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