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How Virtual Machines Work

written by: Jeremy Bost•edited by: Michele McDonough•updated: 5/6/2010

What are system virtual machines, and how might they interest you? Well, in short, they are "computers/operating systems running inside other computers." This is explained below.

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    In software reviews, often a program is tested in a platform virtual machine. If you are a programmer, you may use virtual machines to see if your product runs safely in another operating system—for example, the different versions of Windows. Maybe you like to test and analyze malware, and don't want to get your computer infected. This virtualization can help.

    So what are virtual machines, and what do they do?

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    Table of Contents

    • What Are Virtual Machines - What is all the fuss about?
    • How Can You Use Virtualization? - You want to try it, too?
    • Limitations - Some may have second thoughts.
    • Conclusion - The usual conclusion: It may work for you, or it may not.
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    What Are Virtual Machines?

    Hardware, server, or platform virtualization is the technology of running a virtual operating system inside of another operating system. Basically, you now have two computers going. (If you don't already know, operating systems are what "run" your computer. Without them, you couldn't do much. OSes help you execute and use programs you want. If you don't know what an operating system is, you are probably running some version of Windows.)

    Things on a virtual machine have almost no way to access your real computer, unless you configure it too. So, if a virus infects your virtual computer and now it shows pop-ups every 5 seconds, you can just "delete" it and make a new one.

    This creates quite a few possibilities. Some are mentioned above, but here is another one (after all, examples can help you realize when something is the best). You see this great-looking, free program. The thing is, you aren't sure if it is trustworthy, and/or if it will fit your needs. Pull up your virtual machine, and try this program just like you would on a "real" computer. With some virtual machine hosters, you can restore your machine to another state you had been in at a previous time. This allows you to quickly delete or go back to another state if you dislike whatever you tried.

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    How Can You Use Virtualization?

    Yes, you can use it virtualization too. Some virtualizer programs are free, while others cost quite a bit. A comparison by another Bright Hub writer is done here in a 3-part series: VMware Vs VirtualBox Vs Virtual PC 2007. There are also the separate reviews for each of these:

    1. The free Sun VirtualBox.
    2. The free Virtual PC 2007.
    3. The free VMware Player, or the paid VMware Workstation. Workstation has more features (and it happens to be what I use).

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    If you are thinking this is going to eliminate the need for a better computer to run more programs at the same time, etc.— I'm afraid you need to think again. Virtual machines use the same memory, the same CPU, and same hard drive as your real, host computer. This can be quite a problem, especially for computers with low specs.

    For example: On my laptop, I have 2GB of memory. Usually, that is quite enough to satisfy me, as often I only use about 50-55% of it. However, running two operating systems, one on a virtual machine, can increase that to 90+%. With that amount of RAM used, memory swapping might occur, and that slows things down.

    So just remember: If you don't have a new, high-end computer, virtual machines can make things a bit slower. For me, most of the time running one is something of an ordeal, because I have to shut down mostly unnecessary processes and services.

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    A virtual machine has many uses—security, trialing, studying. But it also sucks up system resources, so it isn't an easy thing for some.

    If you have any questions, comments, or suggestions, please leave a comment. Often it will be approved and answered in less than 24 hours.