What is virtual memory?

  • Virtual Memory is a integral part of every Operating System.
  • You may have many times heard this term tossed by computer geeks.
  • This post will clear all your doubts on What is virtual memory and how it is necessary this days.
  • As  every one wants to do multiple tasks at one time, as human nature is.
  • So What would happen if you would have opened like say image editor, word processor and media player all three applications on a Windows operating system simultaneously, with RAM around for EX: 64MB to 128 MB on a computer??? (Though today computers have much more then 64 Mb or 128 Mb of RAM)
  • If there were no such thing as virtual memory, your computer would have to say, “Sorry, you cannot load any more applications. Often it happens with certain applications or software RAM is not enough to run them. 
  • Your computer would surely crash or would not respond as you expected. Also it would say please close one application!
  • But with Virtual memory  the computer can look for areas of RAM that have not been used recently and copy them onto the hard disk. 
  • so this frees up space in RAM to load the new application. The application or process that is in current use is only loaded in RAM. You won’t even know when all this happening as it happens automatically  Because of  Virtual Memory  computer feels like is has unlimited RAM space even though it has only 32 megabytes installed. 
  • Moreover hard-disks are cheaper than RAM chips, virtual memory also provides a nice economic benefit.
  • So this concludes that due to Virtual Memory only those program that are in currently used or processed are stored in RAM, and all other process though open but inactive are stored in hard disc.
  • And whenever this inactive processes become active RAM retrieves them back from hard disc.
  • The area where this swapping is done in hard disc are known as pages or page files.
  • This area holds pages of RAM in hard disc, and the operating system moves data back and forth between the page file and RAM. (On a Windows machine, page files have a .SWP extension.)
  • But the read/write speed of a hard drive is much slower than RAM, and the technology of a hard drive is not geared toward accessing small pieces of data at a time.
  • If your computer has to depend on virtual memory. you will notice a performance drop or slow response.
  • So if you are looking to buy new pc look for  enough RAM so that you can work on many applicaitons simultaneously. 
  • Then, the only time you “feel” the slowness of virtual memory is in the slight pause that occurs when you change tasks. 
  • If you have enough RAM for your needs, virtual memory works beautifully. And if you have less RAM operating system has to constantly swap information back and forth between RAM and the hard disk. This will make you feel that your computer is slow.
  • This is also called thrashing.

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