Understanding Virtual Memory

by Barry Dysert
(last updated October 19, 2015)

3

Virtual memory is the name given to the contiguous address range used by a computer program. For a program to run, its instructions must reside in physical memory. However, when there are several programs running simultaneously or when there's not enough physical memory to encompass the amount of memory needed by a program, the computer uses virtual memory to fulfill the program's needs.

For example, if two programs are running at the same time, each program treats memory as if it's one large contiguous block beginning at address zero and extending as far as necessary. Since each program can't access the memory at physical address zero simultaneously, the computer creates blocks (address ranges) of virtual memory that make it seem to each program that it has all of the computer's memory to itself.

Virtual memory is also used when programs need more memory than physically exists in the computer. The computer uses a process called paging to allow programs to access more memory than physically exists. Through paging, the computer keeps track of what blocks of physical memory are currently available, writes the contents of those blocks to disk, and then reads in from disk the previously written data that the currently executing program needs. By using the disk as a temporary storage medium, many different programs can be running at the same time and accessing large portions of memory without ever having to be concerned with whether the data is physically in memory at the time or needs to be paged in from disk.

 This tip (12623) applies to Windows 7 and 8.

Author Bio

Barry Dysert

Barry has been a computer professional for over 30 years, working in different positions such as technical team leader, project manager, and software developer.  He is currently a senior software engineer with an emphasis on developing custom applications under Microsoft Windows. ...

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What is eight minus 2?

2015-10-19 09:58:18

Henry Noble

Concur with Barry regarding the move to Win10.

From Win8.1, the leap to Win10 is small, and Win10 brings many desirable enhancements. The primary concern is with drivers and old programs. Do some online research on your system's peripherals to confirm that Win10 drivers are available. Also search online for the name of any old programs you are using to see if there is discussion about moving them to Win10.

For those with stable Win7 systems, sit tight until next summer.

Memory is not as much as an issue as you might expect with such a complex program because Win10 adapts to the environment in which it is installed. For example, Win10 works well on my dinky 8" tablet with 2 Gb of RAM.


2015-10-19 06:41:24

Barry

I can see moving to 10 if you're on 8.1 now. From what I understand, 10 still retains the ridiculous start *screen* that 8.* has. I'm on 7 at home and plan to stay on it until it becomes unsupported. Imo, 7 is the best OS that Microsoft has ever sold.

Since this tip is on virtual memory, has anyone moved to 10 and realized that you need more memory than you did for the previous version you were using?


2015-10-19 06:33:15

Ashley

I'm advising my friends and relatives to hold off any move to Windows 10 until at least the significant update, expected in early November. I'm also saying that if they are really happy with their current operating system (especially Windows 7 users), consider delaying even further until the signs are that the majority of known bugs/problems have been sorted out, afterall, they could wait until late July 2016 to upgrade and still obtain Windows 10 free.


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