What is Virtual Memory?

Over the holiday break I was reading through reader feedback and found a great question: What is "Virtual Memory?" I know there's a great joke in that question somewhere but I can’t remember what it is...

Anyway, when you're talking about your computer, virtual memory refers to a technique the operating system uses to help it work with your applications and files. The Microsoft Computer Dictionary definition is: "Memory that appears to an application to be larger and more uniform than it is. Virtual memory can be partially simulated by secondary storage such as a hard disk."

OK, so what does that mean? To understand virtual memory, you first need to understand the hardware your computer uses to store information.

First, there's the hard drive, where your software and data files are stored permanently. Your hard drive looks a bit like this:

Hard drive

Second, there are memory chips, which are used to temporarily store the software and information (such as documents and pictures) your computer is actively working with. Memory chips look like this:

Memory chip

You also store information on removable media, such as CDs and USB drives, but this discussion is confined to the storage that stays in your computer.

You'll often hear the memory chips in your computer referred to as RAM, which is short for Random Access Memory (which means pretty much just that, memory that's used in a random, rather than sequential, manner). The more RAM your computer has, the more software and files it can juggle at the same time without having to read or write stuff onto or off of your hard drive. This is why computers with more RAM tend to run faster than those with less.

Regardless of how many RAM chips you've got in your computer, virtual memory helps increase your computer's performance by using hard drive space as a way to extend the storage area available to RAM. Also called disk memory, this process uses something called a page file to move information in and out of the RAM chips on your computer.

Virtual memory uses page files to move information between your hard drive and RAM

Generally, you shouldn't run into trouble with the virtual memory functionality on your computer. If you get an error message referring to virtual memory, you can search for potential causes on https://support.microsoft.com, or contact your technical support resource.

I'll close with a trivia note: In researching this topic, I saw virtual memory referred to as one of the under-acknowledged computing breakthroughs of the 20th century. It was first used in mainframe computers in the 1960s.

—Robbin Young