What is virtual memory?

Virtual memory is an essential feature found in most operating systems on desktop computers. Its widespread use is due to its remarkable ability to offer significant benefits at a minimal cost to the user.

Today's computers typically come with around 64 or 128 megabytes of RAM (random-access memory), which is allocated for use by the CPU (central processing unit). However, this amount of RAM often isn't enough to run all the programs that users want to operate simultaneously. For instance, loading the Windows operating system, an e-mail client, a web browser, and a word processor may overwhelm 64 megabytes of RAM. Without virtual memory, your computer would prompt, "Sorry, you cannot load any more applications. Please close one to open another." Virtual memory allows the system to identify unused portions of RAM and transfer them to the hard disk, creating room for the new application. This process happens in the background without you noticing, giving the impression of infinite RAM space, even when only 32 megabytes are installed. Additionally, since hard drive space is far cheaper than RAM, virtual memory offers an economic advantage.

The space on the hard drive used to store the data from RAM is referred to as the page file. It stores RAM pages on the hard disk, with the operating system constantly moving data between the page file and RAM. (In a Windows environment, page files are typically saved with a .SWP file extension.)

It's important to note that the read/write speed of a hard drive is significantly slower than that of RAM, and hard drives are not optimized for handling small chunks of data. If your system over-relies on virtual memory, you may notice a substantial decrease in performance. The key to avoiding this is ensuring you have enough RAM to handle all your tasks at once. When there is enough RAM, you won’t perceive the effects of virtual memory, except for a brief pause when switching tasks. If you don't have enough RAM, however, the operating system will constantly transfer data between RAM and the hard disk, resulting in thrashing, which can drastically slow down your computer.

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