Adding memory (RAM) is one of the most common upgrades made to a computer. Many people think that this will speed up a computer. Adding memory to a computer can slightly improve its performance if the computer didn’t previously have sufficient memory installed to accommodate the applications running simultaneously. Let me elaborate to add some clarifying detail. [Update 2015: Many Macintosh model now have their memory soldered in place so additional memory can’t be added in the future. Thus, it’s important to equip new Macs with enough memory when you purchase them.]

A computer’s processor (CPU) is a chip which carries out the instructions of an application. The faster the processor, the faster tasks can be completed. Currently, common processor chips are the Core Duo, Core 2 Duo and Core i3, i5 and i7. These processors typically run at speeds around 2.0 to 3.0 Gigahertz (GHz). The speed of a computer’s processor is generally the largest factor in the computer’s performance. Typically, it’s not possible to either speed up or replace a processor in today’s desktop or laptop computers. Thus, people have to make other changes to improve a computer’s performance.

Applications such as Microsoft Word are permanently stored on the hard drive. When one opens Microsoft Word, large parts of it are copied into memory (RAM). As one opens more and more applications, one uses up all of the available memory in a computer. Eventually, the computer will start to use virtual memory. It’s beyond the scope of this article to explain virtual memory, but trust me when I indicate that it’s slower then regular memory.

If one were to add more memory to a computer, the computer would need to rely on virtual memory less when a lot of applications are open simultaneously. Consequently, the computer’s performance would be improved. It’s common to need to add memory to a computer a few years after it was purchased, especially if one has installed updated versions of applications like Word or the Mac operating system, Mac OS X. This is because new versions typically require more memory than their predecessors and thus utilize the computer’s memory faster, causing it to begin using virtual memory sooner.

Here are a few Wikipedia articles which could be useful if you want to dig deeper to try to understand some of the terms that I mentioned above: RAM (random access memory), CPU (central processing unit), GHz (gigahertz), virtual memory.