They've got the right idea. With modern computers, memory isn't that big of a deal. In the past, you had to worry about all sorts of different kinds of memory with odd names and obscure functions. Now you can be safe in dealing with memory. Just go to the store, hand over your plastic, and take home all the memory you need.

Well, it's not quite that easy. What you don't know about memory can be a big handicap and can lead to your buying a handful of unusable chips and even a computer that no longer works.

Moreover, if you have too little memory installed in your computer, there may be no overt symptoms—except your computer runs a lot more slowly than it could. You'll never see a warning that says, "Slowdown ahead. Add more megabytes." Windows and your programs leave you on your own to guess whether you have enough or too little or too much.

Modern computers make adding memory as easy as sliding a small card called a memory module into a slot. Usually you have nothing more to adjust. You system comes to life with more memory and greater capabilities—if it comes to life again at all.

Adding the wrong kind of memory can, in fact, stop it from booting up. Even the relatively benign mistake of adding memory with too low of a rated speed can compromise your system's performance. A fast computer can lose a big fraction of its performance when you slide in a module with the wrong rating.

Dig a bit deeper into your computer, and you'll discover that there's a lot more to memory than just quantity, however. Memory is storage, certainly, but it is also a portal into your display. Your computer's operating system slices and dices it to suit its needs, storing vital data here and there and stealing blocks of memory addresses for the interfaces it uses.

Memory is more than modules, too, because the same stuff (or at least a close cousin) of the stuff that makes your programs run also has become a convenient secondary storage medium for applications "on the go." Solid-state memory makes digital cameras and MP3 workable and convenient. Without it, you'd need a handful of floppy disks for every song you want to play or picture you've taken.

We'll start our tour of electronic storage technology with a practical look at how much memory you need, why you come up short even when you have enough, and how much is enough.

From there, we'll look at the technologies involved in different memory types so you can understand the differences in the kinds of memory available—and the kind you might want to install to increase your system's memory capacity.

After an examination of memory modules—what your computer uses for its basic memory needs—we'll look at other memory packages: the cards, chips, and sticks that serve MP3 players and digital cameras as a mass storage and exchange medium.