Let's say you bought your PC two years ago, but now want to add a scanner. In an IBM you must plug in a scanner expansion card into an empty expansion slot in your PC. Your PC will now be able to talk to the scanner.

Expansion slots come in several different sizes. An 8-bit expansion slot is smaller than a 16-bit expansion slot. A 32-bit expansion slot is bigger still. The important thing to remember is to match expansion cards with the right expansion slot.

There are many expansion cards on the market today. Just remember that each function on your PC generally requires some type of expansion card.

Many such expansion cards are already built in, or present in the Mac.