Smaller versions of the desktop PC are referred to as portable, transportable, palm tops, and luggable. These computers are typically not cost effective for smaller companies but can provide medium and larger companies with a powerful means of supporting large numbers of users through a single processing unit. Although mainframe computers are touted as dinosaurs today, they provide needed services to segments of the computing market that can afford them and require their computing power. Liken the CPU of a PC to your body. Your body is the shell that houses your brain, heart, eyes, and so forth.
Hard drives vary greatly in the amount of data they can store.
In the past, SCSI drives were much more dependable and faster than IDEs. The SCSI drives were also inherently more expensive. Although this is still the case, advancements in IDE technology have closed the gap in speed and size. I would still recommend using SCSI drives in your servers and IDE drives in the workstations or client machines. When asked how much hard drive space is required for database applications, I take the attitude that storage is inexpensive when compared with everything else.