Retailers are very often limited for space, and their point-of-sale equipment therefore needs to be as compact as possible.
An integrated POS system is ideal in these circumstances. It is a compact unit which normally houses its hard drive and processor in the base of the monitor, and so takes up a very small footprint.
Some units come with an optional integration tray which combines the cash drawer, docket printer and keyboard into a single unit, and which limits the number of unsightly wires. Alternatively, you may choose to attach your cash drawer under the counter, using optional mounting brackets.
A POS system is usually used purely for point-of-sale, and as such does not require much processing power. For this reason many are configured with a 1.2ghz or even lower processor. They are not designed to act as a PC, and do not normally have a CD-rom or floppy disk drive. Operating Systems and software and are normally loaded at installation, over a network, or using an external CD-rom drive.