The Desktop Computer
Desktop computers are meant to be used at a desk or table. They are different from mainframe computers, which can take up a whole room, and laptops, which are meant to be carried from one location to another. Initially, a desktop computer was just a smaller version of a mainframe, but today, they are at the larger end of the size spectrum because today's computers are growing ever smaller.
The first desktop computers were specifically laid out, and they had most of their components such as the hard drive, CPU, and RAM within a case that sat upright on a desktop. The monitor sat on top of the case, and the peripherals attached to the case.
In later years, the tower took over the world of the desktop computer. These cases sit vertically and they are either put under a desk or next to the monitor rather than underneath it. Tower desktop PCs have more space for media or hard drives or other equipment. The desktop computer has enjoyed varying degrees of popularity over the years. Most of Apple's first computers were all-in-one, and the monitor was part of the case. Their iMac series continued that tradition. All-in-one desktop computers have a few advantages over their counterparts; they are more portable, they are more attractive, and they take up less space on the desk.
However, all-in-one computers are harder to upgrade than regular desktops, because their parts are carefully fit into the case and sometimes soldered to other parts. The desktop has been more popular than the laptop for a few reasons. Since parts are larger, desktops are usually less expensive than laptops, but the gap has narrowed over the past few years. Desktop computers are able to have higher-powered components than similarly-aged laptops, making them better suited to tasks such as sound/video editing, gaming and graphic design.
In most cases, desktop PCs at their peak are about 18 months ahead of a similar laptop. Desktops are easier to customize than laptops because parts aren't so carefully fit, so most that like to build or modify their computers prefer the desktop over a laptop.