A desktop computer is a personal computer (PC) in a form intended for regular use at a single location, as opposed to a mobile laptop or portable computer. Early desktop computer designs lie flat on the desk, while modern towers stand upright. Most modern desktop computers have separate screens and keyboards.
Early personal computers, like the IBM PC, were “desktop” machines, with a horizontally oriented computer case, usually intended to have the display screen placed on top to save space on the desktop. In modern usage the word “desktop” usually refers to tower cases that are in fact more often on the floor under the desk than on a desk.
Technically speaking desktop and tower computers are two different styles of computer case that use desk space in varying ways. Early computers took up the space of a room. Minicomputers generally fit into one or a few refrigerator sized racks. It was not until the 1970s when computers such as the HP 9800 series desktop computers were fully programmable computers that fit entirely on top of a desk. More desktop computer models introduced in 1971, lead to a model programmable in BASIC in 1972. They used a smaller version of a minicomputer design based on read-only memory (ROM) and had small one-line LED alphanumeric displays. They could draw computer graphics with a plotter. The Wang 2200 of 1973 led operating systems such as Mac (Macintosh) and Windows.