The earliest form of computer displays were large cathode-ray tubes. Because of the size of the displays, computer systems were comprised of three key components: the monitor, the computer case, and the input devices. As the size of the monitors decreased, computer companies started to integrate the computer case into the monitor to create an all-in-one. These first all-in-one computer systems were still quite large and generally cost a fair amount compared to a standard computer setup. Read More from Life Wire