Within the next few years, we will see an exponential growth in micro touch screen devices that can be unfolded from 3x6 to 12x6 (and other sizes) to form a touch screen. These devices will have no hard drive, no CD/DVD, no memory other than an ultra-thin EPROM, and no external ports.
This is an example virtual water flow circuit used to illustrate how a computer circuit can be configured using the natural flow of electrons using water as an example. It is used in part 3 of a 4 part series of "How A Computer Works". Each Dam can be configured to release water flow at certain pressures and directions.