ABSTRACT
Powerful digital systems have changed lives in significant ways. In general, the easier it is to control any given system through its interface, the better. Computer user interfaces (UIs) have evolved quite quickly. Later, the keyboard and cathode-ray tube (CRT) display combined to provide a command line interface (CLI) where a user entered commands interactivity and received results immediately on the CRT. At an interface, one system, a user for example, is usually the client and the other, an application (app) for example, is the server. The operating system (OS) is central to a computer. It interfaces with software, hardware, and users. Animals use eyes, ears, nose, and skin to interface and interact with the environment. Human beings are independent systems. They interface with one another easily and constantly. Today, human interfacing has become even more instant and convenient because of phone calls, email, texting, online chat, and social media.
