“Naming the two signals in computer logic 0 and 1 is an example of functional abstraction. It lets us manipulate information without worrying about the details of its underlying representation. Once we figure out how to accomplish a given function, we can put the mechanism inside a “black box,” or a “building block” and stop thinking about it. The function embodied by the building block can be used over and over, without reference to the details of what’s inside. This process of functional abstraction is a fundamental in computer design—not the only way to design complicated systems but the most common way”