“One consequence of this principle of universality is that the only important difference in power between two computers is their speed and the size of their memory. Computers may differ in the kinds of input and output devices connected to them, but these so-called peripherals are not essential characteristics of a computer, any more than its size or its cost or the color of its case. In terms of what they are able to do, all computers (and all other types of universal computing devices) are fundamentally identical.”