How Do Universal Turing Machines Differ from the ENIAC?
The previous explanation spelled out the differences between a digital computer and an analog computer. But what is the unique characteristic of a digital computer? The Stanford Encyclopedia of Philosophy’s The Modern History of Computing describes the programming of a universal Turing machine as the manipulation of symbols stored in readable and writable memory: In 1936, at Cambridge University, Turing invented the principle of the modern computer. He described an abstract digital computing machine consisting of a limitless memory and a scanner that moves back and forth through the memory, symbol by symbol, reading what it finds and writing further symbols (Turing [1936]). The actions of the scanner are dictated by a program of instructions that is stored in the memory in the form of symbols. This is Turing’s stored-program concept, and implicit in it is the possibility of the machine operating on and modifying its own program. The ENIAC was manipulating current and voltages to perfor
