4th
the essential move that made computers: storing instructing
“At first glance, the notion of storing instruction in a computer didn’t seem particularly clever, but it flies in the face of mechanical tradition. Machines have always been controlled from the outside; you turned some switches and the gadgets did your bidding. Even if the devices were contolled by punched tape or cards, like the jacquard loom or the analytical engine, the best modus operandi seemed to be the stash of the cards outside the machineand insert them when you needed them. Indeed, you couldn’t very weel hope to do more, since the practical shortcomings of gears and axles made it difficult if not impossible to build a large memory—although relays made the job much easier. As a result, no one, with the possible exception of Zuse, concieved of the stored program before the invention of ENIAC. (Stan Augarten, Bit by Bit, 134)
