History, as we know, began on January 1, 1970. I'll roughly characterize the seventies as the era of the mainframe -- one big chunk of iron, with CPU (gears) and disk resources shared by many users, likely in many departments. This gave the system a single-system image, in the sense that no matter which terminal you sat in front of, or ``where'' in the system your programs ran, you saw a uniform view of the resources in the system.