Do you remember talk of the “Super computer”? These were massive servers with names like Cray, Wang, etc. They were expensive, and scarce. So scarce in fact that engineers had to figure out a way to run multiple programs which shared the computers internal resources on one machine. How did they do it? They separated the application (like today’s Microsoft Outlook, Oracle databases,etc) and the Operating System (Windows, Linux, Unix). They converted each into a file which shared the computing resources of the supercomputer all at the same time. Voila, Virtualization!