Early Systems
This lesson briefly discusses the history of memory in operating systems to provide some context to the chapter.
In the early days, building computer systems was easy. Why do you ask? Because users didn’t expect much. It is those darned users with their expectations of “ease of use”, “high performance”, “reliability”, etc., that really have led to all these headaches. Next time you meet one of those computer users, thank them for all the problems they have caused.
From the perspective of memory, early machines didn’t provide much of an abstraction to users. Basically, the physical memory of the machine looked something like what you see in the figure below:
The OS was a set of routines (a library, really) that sat in memory (starting at physical address 0 in this example), and there would be one running program (a process) that currently sat in physical memory (starting at physical address 64k in this example) and used the rest of memory. There were few illusions here, and the user didn’t expect much from the OS. Life was surely easy for OS developers in those days, wasn’t it?
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