Memory Protection
When multiple programs are present in memory, an ill-behaved program may (inadvertently or deliberately) overwrite memory belonging to another program, or even to the operating system itself.
The operating system therefore restricts the memory accessible to the running program. A program trying to access memory outside its allowed range is immediately stopped before it can change memory belonging to another process.
Another key innovation was the idea of privilege levels. Low privilege tasks are not allowed some kinds of memory access and are not allowed to perform certain instructions. When a task tries to perform a privileged operation a trap occurs and a supervisory program running at a higher level is allowed to decide how to respond.
Read more about this topic: Computer Multitasking
Famous quotes containing the words memory and/or protection:
“Our memory is like a shop in the window of which is exposed now one, now another photograph of the same person. And as a rule the most recent exhibit remains for some time the only one to be seen.”
—Marcel Proust (1871–1922)
“We’re for statehood. We want statehood because statehood means the protection of our farms and our fences; and it means schools for our children; and it means progress for the future.”
—Willis Goldbeck (1900–1979)