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:
“I don’t avoid pain by not remembering something; I try to remember.... Memory is empowering, and it’s what gives you your sense of continuity in the world.”
—Melinda Worth Popham (b. 1944)
“A strong egoism is a protection against disease, but in the last resort we must begin to love in order that we may not fall ill, and must fall ill if, in consequence of frustration, we cannot love.”
—Sigmund Freud (1856–1939)