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:
“Any memory for the most part depending on chance.”
—Philip Larkin (1922–1986)
“Freedom of religion, freedom of the press, and freedom of person under the protection of habeas corpus, and trial by juries impartially selected. These principles form the bright constellation which has gone before us, and guided our steps through an age of revolution and reformation.”
—Thomas Jefferson (1743–1826)