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:
“There are no stars to-night
But those of memory.
Yet how much room for memory there is
In the loose girdle of soft rain.”
—Hart Crane (1899–1932)
“The diversity in the faculties of men, from which the rights of property originate, is not less an insuperable obstacle to a uniformity of interests. The protection of these faculties is the first object of government.”
—James Madison (1751–1836)