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:
“The advantage of having a bad memory is that you can enjoy the same good things for the first time several times.”
—Friedrich Nietzsche (1844–1900)
“If one really wishes to know how justice is administered in a country, one does not question the policemen, the lawyers, the judges, or the protected members of the middle class. One goes to the unprotected—those, precisely, who need the laws’s protection most!—and listens to their testimony.”
—James Baldwin (1924–1987)