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)
“Men speak of natural rights, but I challenge any one to show where in nature any rights existed or were recognized until there was established for their declaration and protection a duly promulgated body of corresponding laws.”
—Calvin Coolidge (1872–1933)