 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| ä |
Memory
protection
|
|
|
|
ä |
do
not allow the memory area containing the
|
|
|
monitor
to be altered by user programs
|
|
|
| ä |
Timer
|
|
|
|
ä |
prevents
a job from monopolizing the system
|
|
|
|
ä |
an
interrupt occurs when time expires
|
|
|
| ä |
Privileged
instructions
|
|
|
|
ä |
can
be executed only by the monitor
|
|
|
|
ä |
an
interrupt occurs if a program tries these
|
|
|
instructions
|
|
|
| ä |
Interrupts
|
|
|
|
ä |
provides
flexibility for relinquishing control to
|
|
and
regaining control from user programs
|
|
|
| ä |
manage
resource contention
|
|
|
|
ä |
either
hardware support through special
|
|
|
instructions
(lock, swap, …)
|
|
|
|
ä |
software
support: semaphores, monitors, ….
|
|
