Page 13 - slides.dvi

•
•
•
•
–
–
2.
1.
Operating
But:
First
Hence
Some
Systems
Accesses
try:
—
Protecting
need
Application
to
applications
applications
make
devices
Structures
outside
I/O
&
can
I/O
can’t
can’t
&
protect
Protection
allowed
accessed
rewrite
mask
control
via
memory
range
Mechanisms
0x0000
0x3000
0x5000
0xD800
instructions
0xFFFF
0x9800
Memory
I/O
are
interrupt
also,
interrupts.
memory
e.g.
devices.
System
Job 1
Job 4
Job 3
Job 2
privileged.
Operating
vectors.
protected.
define
base
0x5000
0x4800
base register
limit register
and
limit
for
each

program:

9