Page 12 - slides.dvi

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2.
1.
Operating
Make
Want
User
provide
Systems
to
Kernel
Hardware
—
operation:
Dual-Mode
certain
stop
Mode
:
Mode
Structures
:
hardware
&
contains
buggy
a
when
machine
when
(or
Protection
support
Operation
reset
to
mode-bit,
executing
Mechanisms
executing
instructions
on
malicious)
e.g.
Mode
Kernel
on
0
only
distinguish
behalf
behalf
program
means
of
a
of
possible
between
from
set user mode
interrupt or fault
the
in
user
kernel,
(at
1
doing
User
(i.e.
Mode
kernel
least)
bad
operating
means
two
mode.
.
user.
.
things.
application
system.
different
programs).
modes
8
of