CSE 430/598
FALL 99
MIDTERM 1
NAME
(25) 1. (7) (a) Place a P in the space next to each of the following instructions if it should be
privileged and an NP if the instruction need not be privileged.
turn off interrupts
turn on timer interrupts
switch from kernel to user mode
switch from user to kernel mode
write to kernel memory
read value of the timer
divide contents of two registers and
place quotient in a third register
(18) (b) For each instruction in part (a) that you said should be privileged, give one reason why
the instruction should be privileged. Note: your answer needs to be specific. For example,
simply saying that the operating system will be protected will not do. You need to say why or
how.
