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Modern Operating Systems by Herbert Bos and Andrew S. Tanenb...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf
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Modern Operating Systems by Herbert Bos and Andrew...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf-M ODERN O PERATING S YSTEMS
Modern Operating Systems by Herbert...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf-M ODERN O PERATING S YSTEMS
Page 113
82
INTRODUCTION
CHAP. 1
12.
Which of the following instructions should be allowed only in kernel mode?
(a) Disable all interrupts.
(b) Read the time-of-day clock.
(c) Set the time-of-day clock.
(d) Change the memory map.
13.
Consider a system that has two CPUs, each CPU having two threads (hyperthreading).
Suppose three programs,
P0
,
P1
, and
P2
, are started with run times of 5, 10 and 20
msec, respectively. How long will it take to complete the execution of these programs?
Assume that all three programs are 100% CPU bound, do not block during execution,
and do not change CPUs once assigned.
14.
A computer has a pipeline with four stages. Each stage takes the same time to do its
work, namely, 1 nsec. How many instructions per second can this machine execute?
15.
Consider a computer system that has cache memory, main memory (RAM) and disk,
and an operating system that uses virtual memory. It takes 1 nsec to access a word
from the cache, 10 nsec to access a word from the RAM, and 10 ms to access a word
from the disk. If the cache hit rate is 95% and main memory hit rate (after a cache
miss) is 99%, what is the average time to access a word?
16.
When a user program makes a system call to read or write a disk file, it provides an
indication of which file it wants, a pointer to the data buffer, and the count. Control is
then transferred to the operating system, which calls the appropriate driver. Suppose
that the driver starts the disk and terminates until an interrupt occurs.
In the case of
reading from the disk, obviously the caller will have to be blocked (because there are
no data for it).
What about the case of writing to the disk?
Need the caller be blocked
awaiting completion of the disk transfer?
17.
What is a trap instruction? Explain its use in operating systems.
18.
Why is the process table needed in a timesharing system?
Is it also needed in personal
computer systems running UNIX or Windows with a single user?
19.
Is there any reason why you might want to mount a file system on a nonempty direc-
tory? If so, what is it?
20.
For each of the following system calls, give a condition that causes it to fail:
fork
,
exec
,
and
unlink
.
21.
What type of multiplexing (time, space, or both) can be used for sharing the following
resources: CPU, memory, disk, network card, printer, keyboard, and display?
22.
Can the
count = write(fd, buffer, nbytes);
call return any value in
count
other than
nbytes
?
If so, why?
23.
A file whose file descriptor is
fd
contains the following sequence of bytes: 3, 1, 4, 1, 5,
9, 2, 6, 5, 3, 5.
The following system calls are made:
lseek(fd, 3, SEEK
SET);
read(fd, &buffer, 4);
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