CSE 430
FALL 2007 MIDTERM 1
(3:15 CLASS)
NAME
Put Name on Every Page
1. (12) Introduction to operating systems
Early in Chapter 1, SG&G say: “An operating system is similar to a government.”
(a) (6) In general, what is it that an operating system provides that makes it like a government?
Give an example.
(b) (6) What negative characteristic do SG&G say an operating system has in common with a
government? Give an example of this and state why it is relevant.
2. (10) Hardware Protection
(a) (5) In order to make sure an operating system will perform correctly, modern computers
provide dual mode operation, e.g., user and kernel modes, and define certain instructions such as
halt and I/O instructions as 'privileged', that is, only allowed when the computer is in kernel
mode. Why do operating systems that make use of these features provide system calls
implemented by trap instructions?
(b) (5) I/O is often “memory mapped”, i.e., done with loads and stores to and from control and
status registers and data buffers. Given that ordinary loads and stores are not privileged
instructions, explain how operating systems protect memory mapped I/O, i.e., how ordinary
users are prevented from performing memory mapped I/O.
