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TEST BANK FOR
OPERATING SYSTEM
CONCEPTS, 8 TH
EDITION: ISBN:
3 BY GREG GAGNE
CHAPTER 1
EXERCISES
UPDATED A+
IDENTIFY WHICH OF THE FUNCTIONALITIES
LISTED
BELOW NEED TO BE SUPPORTED BY THE
OPERATING SYSTEM FOR (A) HANDHELD
DEVICES AND (B) REALTIME SYSTEMS.
A. BATCH PROGRAMMING
B. VIRTUAL MEMORY
OPERATING SYSTEM? - CORRECT
ANSWER-1.
MAKE IT EASIER FOR USERS TO INTERACT
WITH THE COMPUTER 2.
CONTROL THE EXECUTION OF
APPLICATION SOFTWARE
3. MANAGE SYSTEM RESOURCES
WHAT ARE THE MAIN DIFFERENCES
BETWEEN
OPERATING SYSTEMS FOR MAINFRAME
COMPUTERS
AND PERSONAL COMPUTERS? - CORRECT
ANSWER-MAINFRAME COMPUTERS CAN
RUN VARIOUS OPERATING SYSTEMS
PERSONAL COMPUTERS CAN ONLY RUN ONE
OPERATING SYSTEM AT A TIME
WE HAVE STRESSED THE NEED FOR AN
OPERATING
SYSTEM TO MAKE EFFICIENT USE OF THE
COMPUTING HARDWARE. WHEN IS IT
APPROPRIATE
FOR THE OPERATING SYSTEM TO FORSAKE
THIS
PRINCIPLE AND TO "WASTE" RESOURCES?
WHY IS
SUCH A SYSTEM NOT REALLY WASTEFUL? -
CORRECT ANSWER-IT IS APPROPRIATE
TO
"WASTE" RESOURCES IF IT MEANS THAT THE
USER
GETS BETTER INTERACTION WITH THE
MEMORY 3. LOAD STARTING
ADDRESS AND BEGIN EXECUTION
4. MONITOR AND CONTROL EXECUTION OF
PROGRAM FROM CONSOLE
WHAT IS THE MAIN DIFFICULTY THAT A
PROGRAMMER MUST OVERCOME IN WRITING
AN
OPERATING SYSTEM FOR A REAL-TIME
ENVIRONMENT? - CORRECT
ANSWERTHE MAIN
DIFFICULTY IS KEEPING THE OPERATING
SYSTEM
WITHIN THE FIXED TIME CONSTRAINTS OF A
REALTIME SYSTEM. IF THE SYSTEM DOES
NOT COMPLETE
A TASK IN A CERTAIN TIME FRAME, IT MAY
CAUSE A BREAKDOWN OF THE ENTIRE
SYSTEM IT IS RUNNING.
THEREFORE WHEN WRITING AN OPERATING
SYSTEM
FOR A REAL-TIME SYSTEM, THE WRITER
MUST
BE SURE THAT HIS SCHEDULING
SCHEMES DON'T ALLOW RESPONSE TIME
TO EXCEED THE TIME CONSTRAINT.
CONSIDER THE VARIOUS DEFINITIONS OF
OPERATING SYSTEM. CONSIDER WHETHER
THE OPERATING SYSTEM SHOULD INCLUDE
APPLICATIONS SUCH AS WEB BROWSERS
AND MAIL PROGRAMS.
ARGUE BOTH THAT IT SHOULD AND THAT IT
SHOULD
(SECURITY) SYSTEM? - CORRECT
ANSWER-ANSWER:THE
DISTINCTION BETWEEN KERNEL MODE AND
USER
MODE PROVIDES A RUDIMENTARY FORM OF
PROTECTION IN THE FOLLOWING MANNER.
CERTAIN
INSTRUCTIONS CAN BE EXECUTED ONLY
WHEN THE
CPU IS IN KERNEL MODE. SIMILARLY,
HARD-
WARE DEVICES COULD BE ACCESSED ONLY
WHEN THE PROGRAM IS EXECUTING IN
KERNEL MODE.
CONTROL OVER WHEN INTERRUPTS COULD
BE ENABLED OR DISABLED IS ALSO
POSSIBLE ONLY WHEN THE CPU IS IN
KERNEL MODE.
CONSEQUENTLY, THE CPU HAS VERY
LIMITED
SOME EARLY COMPUTERS PROTECTED THE
OPERATING SYSTEM BY PLACING IT IN A
MEMORY
PARTITION THAT COULD NOT BE MODIFIED BY
EITHER THE USER JOB OR THE OPERATING
SYSTEM
ITSELF. DESCRIBE TWO DIFFICULTIES THAT
YOU
THINK COULD ARISE WITH SUCH A SCHEME. -
CORRECT ANSWER-THE DATA
REQUIRED
BY THE
OPERATING SYSTEM (PASSWORDS, ACCESS
CONTROLS, ACCOUNTING INFORMATION,
AND
SO ON) WOULD HAVE TO BE STORED IN OR
PASSED
THROUGH UNPROTECTED MEMORY AND
THUS BE ACCESSIBLE TO UNAUTHORIZED
USERS
SOME CPUS PROVIDE FOR MORE THAN TWO
MODES OF OPERATION. WHAT ARE TWO
POSSIBLE
USES OF THESE MULTIPLE MODES? -
CORRECT
ANSWER-MULTIPLE MODES COULD BE
USED TO
PROVIDE A FINER-GRAINED SECURITY
POLICY. FOR
EXAMPLE, RATHER THAN DISTINGUISHING
BETWEEN
JUST USER AND KERNEL MODE, YOU COULD
ALLOW USB DEVICE DRIVERS TO RUN. THIS
WOULD
MEAN THAT USB DEVICES COULD BE
SERVICED
WITHOUT HAVING TO SWITCH TO KERNEL
MODE,
THEREBY ESSENTIALLY ALLOWING USB
DEVICE
DRIVERS TO RUN IN A QUASI-USER/KERNEL
MODE
TIMERS COULD BE USED TO COMPUTE THE
CURRENT
TIME. PROVIDE A SHORT DESCRIPTION OF
HOW THIS
COULD BE ACCOMPLISHED. - CORRECT
ANSWER-
A PROGRAM COULD USE THE FOLLOWING
APPROACH TO COMPUTE THE CURRENT TIME
USING
TIMER INTERRUPTS. THE PROGRAM COULD
SET A
TIMER FOR SOMETIME IN THE FUTURE AND
GO TO
SLEEP. WHEN IT IS AWAKENED BY THE
INTERRUPT,
IT COULD UPDATE ITS LOCAL STATE, WHICH
IT
IS
USING TO KEEP TRACK OF THE NUMBER OF
INTERRUPTS IT HAS RECEIVED THUS FAR. IT
COULD
THEN REPEAT THIS PROCESS OF
CONTINUALLY
G. SWITCH FROM USER TO KERNEL MODE.
H. ACCESS I/O DEVICE. - CORRECT
ANSWER-A. SET VALUE OF TIMER
C. CLEAR MEMORY
E. TURN OFF INTERRUPTS
F. MODIFY ENTRIES IN DEVICE-STATUS TABLE
H. ACCESS I/O DEVICE
THE REST CAN BE PERFORMED IN USER
MODE
IS THE INTERNET A LAN OR A WAN? -
CORRECT
ANSWER-THE INTERNET IS A TYPE OF
WAN
BECAUSE IT COVERS THE ENTIRE GLOBE
IN A MULTI-PROGRAMMING AND TIME-
SHARING
ENVIRONMENT, SEVERAL USERS SHARE THE
SYSTEM SIMULTANEOUSLY. THIS SITUATION
CAN RESULT IN VARIOUS SECURITY
PROBLEMS.
A. WHAT ARE TWO SUCH PROBLEMS?
B. CAN WE ENSURE THE SAME DEGREE OF
SECURITY IN A TIME-SHARED MACHINE AS
IN A DEDICATED
MACHINE? EXPLAIN YOUR ANSWER. -
