342 EXAM

Question 1

How does a system service an interrupt and ensure the current instruction set is not upset?

Answer 1

Stabilize the system, save data, CPU reloads. (CPU: Disable all lesser-priority interrupts, save PC data to main memory, execute code from main memory.) Signals sent to the CPU to stop current activity and do something else.

Question 2

How are multiple interrupts handled?

Answer 2

Stabilize the system, save data, CPU reloads.

Question 3

Name three objects of an Operating System and explain in detail one of them.

Answer 3

Process management, Main memory Management, Input/output management, File Storage Management, kernel: It is the primary interface between the hardware and the processes of a computer. The kernel connects these two in order to adjust resources as effectively as possible. The kernel has the functions of memory management, process and task management, disk management, and CPU scheduling. The core of the operating system.

Question 4

What is the function of the Operating System?

Answer 4

The purpose of an operating system is to provide a platform on which a user can execute programs in a convenient and efficient manner.

Question 5

What does multiprogramming do for an Operating System?

Answer 5

Multiprogramming is the ability to run multiple jobs on a single system at the same time. Reduces CPU idle time.

Question 6

Why is there a memory hierarchy?

Answer 6

Because certain levels of storage are accessed much more than others at different levels, this allows for increased efficiency by minimizing access times.

Question 7

What are the major functions of the Operating System?

Answer 7

Makes list of authorized users
Make list of resources in system
List all processes running
Create processes
starts program execution
(Manages resources, provides abstractions)

Question 8

How does on OS architecture differ from another?

Answer 8

Monolithic architecture : In the monolithic systems, each component of the operating system is contained within the kernel.

Layered architecture : This is an important architecture of operating system which is meant to overcome the disadvantages of early monolithic systems

Microkernel architecture : In microkernel architecture, only the most important services are put inside the kernel and rest of the OS service are present in the system application program.

Hybrid architecture : Combine the best functionalities of all these approaches and hence this design is termed as the hybrid structured operating system

Question 9

What are the differences between Batch processing system and Real Time Processing
System?

Answer 9

Batch processing systems analyze programs and categorize them into batches based on
similarities. Real Time systems respond to activities within a certain amount of time.

Question 10

A batch & real time are used for which type of applications? Name 2 different ones for each

Answer 10

Batch: Payroll in large companies, banking environments

Real Time: Air Traffic Controllers, Reservation Systems

Question 11

What is the difference between Job and Process?

Answer 11

A process is what’s doing the work, more so how a job is done, meanwhile a job is a task,
something that is done by the system.

Question 12

What are the advantages of Multiprocessing or Parallel System?

Answer 12

Multiprocessing systems can complete more work in one amount of time as the focus is allowed to
be on multiple things as stated in the name, allowing for multitasking. Parallel systems put all this
processing powers focus towards one job at a time, meaning each job is completed quicker
individually.

Question 13

What are the differences between Real Time System and Timesharing System?

Answer 13

Time sharing systems do not have a time frame prioritized to respond within, there is a
multiprocessing of applications. It can be applied in systems that do not require a response within
a specific amount of time and have a need for running multiple things truly at once. A real time
system has an emphasis on giving a response within a certain amount of time and focus on one
task at a time.

Question 14

What are the differences between multiprocessing and multiprogramming?

Answer 14

multiprogramming uses a time sharing environment where multiple programs are not actually being done at once rather a few seconds from one thing then a few for the next and so on. Multiprocessing on the other hand has multiple processors which
allows each processor to focus on a different task at once.

Question 15

What is scheduling? What criteria affect the scheduler’s performance?

Answer 15

Scheduling is a key portion of the operating system, it’s purpose is to balance load on the system
when sharing system resources. The quality of CPU in the system would affect this performance.

Question 16

What is the purpose of Memory Management?

Answer 16

Memory management is important because it maintains track of where memory is being allocated,
if it is free, where it needs to be received, and how much. This functionality is vital because it
maintains efficiency in an environment with multiple requirements from different locations.

Question 17

hat is the significant difference between the five-state and seven-state model?

Answer 17

The seven state model is basically the five state model but with two extra suspended states.

Question 18

What occurs during the new state?

Answer 18

A new process is made but is not yet loaded into the main memory, when there is enough space
available for the new process it is moved to the main memory by the long term scheduler. Initializes PCB and pointers.

Question 19

What occurs during the exit state?

Answer 19

The process is completed or aborted.

Question 20

How is the PCB different between two processes? How are they the same?

Answer 20

The base/foundational form is consistent although the two processes themselves have their own
different respective data.

Question 21

How can an instruction trace be used?

Answer 21

It can assure functionality confirming that processes are moving and operating as intended.

Question 22

List three general categories of information in a PCB.

Answer 22

process state information
process identification
process control information

Question 23

What is Linux?

Answer 23

Linux is an open source operating system that manages the resources and system hardware

Question 24

Describe the components of the Linux Operating system.

Answer 24

Describe the components of the Linux Operating system.
Kernel: Manages as well as interacts with the system hardware
System Library: special programs/functions that implement the majority of
the OS’ functionality
System Utility: Compiler, System software, User utility programs, etc.
provides the OS functionality to the user.

Question 25

What are the main features of the Linux Operating system?

Answer 25

It’s open source, it has a hierarchical file structure, it’s portable, multi-
user, secure

Question 26

Describe the Architecture of the Linux OS.

Answer 26

The Linux OS architecture consists of a few major components or layers,
first being the hardware (CPU, etc.) then is the Kernel which takes care of
most of the OS functionality, following the Kernel is the Shell, which is
basically the interface that works between the user and the Kernel. Finally
there are utilities – the compiler, software, and so on.

Question 27

What are the benefits of multithreading?

Answer 27

Multithreading brings many benefits such as a reduced overhead,
meaning that one thread being blocked wouldn’t hold up the rest. This is
great for efficiency when multiple threads are working independently.
Other benefits could be just overall improved communication and speeds.

Question 28

Why use threads?

Answer 28

Threads allow for multiple tasks to be focused on at once, it reduces
overall overhead on the computer itself and generally increases overall
performance allowing for quicker smoother processing.

Question 29

How does a Real-time system differ from other systems?

Answer 29

A real time system differs from other systems in the sense that it works under a time constraint, its purpose is to serve applications in real time as stated in its name. Real time systems always function under fixed time constraints or system failure ensues.

Question 30

2. What is the difference between a hard and soft deadline?

Answer 30

A hard deadline is a harsher requirement in that if the deadline were to be missed it would result in system failure, however missing a soft deadline results in a drop in quality and usability but not system failure.

Question 31

Define CPU utilization, throughput, turnaround time, waiting time and response time. What is the significance of response time?

Answer 31

CPU utilization is how active the CPU actually is. Throughput is the number of completed processes in a unit time. Turnaround time is the time it takes from the submission of a process to completion. Waiting time is how long a process spends waiting for the CPU.
Response time is the time it takes from submission of a process to the first response. The significance of response time is so that there is no delay or idle time, in other words “lag”.

Question 32

What does it mean for the dispatcher to preempt a process?

Answer 32

This is when a process is switched from the CPU by the dispatcher before it is completed.

Question 33

What are the advantages of the multilevel feedback algorithm vs. the multilevel queue Algorithm?

Answer 33

The advantages of a multilevel feedback algorithm are that the process priority is dynamic which allows movement between the queue which prevents starvation, a problem that can occur with the multilevel queue as priority is fixed there meaning all processes in a single queue must be executed before any others can be executed.

Question 34

What is the difference between preemptive and non preemptive scheduling?

Answer 34

In preemptive scheduling there is a fixed amount of time the CPU is allocated to the processes. Non-preemptive scheduling means that there is no time limit and the CPU can allocate to processes until it ends or is swapped to a different state.

Question 35

In a Uniprocessor scheduler what is the best algorithm?

Answer 35

A round robin algorithm would be best for a uniprocessor scheduler because of its lack of starvation and having good response times and ease of implementation, making it more widely used and popular.

Question 36

What are some of the concerns about multiprocessor scheduling?

Answer 36

There is a large amount of overhead, there would be more waiting time in comparison to a uniprocessor variation.

Question 37

How would CPU utilization be used as a performance criterion in a scheduling algorithm? 5 points

Answer 37

CPU utilization speaks to how well and efficiently the CPU is being used, too much idle time would represent badly meaning that a CPU should aim to be as busy as possible as this would be the positive criteria in a scheduling algorithm.