PART – A

1. List and briefly define the four main elements of a computer? [R]
 Processor – Controls the operation of the computer & performs its data processing functions

 Main memory – Stores data & programs.it is volatile.

 I/O modules – Move data between the computer & its external environment such as disks,
communication equipment & terminals.

 System Bus – Provides for communication among processors, main memory & I/O modules.

2. Define the two main categories of processor register? [R]

Two categories are
User- visible registers: - It Enable the machine or assembly language programmer to
minimize main memory references by optimizing register use.
Control & Status registers: - Registers used by the processor to control the operation of the
processor.

3. What is an Interrupt? [R]

 Interrupt are provided primarily as way to improve processor utilization.

 It is a mechanism by which other modules( I/O, Memory) may interrupt the normal sequencing of
the processor.
Classes of interrupts:-

 Program

 Timer

 I/O

 Hardware failure

4. How are multiple interrupt dealt with? [An]

Two approaches can be taken to dealing with interrupts

 Disabled Interrupt – Processor ignores any new interrupt request signal.

 Define Priority for interrupt – It allows an interrupt of higher priority.

5. What characteristics distinguish the various elements of a memory hierarchy? [R]

Characteristics are

1. Cost Per bit

2. Capacity
3. Access Time
4. Frequency of access to the memory by the processor
6. What is Cache Memory? [R]
1. Cache memory is invisible to the OS

2. It interacts with other memory management hardware

3. Cache contains a copy of a portion of main memory .

7. List and briefly define 3 Techniques of I/O operation? [R]

 Programmed I/O

 Interrupt Driven I/O

 Direct memory access

8. What is the distinction b/w spatial locality & temporal locality? [An]
Temporal locality refers to the reuse of specific data and/or resources within relatively small time
durations.
Spatial locality refers to the use of data elements within relatively close storage locations.
Sequential locality, a special case of spatial locality, occurs when data elements are arranged and accessed
linearly, e.g., traversing the elements in a one- dimensional array.

9. Define Locality of Reference [R]

Locality of reference, also known as the principle of locality, is the phenomenon of the same value or
related storage locations being frequently accessed.

There are two basic types of reference locality.

o Temporal locality refers to the reuse of specific data and/or resources within relatively small time durations.
o Spatial locality refers to the use of data elements within relatively close storage locations.
o Sequential locality, a special case of spatial locality, occurs when data elements are arranged and accessed
linearly, e.g., traversing the elements in a one- dimensional array.

10. What is an operating system? (NOV/DEC 2013) [R]

An operating system is a program that manages the computer hardware. it act as an intermediate
between a user‘s of a computer and the computer hardware. It controls and coordinates the use of t h e
hardware among the various application

programs for the various users.

11. What are the 3 objective of an OS Design? [R]

 Convenience – An OS makes a computer more convenient to use

 Efficiency -- An OS allows the system resources to be used in efficient manner

  Ability to Evolve – An OS Constructed in such a way as to permit the effective development, testing &
introducing new function.

12. List the Services of operating system function. (NOV/DEC 2013) [R]
1. Program development
2. Program execution
3. User Interface
4. I/O Operations
5. File system Manipulation
6. Communication
7. Error Detection
8. Resource allocation
9. Accounting
10. Security
13. Define Kernel[R]
The kernel is a software code that resides in the central core of a operating system. It has complete
control over the system.

14. Define system call. (MAY/JUNE 2009, APRIL/MAY 2019) [R]

System Call provides the interface between running program and the OS User can request any
services from OS through System Call.
Categories of system call:-

 File management

 Process Management
 Inter process Communication

 I/O Device Management

 Information Processing & Maintenance

15. What is System Programs? (APRIL/MAY 2011) [R]

System programs provides an convenient environment to the user for developing and executing the
programs.

Categories:-

1. File management
2. Status Information
3. File Modification
4. Programming language support
5. Program loading & execution
6. Communication
16. What is Boot strapping? [R]
The boot program is stored on disk with predetermined address called boot sector. The boot program then
loads the operating system into memory to startup the computer this arrangement is known as bootstrapping.

17. Difference b/w Monolithic & Microlithic. [An]

Monolithic Micro lithic

Kernel size is large Kernel size is small

OS is Complex to design OS is easy to Design Implement &

Install

Request may be serviced faster Request may be serviced slower

All OS services are included in the Kernel Provides only IPC and low level
Kernel Device management services

18. What is Multiprogramming? (MAY/JUNE 2013) [R]

Multi Programming increases CPU Utilization by organizing jobs so that the CPU always has one to execute.
Advantage:-

 It increase CPU utilization

 It makes efficient use of the CPU overlapping the demands for the CPU & I/O devices

 Increased throughput.

 Lower response time.

19. Define Real Time System [R]

Real time system is one that must react to input & responds to them quickly. A real time system has
well defined, fixed time constants.

20. What does the CPU do when there are no user programs to run? (NOV/DEC 2011) [R]
The CPU will always do processing. Even though there are no application programs running, the operating
system is still running and the CPU will still have to process.
21. Describe the actions taken by a kernel to context-switch between processes.
[An] (NOV/DEC 2013)
In general, the operating system must save the state of the currently running process and restore the state of
the process scheduled to be run next. Saving the state of a process typically includes the values of all the CPU
registers in addition to memory allocation. Context switches must also perform many architecture-specific
operations, including flushing data and instruction caches.
22. What is multicore processor? [R]
Hardware has been to place multiple processor cores on the same physical chip, resulting in a multicore
processor. Each core maintains its architectural state and thus appears to the operating system to be a separate
physical processor.

23. What is memory stall? [R]

Researchers have discovered that when a processor accesses memory, it spends a significant amount of time
waiting for the data to become available. This situation, known as a memory stall , may occur for various reasons,
such as a cache miss.

24. What is Boot strapping? [R]

 The boot program is stored on disk with predetermined address called boot sector.
 The boot program then loads the operating system into memory to startup the computer. This arrangement is
known as bootstrapping.

25. Can multiple user level threads achieve better performance on a multiprocessor system than a single
processor system? Justify your answer. (MAY/JUNE 2014 ) [An]
We assume that user-level threads are not known to the kernel. In that case, the answer is because the
scheduling is done at the process level. On the other hand, some OS allows user-level threads to be assigned to
different kernel-level processes for the purposes of scheduling. In this case the multithreaded solution could be
faster
26. Mention the circumstances that would a user be better off using a time-sharing system rather than a PC
or a single user workstation? (MAY/JUNE 2014) [An]
A user is better off fewer than three situations: when it is cheaper, faster, or easier. For example:
1. When the user is paying for management costs and the costs are cheaper for a time-sharing system
than for a single-user computer.
2. When running a simulation or calculation that takes too long to run on a single PC or workstation.

3. When a user is travelling and doesn't have laptop to carry around, they can connect remotely to a time-
shared system and do their work.

27. Do timesharing differ from Multiprogramming? If so, How?(APR/MAY 2015) [An]

Time Sharing: here, OS assigns some time slots to each job. Here, each job is executed according to the
allotted time slots.
Job1: 0 to 5 Job2: 5 to 10 Job3: 10 to 15 Multi-
Tasking: in this operating system, jobs are executed in parallel by the operating system. But, we
can achieve this multi-tasking through multiple processors (or) multicore CPU only.
CPU1: Job1 CPU2: Job2 CPU3: Job3

28. Why API s need to be used rather than system calls?(APR/MAY 2015) [An]
System calls are much slower than APIs (library calls) since for each system call, a context switch has to
occur to load the OS (which then serves the system call).Most details of OS interface hidden from programmer by
API Managed by run-time support library (Set of functions built into libraries included with compiler.)

29. Describe the actions taken by a thread library to context switch between user- level threads. [An]
The user-level threads are known only within a given process. To context switch, we only need to save the
thread-specific context: the program counter, CPU registers, and the thread-specific stack pointer
30. What is the purpose of system programs? (May/Jun 2016) [R]
System programs can be thought of as bundles of useful system calls. They provide basic functionality to
users so that users do not need to write their own programs to solve common problems.

31. What are the advantages of peer-to-peer systems over client-server systems? (May/Jun 2016) [R]
 It is easy to install and so is the configuration of computers on this network, all the resources and contents
are shared by all the peers, unlike server-client architecture where Server shares all the contents and
resources.

 P2P is more reliable as central dependency is eliminated. Failure of one peer doesn‘t affect the functioning
of other peers. In case of Client –Server network, if server goes down whole network gets affected.

 There is no need for full-time System Administrator. Every user is the administrator of his machine. User
can control their shared resources.

 The over-all cost of building and maintaining this type of network is comparatively very less.

32. Compare and contrast DMA and cache memory. (Nov/Dec 2015) [An]
 DMA is a hardware device that can move to/from memory without using CPU instructions.

 For instance, a hardware device (lets say, your PCI sound device) wants audio to play back. You can either:

 Write a word at a time via a CPU mov instructions.

 Configure the DMA device. You give it a start address, a destination, and the number of bytes to copy. The
transfer now occurs while the CPU does something else instead of spoon feeding the audio device.

 DMA can be very complex (scatter gather, etc), and varies by bus type and system.

33. Write the difference between Batch systems and Time sharing systems. (Nov/Dec 2015) [An]
 A batch is a sequence of jobs. This batch is submitted to batch processing operating systems, and output
would appear some later time in the form of a program or as program error. To speed up processing similar
jobs are batched together.

 The major task of batch operating systems is to transfer control automatically from one job to next. Here the
operating is always in the memory.

 Time sharing or multi-tasking is a logical execution of multiprogramming. Multiple jobs are executed by the
CPU switching between them. Here the computer system provides on line communication between the user
and the system.

 Here the CPU is never idle. Time shared operating system allows many users to share the computer
simultaneously.

 Time sharing systems requires some sort of memory management and protection.
34. How does an interrupt differ from a trap or what is the difference between trap and interrupt?
(NOV/DEC 2016) [An] (APR/MAY 2018)
An interrupt handler is called to deal with the cause of the interrupt; control is then returned to the
interrupted context and instruction. A trap is a software-generated interrupt. An interrupt can be used to signal
the completion of an I/O to obviate the need for device polling.
35. What are the disadvantages of multiprocessor systems? (NOV/DEC 2016) [R]
 If one processor fails then it will affect in the speed

 Multiprocessor systems are expensive.

 Complex OS is required.

 It's more complex.

 It requires context switching which slightly impacts

36. What are the objectives of operating systems? (APR/MAY 2017) [R] (NOV/DEC 2017) [R]
An OS is a program that controls the execution of application programs and acts as an interface between
applications and the computer hardware. Objectives of OS: Convenience: An OS makes a computer more
convenient to use. Efficiency: An OS allows the computer system resources to be used in an efficient manner.
37. What is SYS GEN and system boot ?[R] (NOV/DEC 2017) (NOV/DEC 2021)
SYS GEN :It is the Short for SYStem GENeration, sysgen is a utility that enables an operating system to
configure hardware and software setups properly.
System Boot:
Booting the system is done by loading the kernel into main memory, and starting its execution.
The CPU is given a reset event, and the instruction register is loaded with a predefined memory
location, where execution starts.
38. Mention the purpose of system calls.[R] (APR/MAY 2018)
 System calls allow user-level processes to request services of the operating system.

 If a file system requires the creation or deletion of files.

 Reading and writing from files also require a system call.

 Creation and management of new processes.

 Network connections also require system calls. This includes sending and receiving packets.

 Access to a hardware devices such as a printer, scanner etc. requires a system call.

39. What is dual mode operation and what is the need of it?(APRIL/MAY 2019) In monitor mode, the
CPU can use all instructions and access all areas of memory.
In user mode, the CPU is restricted to unprivileged instructions and a specified area of memory. User code
should always be executed in user mode and the OS design ensures that it is.
40. Distinguish between Multicore and Multiprocessor. (NOV/DEC 2021)
Multicore systems have a single processor with multiple processing units. These processing units are
termed cores. On the other hand, multiprocessor systems have two or more processors. A multiprocessor
system is much more reliable than a multicore system but a multiprocessor system has a complex configuration
compared to a multicore system. Both multicore processors and multiprocessors are used to speeding up the
computing process of the system.
PART – B &C

1. Explain Operating System Structure and components. [R] (APRIL/MAY 2010, NOV/DEC 2013)
2. Discuss multiprocessor systems in detail. [U] (MAY/JUNE 2013)

3. Explain in detail the types of system calls provided by a typical operating system.[R] (NOV/DEC 2012)

4. Explain the purpose of system calls and discuss the calls related to device management and communications in
brief. [An] (MAY/JUNE 2014)
5. Explain the concepts of virtual machines, their implementation and benefits in details.[An] (MAY/JUNE 2014)
6. What is a virtual machine? List out the advantages of virtualization. Explain the creation of a Virtual
machine with a architecture diagram [An] (NOV/DEC 2013)
7. Write short notes on operating system services and components. [U] (MAY/JUNE 2012)
8. Write in detail about the real time system and multiprocessor system. [U]
9. Explain the various types of System calls with an example for each?[U] (APR/MAY 2015)

10. Discuss about the functionality of system boot with respect to operating system.[An] (APR/MAY 2015)

11. Discuss about the evolution of virtual machines. Also explain how virtualization could be implemented in
operating systems. [Ap] (APR/MAY 2015)
12. Sketch the structure of Direct Memory Access in detail. [U] (APR/MAY 2015)
13. (i) With neat sketch discuss computer system overview
(ii) Enumerate the different operating system structure and explain with neat sketch.[U] (Nov/Dec 2015)

14. (i) State the basic functions of OS and DMA.

(ii) Explain system calls, system programs and OS generation. [U] (Nov/Dec 2015)
15.(i) Distinguish between the client-server and peer-to-peer models of distributed systems.
(ii) Describe three general methods for passing parameters to the operating system with example.[An]
(MAY/JUNE 2016)
16.(i) How could a system be designed to allow a choice of operating systems from which to boot? What
would the
bootstrap program need to do? [Ap]
(ii) Describe the differences between symmetric and asymmetric multiprocessing. What are three advantages
and one disadvantage of multiprocessor systems? [An] (MAY/JUNE 2016)
17.(i) Describe a mechanism for enforcing memory protection in order to prevent a program from modifying the
memory associated with other programs (8)[An] (NOV/DEC 2016)
(ii)What are the advantages and disadvantages of using the same system call interface for manipulating
both files and devices? (8) [An] (NOV/DEC 2016)
18.(i) State and explain the major activities of an operating system with regard to filemanagement? (8)[U]
(NOV/DEC 2016)
(ii)Discuss the different multiprocessor organizations with block diagrams [An] (8) (NOV/DEC 2016)

19.(i)Explain the concept of multiprocessor and Multicore organizations (7) [U] (APR/MAY 2017)
(ii) Discuss about direct memory access (6) [U] (APR/MAY 2017)
20.(i) Explain the various structures of an operating system (8) [U](APR/MAY 2017)
(ii)Describe system calls and system programs in detail with neat sketch (5) [An] (APR/MAY 2017)
21. Explain Cache memory and its mapping. [U](13) (NOV/DEC 2017)
22. Describe evolution of operating system. [U](13) (NOV/DEC 2017)
23. State the operating system structure. Describe the operating-system operations in detail. Justify the reason
why the lack of a hardware-supported dual mode an cause serious shortcoming in an operating system? (13) [U]
(APR/MAY 2018)
ii) Describe the major activities of operating system with regards to file management.[U](5) (APR/MAY 2018)

24. Explain in detail the difference architecture of OS starting from simple structure, Layered structure, micro
kernel, modules and hybrid system with suitable example OS structures, including Google‘s android. (13)
(APR/MAY 2019)
25. (i) Discuss the pros and cons of single processor system, multi core system and clustered system. (8)
(ii) Explain the steps involved to transfer the stored historical information in a magnetic tapes to the CPU for
further processing through various storage device.(5) (APR/MAY 2019)

26. (i) Explain important and need of cache with its working principle. (7) (NOV/DEC 2021)
(ii) What is function of DMA operation? Explain with neat diagram. (6)
27. (i) Discuss in detail about the varies memory hierarchies with neat block diagram. (7)
(ii) Discuss about the functionality of system boot with respect to operating system. (6)
(NOV/DEC 2021)