Section-A

1.What are the main objectives of operating system?

the main objectives of operating system are:

• Convenience
• Hardware abstraction
• Efficiency

2. What is process scheduling?

Process scheduling is a crucial aspect of multiprogramming operating systems.

It involves managing the CPU’s allocation of time among competing processes.

3. What is kernel level thread?

Kernel-level threads (KLTs), also known as native threads or heavyweight

threads, are a form of threading where thread management is handled by the
operating system kernel.

4. What is an operating system?

An operating system (OS) is system software that manages computer hardware

and software resources, providing essential services for computer programs

5. What are the methods to handling deadlock?

There are several methods for handling deadlocks in operating systems are:

1. Deadlock prevention
2. Deadlock Avoidance
3. Deadlock Detection & Recovery
4. Deadlock Ignorance

6. What is a inter process communication?

Inter-process communication (IPC) refers to the mechanisms provided by an

operating system for processes to manage shared data1. It allows processes to
communicate with each other and synchronize their actions.

7. What is contiguous memory allocation?

Contiguous memory allocation is a memory management technique used by

operating systems to allocate memory to processes in contiguous blocks.
8. list the various file attributes.

file attributes provide essential information about files. Various file attribute are

1. Name
2. Identifier
3. Type
4. Location
5. Size
6. Protection
7. Time and Date

9. What are the file operations?

File operations within an operating system (OS) encompass a set of essential

tasks and actions directed at files and directories.

10.What is batch processing?

Batch processing is a technique used by computers to automate and process

multiple data jobs as a single group.

11. What is process creation?

Process creation refers to the dynamic generation of new processes by an

operating system. When a program is executed, the OS creates a process to
manage its execution.

12. What is critical section?

a critical section refers to a specific segment of code that deals with accessing
shared resources like shared memory or I/O devices.

13. What is semaphore? Mention its type.

A semaphore is a synchronization tool used in computer science to manage

access to shared resources among multiple processes or threads. Its type are:

• Binary Semaphore
• Counting Semaphore

14. What is virtual memory?

Virtual memory is a memory management technique used by operating systems

to give the appearance of a large, continuous block of memory to applications,
even if the physical memory (RAM) is limited.
15. What logical and physical address?

Logical address: A logical address, also known as a virtual address, is an

address generated by the CPU during program execution.

Physical address: A physical address refers to the actual location in the

computer’s memory hardware, such as RAM or a storage device.

16. Differentiate between multiprogramming and multitasking operating system.

Multiprogramming : Multiprogramming is a technique used in operating systems

to maximize CPU utilization by allowing multiple programs to reside in memory
simultaneously.

Multitasking : ! A multitasking operating system allows multiple tasks or

processes to run concurrently on a single computer

17. What is a thread?

A thread represents an independent sequence of instructions that can be

scheduled and executed by the CPU. it is a fundamental unit of execution
within a process.

18. What is pre-emptive scheduling?

Pre-emptive scheduling is a CPU scheduling technique used in operating

systems. It ensures that the highest-priority process gains access to the CPU as
soon as it becomes available.

19. What is race condition?

A race condition occurs in an operating system when two or more processes or

threads execute concurrently, and the outcome depends on the order of their
execution.

20. What is swapping?

Swapping in an operating system is a memory management scheme that

temporarily moves processes between the main memory and secondary storage.

21.what is dynamic loading?

Dynamic loading is a memory management technique in operating systems

where a program loads a library or other binary into memory at runtime.
 Section-B

1.Write a note on threading issues?

Threading issues in an operating system can cause problems like threads trying
to use the same data at the same time, leading to unpredictable results (race
conditions). Another issue is deadlock, where threads get stuck waiting for each
other to finish using resources. Also, thread priority inversion can happen when a
low-priority thread holds up a high-priority one. These issues can slow down the
system or make it behave unexpectedly.

2. Explain priority scheduling algorithm with example?

Priority scheduling is a CPU scheduling algorithm where each process is

assigned a priority, and the process with the highest priority is selected for
execution. This approach ensures that important or time-sensitive tasks are
executed before others. These are key characteristics are:

• Priority Assignment
• Pre-emptive or non-pre-emptive

Example: | A | B | C | A |

0 1 5 7 15

3. Write a note on Dining- Philosophers problem.?

The Dining Philosophers problem is like a brain teaser for computers. Imagine
philosophers sitting at a table, needing both food and forks to eat. The problem
arises when each philosopher needs two forks to eat but there are only as many
forks as there are philosophers. If every philosopher picks up the fork on their
right, they all end up stuck waiting for the second fork, unable to eat (deadlock).

4. Explain two types of fragmentation?

in operating systems, there are two types of fragmentation: internal

fragmentation and external fragmentation.

1. Internal Fragmentation: Internal fragmentation occurs when memory is

allocated in fixed-sized blocks or partitions, and the allocated memory is larger
than the required amount.

2. External Fragmentation: External fragmentation occurs when free memory is

scattered throughout the system in small, non-contiguous blocks.
5.Briefly explain indexed file allocation methods.

In indexed file allocation methods, file data is stored in blocks, and an index is
used to keep track of where these blocks are located. This method helps manage
files efficiently by allowing quick access and management of disk blocks.

6.Write a note on computer system organization.

Computer system organization in operating systems is like the master plan of a

bustling city. Just as a city is divided into different zones like residential,
commercial, and industrial areas, a computer system is structured into essential
components such as the CPU, memory, storage, and input/output devices. The
operating system acts as the city planner, coordinating these components to
ensure efficient operation.

7. Explain different types of semaphores.

Semaphores are synchronization tools used in concurrent programming to

manage access to shared resources and avoid race conditions. there are two
main types of semaphores are:

1. Binary Semaphores: A binary semaphore is a semaphore with only two states:

0 and 1. It is used to control access to a resource in a mutual exclusion scenario.

2. Counting Semaphores: A counting semaphore allows a range of values,

typically representing the number of available resources or permits.

8. Briefly explain free space management.

In the operating system, free space management is like organizing parking spots
in a city. It involves keeping track of available space on storage devices, such as
hard drives. The system monitors which areas are free and which are in use to
ensure efficient storage of new data without conflicting with existing data.
Effective free space management is essential for maximizing storage usage and
preventing data loss caused by insufficient space.

9. What are the functions of an operating system? Explain.

An operating system (OS) is a fundamental component of computer systems that

manages hardware resources and provides various services to applications and
users.

1. Resource Management: The OS manages hardware resources like CPU,

memory, and storage, allocating them to different programs efficiently.
 2. Process Management: It handles running programs, scheduling tasks, and
managing processes to ensure they run without conflicts.

3. Memory Management: The OS supervises memory usage, allocating and

deallocating memory for programs to prevent memory leaks.

4. File Management: It organizes and controls files on storage devices, allowing

users to store, retrieve, and manage data effectively.

5. Security: The OS enforces security measures, controls access to resources,

and protects the system from unauthorized access and malware.

6. User Interface: It provides a user-friendly interface for users to interact with

the computer system, enabling them to run applications and manage settings.

7.Device Management: The OS communicates with hardware devices like

printers, scanners, and keyboards, ensuring they function correctly and are
accessible to users.

10. Write a note on scheduling criteria?

Scheduling criteria are metrics or standards used to evaluate and determine the
effectiveness of scheduling algorithms in operating systems.

1.CPU Utilization: Keep the CPU busy to maximize efficiency.

2.Throughput: Aim to complete as many tasks as possible in a given time.

3.Turnaround Time: Minimize the time taken to execute a process from

submission to completion.

4.Waiting Time: Reduce the time processes spend waiting in the queue.

5.Response Time: Minimize the time taken to respond to user interactions.

6.Fairness: Ensure all processes get a fair share of CPU time.

11. Explain acyclic graph directories ?

Acyclic graph directories are a file organization method used in operating

systems to manage and represent file systems efficiently. This method helps in
organizing files and directories in a way that avoids cyclic dependencies, which
can lead to problems in file management and access.
12. Expiain the cinerent types of threads?

Threads are the smallest unit of execution within a process, and they enable
concurrent execution within a program. Different types of threads are used to
manage and execute multiple tasks efficiently. Some common types of threads
include:

1.User-level Threads: These threads are managed by the application and not the
operating system. They are lightweight and can be created and managed by the
application without OS intervention.

2.Kernel-level Threads: Managed by the operating system, these threads are

more robust and provide better performance but are costlier to create and
manage.

3.Lightweight Threads: Similar to user-level threads but supported by the kernel,

allowing for better coordination between threads and system resources.

13. Explain methods for handling deedlocks?

Handling deadlocks in operating systems involves various strategies to prevent,

avoid, detect, and recover from situations where processes are stuck in a state
of waiting for each other, leading to a standstill.

1. Deadlock Prevention : Deadlock prevention involves designing the system in

such a way that the conditions for deadlock are never met.

2. Deadlock Avoidance : Deadlock avoidance involves dynamically checking

resource allocation requests to ensure that they do not lead to an unsafe state,
where deadlock could occur.

3. Deadlock Detection: Deadlock detection involves allowing deadlocks to

occur but periodically checking the system to detect them.

4. Deadlock Recovery: Once a deadlock is detected, recovery methods are

used to break the deadlock and restore normal operation.

5. Manual Intervention: In some cases, manual intervention might be required

to resolve complex deadlock situations, especially in systems where automated
methods are not feasible or sufficient.
14. Write a note on segmentation.

Segmentation in the operating system is like dividing a big task into smaller parts
to make it easier to handle. It helps in organizing memory by breaking it into
segments like chapters in a book. Each segment has its own size and can grow or
shrink independently. This method allows for more efficient memory
management and helps in preventing wastage of memory space.

15. Explain any two directory structure?

Directory structures in file systems organize files and directories to facilitate

efficient data management and retrieval.

1. Single-Level Directory Structure: In a single-level directory structure, all files

are stored in a single, flat directory with no subdirectories.

2. Hierarchical Directory Structure: A hierarchical directory structure organizes

files and directories in a tree-like format with a root directory at the top and
multiple levels of nested directories.

3. Network Directory Structure: In a network directory structure, files and

directories are distributed across multiple networked systems.

4. Database Directory Structure: In a database directory structure, files are

organized and managed using a database management system (DBMS).

5. Indexed Directory Structure: An indexed directory structure uses an index or

table to keep track of the locations of files and directories.

Section-C

1.(a) Briefly discuss process control block.

A Process Control Block (PCB) is a data structure used by the operating system
to manage and track processes. It contains essential information about a
process, such as:

1. Process State: Indicates the current status of the process (e.g., running, waiting,
or ready).

2. Process ID: A unique identifier for the process.

3. Program Counter: Holds the address of the next instruction to be executed.

4. CPU Registers: Stores the process’s register values for context switching.

5. I/O Status Information: Contains information about I/O devices and resources
allocated to the process.
(b) Write a note on:

(i) Shared Memory System : A Shared Memory System is an interprocess

communication (IPC) mechanism that allows multiple processes to access a
common memory space. This shared memory region enables processes to
communicate and synchronize by reading from and writing to this memory area.

(ii) Message Passing: Message Passing is a fundamental method of interprocess

communication (IPC) where processes communicate by sending and receiving
messages through a communication channel.

2.(a) Write a note on multithreading.

Multithreading is a technique used in computer programming to execute

multiple threads concurrently within a single process. A thread is the smallest
unit of execution within a process and shares the same memory space and
resources as other threads within the same process.

(b) Write a note on threading issues.

Threading Issues refer to the challenges and complexities involved in managing

threads within an application or operating system. Threads are lightweight units
of execution within a process, and while they provide benefits such as improved
performance and resource sharing, they also introduce several issues that need
to be addressed for correct and efficient multi-threaded operation.

3. Explain deadlock detection and recovery algorithms.

Deadlock Detection and Recovery are mechanisms used by operating systems

to handle situations where processes are stuck in a state of waiting indefinitely
for resources held by each other. Deadlocks occur when a set of processes are
each waiting for resources held by others in the set, creating a cycle of
dependencies with no progress.

4.(a) Write a note on basic page replacement.

Basic Page Replacement is a fundamental concept in operating systems used

to manage memory efficiently when a process needs more memory than is
available. It involves selecting which page to remove from memory when a page
fault occurs and a new page needs to be loaded.

(b) Write a note on thrashing.

Thrashing refers to a situation in a computer system where excessive paging

occurs, severely impacting system performance. It happens when the operating
system spends more time swapping pages in and out of memory than executing
actual processes.
5. Briefly explain file protection

File Protection refers to mechanisms and strategies used to safeguard files from
unauthorized access, modification, or deletion. Ensuring file protection is crucial
for maintaining data integrity, privacy, and security within an operating system or
a file management system.

6. Explain any two types of operating system.

Type of operating system are:

1. Batch Operating Systems: An operating system that processes jobs

sequentially in batches without interactive user involvement.

2. Time-Sharing Operating Systems: An operating system designed to handle

multiple users simultaneously by rapidly switching between tasks, giving the
illusion of concurrent execution.

3. Multiprocessing Operating Systems: An operating system that supports the

use of multiple CPUs (processors) to execute multiple processes
simultaneously, enhancing performance and reliability by distributing tasks
across several processors.

4. Distributed Operating Systems: An operating system that manages a

network of separate computers and presents them as a unified system to users.

5. Real-Time Operating Systems (RTOS): An operating system designed to

process data and respond to events within strict timing constraints.

6. Network Operating Systems: An operating system that manages network

resources and services, such as file sharing, printer access, and network
security.

7. Mobile Operating Systems: An operating system designed for mobile devices

such as smartphones and tablets.

8. Embedded Operating Systems: An operating system embedded within

hardware devices to control specific functions or tasks.
7. Explain two types of threads.

Threads are fundamental units of execution within a process, allowing multiple

operations to run concurrently. There are several types of threads based on their
creation, management, and execution.

1. User Threads: Threads that are created and managed at the user level without
direct support from the operating system.

2. Kernel Threads: Threads that are created and managed directly by the
operating system’s kernel.

3. Hybrid Threads: A combination of user and kernel threads, where user-level

threads are mapped to kernel threads.

4. Lightweight Threads: Also known as "lightweight processes" or "LWP," these

are threads that share the same resources and address space as other threads
in the same process, but are scheduled independently.

5. Single-Threaded Process: A process that contains only one thread of

execution.

6. Multi-Threaded Process: A process that contains multiple threads of

execution running concurrently.

(b) Write a note on multilevel queue scheduling.

Multilevel Queue Scheduling is a CPU scheduling algorithm used by operating

systems to manage processes in a way that differentiates between various types
of processes based on their characteristics and requirements. This scheduling
approach involves dividing processes into multiple queues, each with its own
scheduling policy and priority.

8. Explain deadlock avoidance with an example.

Deadlock avoidance is a strategy used to ensure that a system remains in a safe

state by carefully managing resource allocation. The goal is to prevent a system
from entering a state where deadlock could occur by analyzing resource
requests and ensuring that they do not lead to an unsafe condition. The Banker's
Algorithm is a classic example of a deadlock avoidance technique.

9.(a) Write a note on Bounded Buffer problem.

The Bounded Buffer Problem, also known as the Producer-Consumer

Problem, is a classic synchronization problem in computer science and
operating systems. It involves coordinating processes that share a finite-size
buffer, with the goal of ensuring correct and efficient access to the buffer.
(b) What is indexed sequential file access? Explain

Indexed Sequential File Access is a file access method that combines the
advantages of both sequential and direct access to efficiently manage and
retrieve records from a file. It is particularly useful when you need to access
records in a file both in a sorted order and randomly by key values.

10.(a) Explain different categories of system calls.

System calls are the mechanisms through which user programs interact with the
operating system kernel. They provide the interface for performing various
functions that require privileged access to system resources. System calls are
typically categorized based on the type of service they provide.

1. Process Control: These system calls manage the creation, execution, and
termination of processes.

2. File Management: These system calls handle file operations, including

creation, deletion, reading, and writing.

3. Device Management: These system calls handle operations related to input

and output devices.

4. Information Maintenance: These system calls manage and retrieve

information about the system and processes.

5. Communication: These system calls manage inter-process communication

(IPC) and synchronization.

6. Memory Management: These system calls handle operations related to

memory management.

(b) Explain two operations on process.

Processes are fundamental units of execution in an operating system. They

represent programs in execution and involve various operations for their
management. Two key operations on processes are process creation and
process termination.

1. Process Creation: it is the operation of starting a new process.

2. Process Termination: Process termination is the operation of ending a

process's execution.
11. Explain the following scheduling algorithm with example.

(i) FCFS: First-Come, First-Served (FCFS) is one of the simplest and most
straightforward scheduling algorithms used in operating systems to manage
process execution. As the name suggests, FCFS schedules processes in the
order they arrive in the ready queue, without preemption.

(ii) SJF: Shortest Job First (SJF) is a CPU scheduling algorithm that selects the
process with the smallest execution time (or burst time) for execution next. SJF
aims to minimize the average waiting time for processes by always choosing the
process that has the shortest burst time.

12. Explain deadlock prevention methods.

Deadlock Prevention involves designing the operating system in such a way that
it can prevent the conditions necessary for a deadlock from occurring. Deadlock
prevention methods ensure that at least one of the necessary conditions for a
deadlock is not met, thereby avoiding the possibility of a deadlock.

(b) what is fragmentation ? explain the type of fragmentation.

Fragmentation refers to the condition where storage space is utilized

inefficiently, causing a reduction in performance and potential waste of
resources. It occurs in both memory and storage systems and is categorized into
two main types:

o internal fragmentation: Internal fragmentation occurs when allocated

memory may have more space than required by the process. This leads to
wasted space within allocated memory blocks.
o external fragmentation: External fragmentation occurs when free
memory is divided into small, non-contiguous blocks over time, making it
difficult to allocate large contiguous blocks of memory.

13.Briefly explain linked file allocation methods.

Linked File Allocation is a method used to manage files on a storage medium,

where the file's blocks are not stored contiguously but are instead linked
together in a chain-like manner. This method is designed to handle situations
where disk space is fragmented and to efficiently manage files of variable sizes.