Operating System for IBPS SO IT Officer 2026: Complete Notes with MCQs

Operating System for IBPS SO IT Officer 2026 is one of the most important topics in the Professional Knowledge section because questions from OS are usually concept-based, direct, and scoring.

If you are preparing for IBPS SO IT Officer, you cannot skip Operating System. Topics like process management, CPU scheduling, deadlock, memory management, paging, segmentation, file system, and semaphores appear again and again in IT exams. The good part is that OS is not difficult if you revise it in the right order.

This article is designed as a complete revision guide. You will get short notes, tables, important concepts, examples, MCQs, and a revision plan. For the official exam updates, always check the IBPS official website. For your complete IT subject preparation, you can also read our IBPS SO IT Officer Professional Knowledge Notes.

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Why Operating System Is Important for IBPS SO IT Officer

An Operating System is system software that acts as an interface between the user and computer hardware. It manages resources like CPU, memory, files, input-output devices, and processes.

Examples of operating systems include:

Windows
Linux
macOS
Android
iOS
Unix

For IBPS SO IT Officer, Operating System questions are usually asked from basic and medium-level concepts. You do not need to study very deep research-level OS theory, but you must understand the standard definitions and differences.

The most important OS areas are:

Process Management
CPU Scheduling
Deadlock
Memory Management
Paging and Segmentation
Virtual Memory
File System
Semaphores
Threads
System Calls

If your DBMS and Computer Networks are already strong, OS can become your next high-scoring subject. You can revise DBMS separately from our DBMS for IBPS SO IT Officer 2026 guide.

For extra conceptual reference, you can also check the GeeksforGeeks Operating System tutorial while revising difficult topics.

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Operating System for IBPS SO IT Officer 2026: Important Topics

Here is the topic-wise priority list:

Priority	Topic	Importance
High	Process Management	Frequently asked
High	CPU Scheduling	Formula + concept based
High	Deadlock	Very important
High	Memory Management	Common in MCQs
Medium	Paging and Segmentation	Concept-based
Medium	Virtual Memory	Important
Medium	File System	Direct questions
Medium	Semaphores	Synchronization topic
Medium	Threads	Basic difference questions
Low-Medium	System Calls	Direct definitions

If time is limited, revise process, scheduling, deadlock, memory management, paging, and virtual memory first.

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1. What is an Operating System?

An Operating System is a program that manages computer hardware and provides services to application software.

Simple definition:

Operating System = Manager of computer resources

Main functions of OS:

1. Process management
2. Memory management
3. File management
4. Device management
5. Security
6. User interface
7. Error detection
8. Resource allocation

Example:

When you open a browser, play music, download a file, and type in a document at the same time, the OS manages CPU time, memory, input-output devices, files, and background processes.

That is why OS is called a resource manager.

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2. Program vs Process

This is a very common exam concept.

Program	Process
Passive entity	Active entity
Stored on disk	Loaded in memory
Does not execute by itself	Executes under CPU
Example: .exe file	Running instance of that file

A program becomes a process when it is loaded into memory and starts execution.

Example:

Chrome browser installed on laptop = Program
Chrome browser currently running = Process

Important point:

One program can create multiple processes.

For example, one browser may create separate processes for tabs, extensions, and background tasks.

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3. Process States

A process does not stay in one state forever. It moves from one state to another during execution.

Main process states:

State	Meaning
New	Process is being created
Ready	Waiting for CPU
Running	Currently executing
Waiting/Blocked	Waiting for I/O or event
Terminated	Execution completed

Simple flow:

New → Ready → Running → Terminated

If the process needs input/output:

Running → Waiting → Ready → Running

Example:

If a process is waiting for printer output, it moves to waiting state. When printer response is complete, it returns to ready state.

This topic is very important for Operating System for IBPS SO IT Officer 2026 because many MCQs test process states directly.

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4. Process Control Block

PCB stands for Process Control Block. It stores information about a process.

PCB contains:

Process ID
Process state
Program counter
CPU registers
CPU scheduling information
Memory management information
Accounting information
I/O status information

Simple meaning:

PCB = Identity card of a process

Whenever the OS switches from one process to another, it saves the current process information in PCB.

This is important for context switching.

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5. Context Switching

Context switching means saving the state of one process and loading the state of another process.

Example:

If CPU is executing Process A and then switches to Process B, the OS must save Process A’s current state and load Process B’s state.

Important point:

Context switching is necessary for multitasking but it adds overhead.

Why overhead?

Because during context switching, CPU is not doing useful user work. It is busy saving and loading process states.

MCQ line:

Context switching reduces CPU efficiency if it happens too frequently.

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6. Threads

A thread is the smallest unit of CPU execution. A process can have multiple threads.

Process	Thread
Heavyweight	Lightweight
Has separate memory space	Shares memory of process
Context switching is slower	Context switching is faster
Independent execution unit	Part of a process

Example:

A browser process may have multiple threads:

One thread for UI
One thread for downloading
One thread for rendering page
One thread for playing video

Threads improve performance because multiple tasks can be handled inside the same process.

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7. CPU Scheduling

CPU scheduling decides which process will get CPU next.

Why scheduling is needed?

Because multiple processes may be ready, but CPU can execute only one process at a time.

Main goals of CPU scheduling:

Maximum CPU utilization
Minimum waiting time
Minimum turnaround time
Minimum response time
Maximum throughput
Fairness

Important terms:

Term	Meaning
Arrival Time	Time when process enters ready queue
Burst Time	CPU time required by process
Completion Time	Time when process finishes
Turnaround Time	Completion Time – Arrival Time
Waiting Time	Turnaround Time – Burst Time
Response Time	First response time – Arrival Time

Formula:

Turnaround Time = Completion Time - Arrival Time

Waiting Time = Turnaround Time - Burst Time

This formula is very important for numerical scheduling questions.

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8. CPU Scheduling Algorithms

FCFS Scheduling

FCFS means First Come First Serve.

The process that arrives first gets CPU first.

Advantages:

Simple
Easy to implement

Disadvantages:

Can cause convoy effect
Average waiting time may be high

Example:

If a long process comes first, smaller processes have to wait.

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SJF Scheduling

SJF means Shortest Job First.

The process with the shortest burst time gets CPU first.

Advantages:

Minimum average waiting time
Good for batch systems

Disadvantages:

Difficult to know burst time in advance
Can cause starvation for long processes

Starvation means a process waits for a very long time.

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Round Robin Scheduling

Round Robin scheduling uses time quantum.

Each process gets CPU for a fixed time slice.

Example:

Time quantum = 4 ms

If a process is not complete in 4 ms, it goes back to the ready queue.

Advantages:

Good for time-sharing systems
Fair for all processes

Disadvantages:

Too small time quantum increases context switching
Too large time quantum behaves like FCFS

Very important MCQ:

Round Robin scheduling is used in time-sharing systems.

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Priority Scheduling

In Priority Scheduling, CPU is allocated based on priority.

Highest priority process gets CPU first.

Problem:

Low priority process may suffer starvation.

Solution:

Aging

Aging gradually increases the priority of waiting processes.

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9. Deadlock

Deadlock occurs when two or more processes wait forever for resources held by each other.

Simple example:

Process P1 holds Resource A and waits for Resource B.
Process P2 holds Resource B and waits for Resource A.
Both keep waiting forever.

This is deadlock.

Deadlock is one of the most important topics in Operating System for IBPS SO IT Officer 2026.

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10. Four Necessary Conditions for Deadlock

Deadlock can occur if all four conditions exist together.

Condition	Meaning
Mutual Exclusion	Resource cannot be shared
Hold and Wait	Process holds one resource and waits for another
No Preemption	Resource cannot be forcibly taken
Circular Wait	Processes wait in circular chain

Shortcut:

M H N C
Mutual Exclusion
Hold and Wait
No Preemption
Circular Wait

If any one condition is removed, deadlock can be prevented.

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11. Deadlock Handling Methods

There are four main ways to handle deadlock:

1. Deadlock Prevention
2. Deadlock Avoidance
3. Deadlock Detection
4. Deadlock Recovery

Deadlock Prevention

Break one of the four necessary conditions.

Example:

If circular wait is prevented, deadlock cannot occur.

Deadlock Avoidance

The system checks whether resource allocation keeps the system in a safe state.

Important algorithm:

Banker's Algorithm

Banker’s Algorithm is used for deadlock avoidance.

Deadlock Detection

The system allows deadlock but detects it later.

Deadlock Recovery

After detecting deadlock, the system recovers by:

Terminating processes
Taking resources back
Rolling back process state

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12. Memory Management

Memory management is the function of OS that manages main memory.

Main goals:

Allocate memory to processes
Track used and free memory
Protect memory space
Improve memory utilization
Support multitasking

Important memory terms:

Term	Meaning
Logical Address	Address generated by CPU
Physical Address	Actual address in memory
Address Binding	Mapping program instructions/data to memory
Memory Allocation	Assigning memory to process

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13. Paging

Paging is a memory management scheme in which process is divided into fixed-size pages and memory is divided into fixed-size frames.

Term	Meaning
Page	Fixed-size block of process
Frame	Fixed-size block of physical memory
Page Table	Maps pages to frames

Important point:

Paging removes external fragmentation.

But paging can cause internal fragmentation.

Example:

If page size is 4 KB and process needs 10 KB, it uses 3 pages = 12 KB. The unused 2 KB is internal fragmentation.

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14. Segmentation

Segmentation divides a program into variable-sized logical segments.

Examples of segments:

Code segment
Data segment
Stack segment
Function segment

Paging	Segmentation
Fixed-size blocks	Variable-size blocks
Based on physical memory management	Based on logical program structure
Uses page table	Uses segment table
Can cause internal fragmentation	Can cause external fragmentation

Exam point:

Paging is physical division.
Segmentation is logical division.

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15. Virtual Memory

Virtual memory allows execution of processes that may not be completely loaded into main memory.

Simple meaning:

Virtual memory gives an illusion of larger memory.

It uses disk space as an extension of RAM.

Important concept:

Demand Paging

In demand paging, pages are loaded into memory only when required.

If required page is not in memory, it causes:

Page Fault

A page fault occurs when a process tries to access a page that is not currently in physical memory.

For more technical depth, you can refer to TutorialsPoint Operating System notes while revising page replacement and memory topics.

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16. Page Replacement Algorithms

When memory is full and a new page is needed, OS must replace an existing page.

Important page replacement algorithms:

Algorithm	Meaning
FIFO	Replace oldest page
LRU	Replace least recently used page
Optimal	Replace page not needed for longest time
LFU	Replace least frequently used page

Most important:

LRU = Least Recently Used
FIFO = First In First Out
Optimal gives best result but is difficult to implement practically.

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17. File System

File system manages files and directories on storage devices.

Main functions:

Create file
Delete file
Read file
Write file
Manage directories
Control access permissions
Track storage location

Common file operations:

open
read
write
close
delete
rename

File attributes:

Name
Type
Size
Location
Protection
Creation time
Modification time
Owner

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18. Semaphores

Semaphore is a synchronization tool used to control access to shared resources.

Types of semaphores:

Type	Meaning
Binary Semaphore	Values 0 and 1
Counting Semaphore	Values can be more than 1

Main operations:

wait()
signal()

Semaphore helps solve critical section problems.

Important:

Semaphore is used for process synchronization.

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19. Critical Section

Critical section is the part of program where shared resources are accessed.

Example:

If two processes are updating the same bank account balance, the update section must be protected.

Critical section problem requires:

Mutual Exclusion
Progress
Bounded Waiting

This topic is important because banking systems need correct transaction handling and synchronization.

You can connect this with DBMS transaction concepts from our SQL for IBPS SO IT Officer 2026 article.

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20. System Calls

System calls provide interface between user programs and operating system.

Examples:

Process control
File management
Device management
Information maintenance
Communication
Protection

Simple meaning:

A program uses system calls to request OS services.

Example:

When a program wants to read a file, it requests the OS through a system call.

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Operating System Quick Revision Table

Topic	Must Remember
OS	Resource manager
Process	Program in execution
Thread	Lightweight process
PCB	Stores process information
Context Switching	Switching CPU from one process to another
FCFS	First process gets CPU first
SJF	Shortest burst time first
Round Robin	Time quantum based
Deadlock	Processes waiting forever
Banker’s Algorithm	Deadlock avoidance
Paging	Fixed-size memory blocks
Segmentation	Logical variable-size blocks
Virtual Memory	Illusion of large memory
Page Fault	Required page not in memory
Semaphore	Synchronization tool

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30 Important MCQs on Operating System for IBPS SO IT Officer 2026

Q1. Operating System is mainly used to manage:
A. Hardware resources only
B. Software resources only
C. Computer resources
D. Internet speed

Answer: C. Computer resources

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Q2. A program in execution is called:
A. File
B. Process
C. Thread
D. Command

Answer: B. Process

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Q3. PCB stands for:
A. Program Control Block
B. Process Control Block
C. Process Code Block
D. Program Code Binary

Answer: B. Process Control Block

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Q4. Which state means the process is waiting for CPU?
A. Running
B. Ready
C. Waiting
D. Terminated

Answer: B. Ready

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Q5. Context switching means:
A. Deleting a process
B. Switching CPU from one process to another
C. Increasing memory size
D. Creating a file

Answer: B. Switching CPU from one process to another

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Q6. Which scheduling algorithm uses time quantum?
A. FCFS
B. SJF
C. Round Robin
D. Priority Scheduling

Answer: C. Round Robin

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Q7. Which scheduling algorithm may cause convoy effect?
A. FCFS
B. Round Robin
C. Priority
D. Multilevel Queue

Answer: A. FCFS

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Q8. Which scheduling algorithm gives CPU to the shortest burst time process?
A. FCFS
B. SJF
C. Round Robin
D. FIFO

Answer: B. SJF

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Q9. Starvation can be solved using:
A. Paging
B. Aging
C. Fragmentation
D. Segmentation

Answer: B. Aging

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Q10. Deadlock occurs when processes:
A. Execute quickly
B. Wait forever for resources
C. Use less memory
D. Complete successfully

Answer: B. Wait forever for resources

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Q11. How many necessary conditions are required for deadlock?
A. 2
B. 3
C. 4
D. 5

Answer: C. 4

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Q12. Which is not a necessary condition for deadlock?
A. Mutual exclusion
B. Hold and wait
C. Circular wait
D. Multiprocessing

Answer: D. Multiprocessing

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Q13. Banker’s Algorithm is used for:
A. CPU scheduling
B. Deadlock avoidance
C. File allocation
D. Page replacement

Answer: B. Deadlock avoidance

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Q14. Paging divides process into:
A. Segments
B. Pages
C. Threads
D. Files

Answer: B. Pages

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Q15. Physical memory is divided into:
A. Pages
B. Frames
C. Segments
D. Blocks only

Answer: B. Frames

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Q16. Paging mainly removes:
A. Internal fragmentation
B. External fragmentation
C. Deadlock
D. Starvation

Answer: B. External fragmentation

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Q17. Segmentation is based on:
A. Fixed-size blocks
B. Logical division of program
C. Only CPU speed
D. File size

Answer: B. Logical division of program

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Q18. Virtual memory gives illusion of:
A. Smaller memory
B. Larger memory
C. No memory
D. Only cache memory

Answer: B. Larger memory

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Q19. Page fault occurs when:
A. Page is in memory
B. Page is not in memory
C. CPU is idle
D. File is deleted

Answer: B. Page is not in memory

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Q20. LRU stands for:
A. Last Recently Used
B. Least Recently Used
C. Long Run Utility
D. Low Resource Usage

Answer: B. Least Recently Used

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Q21. FIFO page replacement removes:
A. Newest page
B. Oldest page
C. Smallest page
D. Largest page

Answer: B. Oldest page

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Q22. Semaphore is used for:
A. Process synchronization
B. File compression
C. Virus scanning
D. Printing only

Answer: A. Process synchronization

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Q23. Binary semaphore can have values:
A. 0 and 1
B. 1 and 2
C. 2 and 3
D. Any negative value

Answer: A. 0 and 1

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Q24. Critical section is a part of program where:
A. CPU is stopped
B. Shared resource is accessed
C. File is deleted
D. Internet is connected

Answer: B. Shared resource is accessed

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Q25. A thread is also called:
A. Heavyweight process
B. Lightweight process
C. Dead process
D. File process

Answer: B. Lightweight process

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Q26. Which memory management technique uses page table?
A. Paging
B. Scheduling
C. Deadlock
D. File allocation

Answer: A. Paging

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Q27. Which algorithm gives theoretically minimum page faults?
A. FIFO
B. LRU
C. Optimal
D. Random

Answer: C. Optimal

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Q28. File system is used to manage:
A. Only CPU
B. Files and directories
C. Only RAM
D. Only keyboard

Answer: B. Files and directories

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Q29. System calls provide interface between:
A. User program and OS
B. CPU and monitor only
C. RAM and hard disk only
D. Keyboard and mouse

Answer: A. User program and OS

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Q30. Round Robin scheduling is mainly used in:
A. Batch systems
B. Time-sharing systems
C. File systems
D. Deadlock systems

Answer: B. Time-sharing systems

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Last 7 Days Revision Plan for OS

Day	Topics
Day 1	OS basics, process, PCB, process states
Day 2	CPU scheduling algorithms
Day 3	Deadlock and Banker’s Algorithm
Day 4	Memory management, paging, segmentation
Day 5	Virtual memory and page replacement
Day 6	File system, semaphores, critical section
Day 7	Full revision + 100 MCQs

Daily practice rule:

Revise notes for 45 minutes
Solve MCQs for 45 minutes
Write mistakes in error notebook
Revise wrong questions next day

This is the fastest way to improve your score.

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Final Thought

Operating System for IBPS SO IT Officer 2026 is a scoring subject if you revise it with short notes and MCQs. Do not study OS like a full semester subject. Focus on exam-oriented topics like process management, scheduling, deadlock, memory management, paging, segmentation, virtual memory and semaphores.

Your target should be simple:

Clear concepts
Revise differences
Practice MCQs
Repeat weak topics

If you revise OS along with DBMS, SQL, Computer Networks and Data Structures, your Professional Knowledge preparation will become much stronger. For complete subject-wise preparation, also read the IBPS SO IT Officer Syllabus 2026 and Computer Networks for IBPS SO IT Officer 2026.

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