Operating System (OS) is one of the important topics for Bihar STET Computer Science preparation. In the available Computer Science syllabus references, Operating System is included under Unit 5 and covers topics such as OS functions and types, processes, process scheduling, synchronization, deadlocks, memory management, virtual memory, file systems and I/O systems.
This article provides Bihar STET Computer Science Operating System Notes 2026 along with important MCQs for exam preparation.
Operating System – Introduction
An Operating System is system software that acts as an interface between the user and computer hardware. It manages hardware resources and provides services for application programs.
Major Functions of an Operating System
Process Management – Creation, scheduling and termination of processes.
Memory Management – Allocation and deallocation of main memory.
File Management – Creation, deletion and organization of files.
Device Management – Management of input/output devices.
Security and Protection – Protects system resources from unauthorized access.
Resource Management – Allocates CPU, memory and I/O resources.
User Interface – Provides CLI or GUI for interaction with the computer.
Types of Operating Systems
1. Batch Operating System
In a batch operating system, similar jobs are collected and executed in batches without direct interaction from the user.
2. Multiprogramming Operating System
Multiple programs are kept in main memory at the same time. The CPU switches between programs to improve CPU utilization.
3. Multitasking Operating System
It allows a user to execute multiple tasks apparently at the same time.
4. Time-Sharing Operating System
CPU time is divided into small time slices and allocated to different processes.
5. Multiprocessing Operating System
It uses two or more processors/CPU cores to execute processes.
6. Distributed Operating System
It manages a group of networked computers and attempts to provide users with a unified system environment.
7. Real-Time Operating System
A real-time OS is designed to respond to events within specified time constraints.
Examples include systems used in industrial control, robotics and embedded applications.
8. Mobile Operating System
Operating systems designed specifically for mobile devices include Android and iOS.
Process
A process is a program in execution.
A program is a passive entity stored on storage, whereas a process is an active entity.
Process States
The common process states are:
New
Ready
Running
Waiting/Blocked
Terminated
Process Control Block (PCB)
The PCB is a data structure maintained by the operating system for storing information about a process.
It may contain:
Process ID
Process state
Program counter
CPU registers
Scheduling information
Memory management information
I/O status information
Context Switching
Context switching is the process of saving the state of a running process and loading the saved state of another process.
Context switching allows the CPU to switch between processes but introduces overhead.
CPU Scheduling
CPU scheduling determines which ready process should be assigned the CPU next.
Important Scheduling Algorithms
First Come First Serve (FCFS)
The process that arrives first gets the CPU first.
Simple
Non-preemptive
Can suffer from the convoy effect
Shortest Job First (SJF)
The process with the shortest CPU burst is selected first.
SJF can provide minimum average waiting time when burst times are known accurately.
Round Robin (RR)
Each process receives a fixed amount of CPU time called a time quantum.
It is commonly associated with time-sharing systems.
Priority Scheduling
The CPU is assigned according to process priority.
Priority scheduling can be preemptive or non-preemptive.
Process Synchronization
When multiple processes access shared resources concurrently, synchronization is required to maintain data consistency.
Critical Section
A critical section is the part of a program where shared data or resources are accessed.
A proper synchronization solution should satisfy:
Mutual Exclusion
Progress
Bounded Waiting
Semaphore
A semaphore is a synchronization mechanism used to control access to shared resources.
Two commonly discussed operations are:
wait()
signal()
Semaphores may be:
Binary semaphore
Counting semaphore
Inter-Process Communication (IPC)
IPC allows processes to exchange information and coordinate with each other.
Common IPC mechanisms include:
Shared Memory
Message Passing
Pipes
Sockets
Deadlock
A deadlock occurs when a group of processes becomes permanently blocked because each process is waiting for a resource held by another process.
Four Necessary Conditions of Deadlock
Mutual Exclusion
Hold and Wait
No Preemption
Circular Wait
These four conditions are collectively known as the necessary conditions for deadlock.
Deadlock Handling
Deadlocks can be handled using:
Deadlock Prevention
Deadlock Avoidance
Deadlock Detection and Recovery
Ignoring the problem in systems where appropriate
Banker's Algorithm
The Banker's Algorithm is a deadlock avoidance algorithm.
It checks whether granting a resource request keeps the system in a safe state.
Memory Management
Memory management is responsible for allocating and deallocating memory for processes.
Important concepts include:
Contiguous allocation
Fixed partitioning
Variable partitioning
Paging
Segmentation
Virtual memory
Swapping
Paging
Paging divides:
Logical memory into pages
Physical memory into frames
A page can be loaded into any available frame.
Paging helps eliminate external fragmentation, although internal fragmentation can still occur.
Segmentation
Segmentation divides a program into logical segments such as:
Code
Data
Stack
Procedures
Unlike paging, segmentation is based on the logical structure of a program.
Virtual Memory
Virtual memory allows a system to execute processes that may not be completely loaded into physical memory.
It commonly uses secondary storage as an extension of main memory.
Demand Paging
In demand paging, a page is loaded into memory only when it is required.
If a required page is not present in memory, a page fault occurs.
Page Replacement Algorithms
Important page replacement algorithms include:
FIFO
Optimal Page Replacement
LRU
Second Chance
FIFO
The page that has been in memory for the longest time is replaced first.
LRU
The page that has not been used for the longest period of time is replaced.
Optimal
The page that will not be used for the longest period in the future is replaced.
The optimal algorithm is mainly used as a theoretical benchmark because future references are not known in advance.
Thrashing
Thrashing occurs when the system spends excessive time handling page faults and swapping pages rather than executing useful processes.
It is generally associated with insufficient memory and excessive paging activity.
File System
The file system provides a mechanism for storing, organizing and retrieving files.
Important concepts include:
Files
Directories
File descriptors
File attributes
File operations
Directory management
Common File Operations
Create
Open
Read
Write
Close
Delete
Seek
I/O System
The operating system manages communication between the CPU and input/output devices.
Important I/O techniques include:
Programmed I/O
The CPU actively checks and controls the I/O operation.
Interrupt-Driven I/O
The device generates an interrupt to notify the CPU when service is required.
DMA
Direct Memory Access (DMA) allows data to be transferred between an I/O device and main memory with limited CPU involvement.
Bihar STET Operating System Important MCQs 2026
1. What is the primary function of an operating system?
A. To design hardware
B. To manage computer resources
C. To create websites
D. To compile only Java programs
Answer: B. To manage computer resources
2. A program in execution is called:
A. Thread
B. Process
C. File
D. Instruction
Answer: B. Process
3. Which data structure contains information about a process?
A. FAT
B. PCB
C. ROM
D. Cache
Answer: B. PCB
4. PCB stands for:
A. Program Control Block
B. Process Control Block
C. Process Communication Buffer
D. Program Communication Block
Answer: B. Process Control Block
5. Which scheduling algorithm uses a time quantum?
A. FCFS
B. SJF
C. Round Robin
D. Priority
Answer: C. Round Robin
6. Which scheduling algorithm is normally non-preemptive?
A. FCFS
B. Round Robin
C. Preemptive Priority
D. Multilevel Feedback Queue
Answer: A. FCFS
7. Which scheduling algorithm selects the process with the shortest CPU burst?
A. FCFS
B. SJF
C. Round Robin
D. FIFO
Answer: B. SJF
8. Which of the following is a process state?
A. Ready
B. Compiled
C. Printed
D. Linked
Answer: A. Ready
9. Context switching means:
A. Changing the operating system
B. Switching from one process to another
C. Changing RAM to ROM
D. Formatting a disk
Answer: B. Switching from one process to another
10. Which mechanism is commonly used for process synchronization?
A. Semaphore
B. Compiler
C. Loader
D. Linker
Answer: A. Semaphore
11. Which is NOT a necessary condition for deadlock?
A. Mutual exclusion
B. Hold and wait
C. Circular wait
D. Time sharing
Answer: D. Time sharing
12. Banker's Algorithm is used for:
A. CPU scheduling
B. Deadlock avoidance
C. File allocation
D. Page replacement
Answer: B. Deadlock avoidance
13. Paging divides logical memory into:
A. Frames
B. Pages
C. Segments only
D. Blocks only
Answer: B. Pages
14. Physical memory is divided into:
A. Pages
B. Frames
C. Segments
D. Files
Answer: B. Frames
15. Which memory management technique eliminates external fragmentation?
A. Paging
B. Pure segmentation
C. Swapping
D. Overlay
Answer: A. Paging
16. A page fault occurs when:
A. CPU fails
B. Required page is not in main memory
C. Disk is formatted
D. Process terminates
Answer: B. Required page is not in main memory
17. Which page replacement algorithm replaces the least recently used page?
A. FIFO
B. LRU
C. FCFS
D. SJF
Answer: B. LRU
18. FIFO page replacement replaces:
A. The newest page
B. The page used most frequently
C. The oldest page
D. The smallest page
Answer: C. The oldest page
19. Thrashing is related to:
A. Excessive paging
B. CPU manufacturing
C. File compression
D. Disk formatting
Answer: A. Excessive paging
20. Virtual memory uses:
A. Only CPU registers
B. Secondary storage as an extension of memory
C. Only cache memory
D. BIOS
Answer: B. Secondary storage as an extension of memory
21. Which technique transfers data directly between an I/O device and memory?
A. DMA
B. FCFS
C. SJF
D. Paging
Answer: A. DMA
22. DMA stands for:
A. Direct Memory Access
B. Digital Memory Allocation
C. Direct Module Access
D. Dynamic Memory Allocation
Answer: A. Direct Memory Access
23. Which of the following is an IPC mechanism?
A. Shared Memory
B. Compiler
C. Loader
D. Assembler
Answer: A. Shared Memory
24. A critical section contains:
A. Code accessing shared resources
B. Only boot instructions
C. Only operating system files
D. Machine language instructions only
Answer: A. Code accessing shared resources
25. Which condition requires that only one process can use a resource at a time?
A. Mutual Exclusion
B. Circular Wait
C. Hold and Wait
D. Starvation
Answer: A. Mutual Exclusion
26. Which OS type is designed to respond within specified time constraints?
A. Batch OS
B. Real-Time OS
C. Distributed OS
D. Network OS
Answer: B. Real-Time OS
27. Which operating system technique keeps multiple programs in memory?
A. Multiprogramming
B. Formatting
C. Spooling only
D. Encryption
Answer: A. Multiprogramming
28. In a time-sharing system, CPU time is divided into:
A. Pages
B. Time slices
C. Frames
D. Segments
Answer: B. Time slices
29. Which file operation is used to retrieve data from a file?
A. Read
B. Delete
C. Close
D. Rename
Answer: A. Read
30. Which I/O method allows a device to notify the CPU that it needs attention?
A. Interrupt-driven I/O
B. Paging
C. Swapping
D. Segmentation
Answer: A. Interrupt-driven I/O
Quick Revision: Operating System One-Liners
OS → Interface between user and hardware.
Process → Program in execution.
PCB → Stores process-related information.
FCFS → First process to arrive gets CPU first.
SJF → Shortest CPU burst first.
Round Robin → Uses time quantum.
Semaphore → Synchronization mechanism.
Deadlock → Processes wait indefinitely for resources.
Banker's Algorithm → Deadlock avoidance.
Page → Unit of logical memory in paging.
Frame → Unit of physical memory in paging.
Page Fault → Required page is absent from main memory.
LRU → Replaces least recently used page.
Thrashing → Excessive paging activity.
DMA → Direct Memory Access.
IPC → Inter-Process Communication.
Critical Section → Code accessing shared resources.
Virtual Memory → Extends apparent memory using secondary storage.
Preparation Strategy for Bihar STET
For Operating System, candidates should particularly focus on process states, PCB, CPU scheduling algorithms, synchronization, semaphores, deadlock conditions, Banker's Algorithm, paging, segmentation, page replacement, virtual memory, thrashing, file systems and I/O techniques. These areas form the core of the Operating System topics listed for Bihar STET Computer Science preparation.
Candidates should also solve numerical questions based on FCFS, SJF, Round Robin, page replacement and deadlock/resource allocation, rather than preparing only theoretical definitions.
Important Topics to Revise
Operating System Basics
OS Types and Services
Process and PCB
Process States
Context Switching
CPU Scheduling
Process Synchronization
Semaphores
IPC
Deadlocks
Banker's Algorithm
Memory Management
Paging and Segmentation
Virtual Memory
Page Replacement Algorithms
Thrashing
File Systems
I/O Management
Interrupts
DMA
Note: For the latest Bihar STET 2026 application and examination information, candidates should verify details against the current BSEB notification. The 2026 notification was released on August 14, 2026, with applications reported from August 17 to August 31, 2026.
For additional Bihar technical/computer-science syllabus references, the State Board of Technical Education Bihar also publishes Computer Science and Engineering curriculum material, including Operating System concepts such as OS functions, process management, synchronization and related topics.
