🔵 UNIT – I : INTRODUCTION TO OPERATING SYSTEM
Q1. What is an Operating System?
(VVI | 5–10 Marks)
Definition
An Operating System (OS) is a system software that acts as an interface between the user and computer hardware.
It manages hardware resources and provides services to application programs.
Simple Meaning
User → OS → Hardware
Without OS, computer cannot work.
Examples
Windows, Linux, macOS, Android
Q2. Primary Functions of Operating System
(VVI | 10 Marks)
1. Process Management
- Create process
- Schedule process
- Terminate process
- Handle deadlock
2. Memory Management
- Allocate RAM
- Deallocate RAM
- Track used/free memory
3. File Management
- Create, read, write, delete files
- Organize files in directories
- Manage permissions
4. Device Management
- Control I/O devices
- Use device drivers
- Manage buffering & spooling
5. Security & Protection
- User authentication
- Access control
- Data protection
6. User Interface
- CLI (Command Line)
- GUI (Graphical Interface)
Q3. Types of Operating System
(VVI | 10 Marks)
1. Multitasking Operating System
Allows multiple programs to run at the same time.
Example:
Browser + Music Player + Code Editor
Advantage: Better CPU utilization
2. Batch Operating System
Jobs are collected and executed in batches without user interaction.
Example: Payroll system
Disadvantage: Long waiting time
3. Time Sharing Operating System
CPU time divided into small time slices and shared among users.
Example: Linux, UNIX
Feature: Fast response
4. Single User OS
One user at a time (MS-DOS)
5. Multiuser OS
Multiple users at same time (Linux server)
Q4. Operating System Services
(Important | 5 Marks)
- Program execution
- I/O operations
- File manipulation
- Communication
- Error detection
- Resource allocation
Q5. System Call
(VVI | 5 Marks)
Definition
System call is a method by which a user program requests services from the OS.
Types
- Process control
- File management
- Device management
- Communication
Examples
read(), write(), open(), fork()
Q6. System Structure of Operating System
(Important | 5–10 Marks)
Types
- Monolithic
- Layered
- Microkernel
- Modular
- Hybrid
🔵 UNIT – II : PROCESS MANAGEMENT
Q7. What is a Process?
(VVI | 5 Marks)
Definition
A process is a program in execution.
Program vs Process
| Program | Process |
|---|---|
| Static | Dynamic |
| Stored on disk | Running in memory |
Q8. Process States
(VVI | 5 Marks)
States
- New
- Ready
- Running
- Waiting
- Terminated
New → Ready → Running → Waiting
↓
Terminated
Q9. Process Control Block (PCB)
(VVI | 10 Marks)
Definition
PCB is a data structure that stores all information about a process.
Contents
- Process ID
- Process State
- Program Counter
- CPU Registers
- Memory Info
- I/O Status
- Scheduling Info
Diagram
+-----------------------+
| Process ID |
| Process State |
| Program Counter |
| CPU Registers |
| Memory Info |
| I/O Status |
| Scheduling Info |
+-----------------------+
Q10. Process Scheduling
(VVI | 5 Marks)
Definition
Process scheduling decides which process gets CPU next.
Scheduling Criteria
- CPU utilization
- Throughput
- Waiting time
- Turnaround time
- Response time
Q11. Scheduling Algorithms & FCFS
(VVI | 10 Marks)
Algorithms
- FCFS
- SJF
- Priority
- Round Robin
- Multilevel Queue
FCFS Example
| Process | Burst |
|---|---|
| P1 | 5 |
| P2 | 3 |
| P3 | 2 |
| P1 | P2 | P3 |
0 5 8 10
Advantage: Simple
Disadvantage: High waiting time
Q12. Threads
(Important | 5 Marks)
Thread is a lightweight process.
Advantages
- Faster execution
- Less memory usage
🔵 UNIT – III : SYNCHRONIZATION & DEADLOCK
Q13. Critical Section Problem
(VVI | 5 Marks)
Critical section is the part of code where shared resources are accessed.
Requirements
- Mutual exclusion
- Progress
- Bounded waiting
Q14. Semaphore
(VVI | 5 Marks)
Semaphore is a synchronization tool.
Types
- Binary semaphore
- Counting semaphore
Q15. Deadlock
(VVI | 10 Marks)
Definition
Deadlock is a situation where processes wait forever for resources held by each other.
Deadlock Characteristics
- Mutual exclusion
- Hold and wait
- No preemption
- Circular wait
Deadlock Handling Methods
- Deadlock prevention
- Deadlock avoidance
- Deadlock detection
- Recovery from deadlock
Recovery
- Kill process
- Resource preemption
🔵 UNIT – IV : MEMORY MANAGEMENT
Q16. Logical vs Physical Address Space
(VVI | 5 Marks)
| Logical Address | Physical Address |
|---|---|
| Virtual | Real |
| CPU generated | RAM location |
Q17. Swapping
(VVI | 5 Marks)
Process is moved from RAM to disk temporarily to free memory.
Q18. Paging
(VVI | 10 Marks)
Memory divided into:
- Pages (logical)
- Frames (physical)
Advantage: No external fragmentation
Q19. Segmentation
(VVI | 5 Marks)
Memory divided into logical segments:
- Code
- Data
- Stack
Q20. Virtual Memory & Demand Paging
(VVI | 10 Marks)
Allows execution of programs larger than RAM.
Pages loaded only when needed.
Q21. Page Replacement Algorithms
(VVI | 10 Marks)
- FIFO
- LRU
- Optimal
- LFU
🔵 UNIT – V : FILE & DISK MANAGEMENT
Q22. Disk Scheduling Algorithms
(VVI | 10 Marks)
- FCFS
- SSTF
- SCAN
- C-SCAN
- LOOK
Q23. File
(VVI | 5 Marks)
File is a collection of related data stored on disk.
Q24. File Allocation Methods
(VVI | 10 Marks)
- Contiguous allocation
- Linked allocation
- Indexed allocation
Q25. File Operations
(Important | 5 Marks)
- Create
- Open
- Read
- Write
- Close
- Delete
Q26. Directory Structure
(VVI | 10 Marks)
- Single level
- Two level
- Tree structure
- Acyclic graph
- General graph
✅ HOW TO USE THIS FOR EXAM
- 5 Marks: Definition + 4 points
- 10 Marks: Definition + diagram + explanation
- Draw small diagrams
- Use headings
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