Viva Questions - Class 8 - Operating System
Viva Questions — Operating System
A complete collection of important Viva and Interview questions with detailed answers covering all major Operating System topics — from basics to advanced concepts like process management, memory management, security, and system calls.
Introduction
The Operating System (OS) is one of the most important subjects in computer science. In viva or interviews, examiners test your understanding of core OS concepts through short, focused questions.
This article covers 60+ commonly asked viva questions with clear, concise answers organized by topic. Use this as a quick revision guide before your viva or interview.
Section 1: Basics of Operating System
Q1. What is an Operating System?
An Operating System (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs and users. It acts as an interface between the user and hardware.
Q2. What are the main functions of an Operating System?
The main functions of an OS include:
- Process Management
- Memory Management
- File System Management
- Device Management
- Security and Protection
- User Interface
- Networking
Q3. Why do we need an Operating System?
We need an OS to manage hardware resources, run applications, provide security, and offer a user-friendly environment. Without an OS, communication with hardware would require machine-level instructions.
Q4. What is the difference between system software and application software?
| System Software | Application Software |
|---|---|
| Manages hardware and provides platform for apps. | Performs specific tasks for the user. |
| Examples: Windows, Linux, macOS. | Examples: MS Word, Chrome, Photoshop. |
Q5. What is a Kernel?
The Kernel is the core part of an operating system that manages system resources, communicates with hardware, and handles process, memory, and device management.
Q6. What is a Shell?
A Shell is a program that acts as an interface between the user and the kernel. It accepts user commands and passes them to the OS for execution. Examples: Bash, PowerShell, CMD.
Section 2: Types of Operating Systems
Q7. What is a Batch Operating System?
A Batch OS executes similar types of jobs in batches without user interaction. Jobs are collected, grouped, and processed sequentially.
Q8. What is a Time-Sharing OS?
A Time-Sharing OS allows multiple users to share CPU time. Each user gets a small time slice (quantum) to work interactively with the system.
Q9. What is a Single User OS?
A Single User OS supports only one user at a time. All resources are dedicated to that user. Example: MS-DOS, early Windows.
Q10. What is a Multi User OS?
A Multi User OS allows multiple users to access the system simultaneously. Example: UNIX, Linux, Windows Server.
Q11. What is a Real-Time OS? (Give examples)
A Real-Time OS (RTOS) processes data within strict time deadlines. It is used in time-critical applications.
Q12. What is a Distributed OS?
A Distributed OS manages a group of independent computers and makes them appear as a single coherent system. Example: Amoeba, Plan 9.
Q13. What is a Network Operating System?
A Network OS runs on a server and provides services like file sharing, printing, and user management to computers on a network. Example: Windows Server, Novell NetWare.
Section 3: Process Management
Q14. What is a Process?
A Process is a program in execution. It includes the program code, data, stack, and other resources needed to run.
Q15. What are the states of a process?
The main process states are:
- New – Process is being created
- Ready – Waiting for CPU allocation
- Running – Executing on the CPU
- Waiting/Blocked – Waiting for an event (I/O)
- Terminated – Execution completed
Q16. What is the difference between a process and a program?
| Program | Process |
|---|---|
| Static set of instructions stored on disk. | Program in execution in memory. |
| Passive entity. | Active entity. |
| Does not require resources. | Requires CPU, memory, and I/O resources. |
Q17. What is Context Switching?
Context Switching is the process of saving the state of a running process and loading the state of another process so the CPU can switch between them.
Q18. What is a Process Control Block (PCB)?
A PCB is a data structure maintained by the OS to store information about a process such as process ID, state, program counter, registers, memory limits, and I/O status.
Q19. What is CPU Scheduling?
CPU Scheduling is the process of deciding which process gets the CPU next. Common algorithms include FCFS, SJF, Priority Scheduling, and Round Robin.
Section 4: Memory Management
Q20. What is Memory Management?
Memory Management is the function of the OS that handles allocation and deallocation of memory to programs, ensures efficient usage, and prevents interference between processes.
Q21. What is the difference between Physical and Virtual Memory?
| Physical Memory | Virtual Memory |
|---|---|
| Actual RAM installed in the system. | Illusion of large memory using disk space. |
| Fast access. | Slower access (uses disk). |
| Limited by hardware. | Extends the size of RAM logically. |
Q22. What is Paging?
Paging is a memory management scheme that divides memory into fixed-size blocks called pages (logical) and frames (physical). It eliminates external fragmentation.
Q23. What is Segmentation?
Segmentation divides memory into variable-sized segments based on logical divisions of a program (like code, data, stack). It supports logical view of memory.
Q24. What is Demand Paging?
Demand Paging is a technique where pages are loaded into memory only when they are needed by the CPU, reducing memory usage and improving performance.
Q25. What is Thrashing?
Thrashing occurs when the OS spends more time swapping pages in and out of memory than executing processes. It severely reduces system performance.
Section 5: File System Management
Q26. What is a File System?
A File System is the method used by the OS to store, organize, retrieve, and manage files on a storage device.
Q27. What is a File?
A File is a named collection of related data stored on a storage device. It can contain text, images, programs, or any digital information.
Q28. What are the operations performed on files?
- Create
- Open
- Read
- Write
- Close
- Delete
- Rename
Q29. What is a Directory?
A Directory (also called folder) is a container that stores files and other directories. It helps organize files hierarchically.
Q30. What is the difference between file and directory?
| File | Directory |
|---|---|
| Contains data or information. | Contains files and other directories. |
| Cannot hold other files. | Organizes files hierarchically. |
Q31. What are the types of file systems?
Common file systems include FAT32, NTFS (Windows), EXT4 (Linux), APFS (macOS), and exFAT for removable drives.
Section 6: I/O and Device Management
Q32. What is Device Management?
Device Management is the OS function that controls all input/output devices, handles data transfer, and manages device drivers.
Q33. What is a Device Driver?
A Device Driver is a software program that allows the OS to communicate with hardware devices such as printers, keyboards, and disks.
Q34. What is Buffering?
Buffering is the process of temporarily storing data in memory while it is being transferred between two devices or between a device and an application. It helps handle speed differences.
Q35. What is Spooling?
Spooling (Simultaneous Peripheral Operations On-Line) stores data in a queue (buffer) for later processing. It is commonly used with printers.
Q36. What is the difference between Synchronous and Asynchronous I/O?
| Synchronous I/O | Asynchronous I/O |
|---|---|
| Process waits until I/O completes. | Process continues without waiting. |
| Blocking operation. | Non-blocking operation. |
Q37. What is DMA (Direct Memory Access)?
DMA is a feature that allows devices to transfer data directly to/from memory without CPU intervention, improving performance and freeing the CPU for other tasks.
Section 7: Security and Protection
Q38. What is Security in OS?
Security in OS involves protecting data, resources, and the system from unauthorized access, malware, and external threats.
Q39. What is the difference between Authentication and Authorization?
| Authentication | Authorization |
|---|---|
| Verifies user identity. | Determines user access rights. |
| Example: Login with password. | Example: Access to admin panel. |
Q40. What is Access Control?
Access Control is a security mechanism that restricts users from accessing resources they are not authorized to use.
Q41. What are the different access control methods?
- DAC – Discretionary Access Control
- MAC – Mandatory Access Control
- RBAC – Role-Based Access Control
- ABAC – Attribute-Based Access Control
Q42. What is the need for protection in OS?
Protection is essential to prevent unauthorized access, data corruption, malware attacks, and misuse of system resources. It ensures data integrity, privacy, and system stability.
Section 8: System Calls and Services
Q43. What is a System Call?
A System Call is a programmatic way for user applications to request services from the operating system kernel — such as file access, memory allocation, or process creation.
Q44. What are the types of System Calls?
- Process Control (fork, exec, exit)
- File Management (open, read, write, close)
- Device Management (ioctl, read, write)
- Information Maintenance (getpid, alarm)
- Communication (pipe, shmget, send, recv)
Q45. What is the difference between a System Call and a Library Function?
| System Call | Library Function |
|---|---|
| Direct request to the kernel. | Runs entirely in user space. |
| Slower due to mode switching. | Faster execution. |
| Example: open(), fork() | Example: printf(), strlen() |
Q46. Give some examples of System Calls.
fork(), exec(), wait(),
open(), read(), write(),
close(), getpid(), kill().
Q47. What is an Interrupt?
An Interrupt is a signal sent to the CPU by hardware or software indicating an event that needs immediate attention. It temporarily stops the current program to run an interrupt handler.
Section 9: Multitasking and Multiuser
Q48. What is Multitasking?
Multitasking is the ability of an OS to run multiple programs concurrently by sharing CPU time through time-slicing.
Q49. What is the difference between Preemptive and Non-Preemptive Multitasking?
| Preemptive | Non-Preemptive |
|---|---|
| OS forcefully switches tasks based on priority/time. | Task voluntarily gives up CPU. |
| Better responsiveness. | Simpler but can cause delays. |
| Example: Windows, Linux, macOS. | Example: Older Windows 3.x, Mac OS 9. |
Q50. What is a Multiuser System?
A Multiuser System allows multiple users to access the same computer simultaneously with proper resource sharing and security.
Q51. What is the difference between Multitasking and Multiuser System?
| Multitasking | Multiuser |
|---|---|
| Focuses on running multiple tasks. | Focuses on serving multiple users. |
| Time-slicing between programs. | Resource sharing between users. |
Section 10: Other Important Questions
Q52. What is Booting?
Booting is the process of starting a computer and loading the operating system into memory when the system is powered on.
Q53. What are the different types of Booting?
- Cold Boot (Hard Boot): Starting the computer from a completely powered-off state.
- Warm Boot (Soft Boot): Restarting the computer without turning off power.
Q54. What is Deadlock? How can it be prevented?
Deadlock is a situation where two or more processes are waiting for each other's resources indefinitely.
Deadlock can be prevented by breaking any of the four conditions:
- Mutual Exclusion
- Hold and Wait
- No Preemption
- Circular Wait
Q55. What is the difference between 32-bit and 64-bit OS?
| 32-bit OS | 64-bit OS |
|---|---|
| Supports up to 4 GB RAM. | Supports much larger RAM (16 EB theoretically). |
| Slower performance. | Faster and more efficient. |
| Runs 32-bit applications only. | Runs both 32-bit and 64-bit applications. |
Q56. What is the role of OS in mobile phones?
A Mobile OS manages hardware resources, applications, touch interface, connectivity, battery, and security on smartphones and tablets. Examples: Android, iOS, HarmonyOS.
Q57. What is the difference between Kernel Mode and User Mode?
| Kernel Mode | User Mode |
|---|---|
| Has full access to hardware and system resources. | Restricted access; runs user applications. |
| Executes privileged instructions. | Cannot execute privileged instructions. |
| Example: OS core, drivers. | Example: MS Word, Chrome. |
Commonly Asked Follow-Up Questions
Examiners often ask follow-up questions to test your depth of understanding. Be prepared for questions like:
Follow-Up Question Types
- "Can you explain with an example?"
- "What happens if …?"
- "How does it work internally?"
- "What are the advantages and disadvantages?"
- "How is it different from other systems?"
- "Which is better and why?"
- "Can you draw a diagram to explain?"
Key Terms to Remember
These are the most important OS terms every student should know before a viva or interview.
| Term | Meaning |
|---|---|
| Kernel | Core of the operating system. |
| Shell | Interface between user and kernel. |
| Process | Program in execution. |
| Thread | Lightweight unit of a process. |
| PCB | Process Control Block — stores process info. |
| Scheduling | Assigning CPU to processes. |
| Paging | Memory divided into fixed-size pages. |
| Segmentation | Memory divided into variable-sized segments. |
| Deadlock | Processes waiting on each other forever. |
| System Call | Request from a program to the OS kernel. |
| I/O | Input/Output operations. |
| Spooling | Data queued for a device (e.g. printer). |
| Virtual Memory | Uses disk to extend RAM. |
| File System | Method to organize and store files. |
| Interrupt | Signal that requires CPU attention. |
Tips for Viva
Golden Rules for Viva Success
- Answer confidently and clearly.
- Use neat diagrams wherever needed.
- Give real-life examples to explain concepts.
- If you don't know, be honest — but try to explain your understanding.
- Practice regularly and revise key concepts often.
- Maintain eye contact and speak politely.
- Stay calm even if the question is tough.
- Rephrase the question if you need time to think.
- Use technical terms correctly.
- End answers with a brief example whenever possible.
Final Note
Understanding Operating System concepts with examples
and practical knowledge is the key to cracking any viva or
technical interview. Practice, understand, apply, and succeed!
Best of Luck — Keep Learning and Keep Growing!
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