Top OS Interview Questions(2021)

Top OS Interview Questions(2021)
Top OS Interview Questions(2021)


The blog covers the top 30 interview level Operating System Interview Questions. Let’s continue learning about the top Operating System Interview Questions and their answers asked by leading tech companies.

Operating System Interview Questions

Q1. What is an Operating System?


An Operating System is an interface between computer hardware and computer users. It performs tasks like memory management, file management, process management, controlling peripheral devices such as disk drives and printers, and handling input and output. 

Example: Linux Operating System, Windows Operating System, etc. 


Q2. List some of the standard services by OS?

Answer: Some of the standard services by OS are :

  1. User interface 
  2. Program execution 
  3. I/O operations 
  4. File-system manipulation 
  5. Communications 
  6. Error detection 
  7. Resource allocation 
  8. Accounting 
  9. Protection and security

Q3. What is the operating system’s primary purpose?

Answer: There are two primary purposes of an operating system(OS):

  1. It is designed to make sure that a computer system performs well by managing its computational activities.
  2. It provides an environment for the development and execution of programs.

Q4. Name some of the crucial functions of an operating system. 

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  1. Memory Management 
  2. Processor Management 
  3. Device Management 
  4. File Management 
  5. Security 
  6. Control over system performance 
  7. Job accounting 
  8. Error detecting aids 
  9. Coordination between other software and users

Q5. What are the different operating systems?


  • Batched operating systems
  • Distributed operating systems
  • Time-Sharing operating systems
  • Multiprogrammed operating systems.
  • Real-time operating systems

Q6. What is a socket in OS?

Answer: A socket is used to make connections between two applications. Endpoints of the connection are called a socket.

Q7. Explain various activities/ functions of OS?


Memory Management 

It refers to the management of Main Memory or Primary Memory, an extensive array of words, each having its address.

Main memory provides fast storage that can be accessed directly by the CPU. 

Some of its activities are:

  1. It keeps track of the main memory, i.e., what part is in use by whom and what part is not in use. 
  2. When a process requests, it allocates the memory to it. 
  3. When a process no longer needs the memory, it de-allocates the memory. 

Processor Management 

It helps the OS to decide which process gets the processor when and for how much time. 

Some of its activities are: 

  1. It keeps track of the processor and status of the process. 
  2. When a process requests, it allocates the processor (CPU) to it. 
  3. When a process no longer needs the processor, it de-allocates it.

Device Management 

An OS manages device communication via their respective drivers.

Some of its activities are:  

  1. It keeps track of all devices.  
  2. Efficiently allocates the device. 
  3. De-allocates devices. 

File Management 

A file system is usually organized into directories for easy navigation and usage. These directories may contain files and other directories.

Some of its activities are: 

  1. It keeps track of location, information, uses, status, etc. The collective facilities are often known as the file system. 
  2. Decides who gets the resources. 
  3. Allocates the resources. 
  4. De-allocates the resources.

Security − It prevents unauthorized access to programs and data. 

Control over system performance − It records delays between the request for a service and the response from the operating system. 

Job accounting − It keeps track of resources and time used by various users and jobs. 

Error detecting aids − It helps in detecting the production of dumps, traces, error messages, and other debugging and error detecting aids. 

Coordination between other software and users − It coordinates and assigns compilers, assemblers, interpreters, and other software to the multiple users of the computer systems.

Q8.What is the Batch Operating System?


It doesn’t interact with the computer directly. There is an operator which takes similar jobs having the exact requirement and groups them into batches.  

It is the responsibility of the operator to sort the jobs with similar needs. 


Q9. What are the benefits and disadvantages of a Batch Operating System?


Advantages of Batch Operating System: 

* Multiple users can share the batch systems 

* Batch system’s idle time is significantly less 

* It is easy to manage extensive work repeatedly in batch systems 

Disadvantages of Batch Operating System:  

* Batch systems are hard to debug 

* If any job fails, the other jobs will have to wait for an unknown time.

Q10. What are Time-Sharing Operating Systems?


In a time-sharing Operating System, each user gets the CPU time as they use a single system, and each task is given some time to execute so that all the tasks work smoothly. Hence, this system is 

also known as Multitasking Systems.  

The time that each task gets to execute is called quantum. After this time interval is over, the OS switches over to the next task. 


Q11. What are the benefits and disadvantages of a Time-Sharing Operating System?


Advantages of a Time-Sharing Operating System:

* Each task gets an equal opportunity 

* CPU idle time can be reduced 

 Disadvantages of Time-Sharing Operating System: 

* One must have to take care of the security and integrity of user programs and data

Q12. What is a Distributed Operating System? 


In the Distributed Operating System, various autonomous, interconnected computers communicate with each other using a shared communication network. All the independent systems possess their memory unit and CPU. So, These are also known as loosely coupled systems.  

These system’s processors differ in size and function.  

The primary benefit of working with these operating system types is that it is always possible that one user can access the files or software that are not present on his system. Still, on some other system connected within this network i.e., remote access is enabled within the connected devices. 

Q13. What are the benefits and disadvantages of a Distributed Operating System?


Benefits of Distributed Operating System: 

* Failure of one will not affect the other network communication, as all systems are independent of each other.

* Since resources are being shared, computation is high-speed and durable.

* These systems are easily scalable as many systems can be easily added to the network.

Disadvantages of Distributed Operating System: 

* Failure of the leading network will stop the entire communication

Q14. What is a Real-Time Operating System?


Real-Time Operating Systems are types of OSs that serve real-time systems.  

The time interval required to process and respond to inputs is minimal. This time interval is called response time

They are generally used when there are stringent time requirements, like missile systems, air traffic control systems, robots, etc. 

Q15. What are the two types of Real-Time Operating systems?


  1. Hard Real-Time Systems: 

These OSs are meant for applications where time constraints are stringent, and even the shortest possible delay is unacceptable.  

Example: These systems are built for saving life like automatic parachutes or airbags, which are required to be readily available in case of an accident. Virtual memory is seldom found in these systems. 

  1. Soft Real-Time Systems: 

These OSs are for applications where time-constraint is less strict.

Q16. What are the advantages and disadvantages of Real-Time OS (Operating System)?


Benefits of Real-Time Operating System: 

* Maximum Consumption: Maximum utilization of devices and system, thus more output from all the resources 

* Error Free: These types of systems are error-free. 

Disadvantages of Real-Time Operating System: 

* Complex Algorithms: The algorithms are very complex and challenging for the designer to write on.

Q17. What is a kernel in an OS?

Answer: Kernel is the core and most important part of a computer operating system that provides essential services for all parts of the OS.

Q18. What is a monolithic kernel?

Answer: A monolithic kernel in an operating system is a kernel that includes all operating system code in a single executable image.

Q19. Define a process.

Answer: An executing program in an OS is known as a process. There are two types of processes:

  1. Operating System Processes
  2. User Processes

Q20. What are the different states of a process in OS?

Answer: Different states of the process are:

  • New Process
  • Running Process
  • Waiting Process
  • Ready Process
  • Terminated Process

Q21. What is the difference between process and program?

Answer: A program while running or executing is known as a process.

Q22. What is aging in the Operating System?

Answer: Aging is a technique used to avoid starvation in the resource scheduling system.

Q23. What are the advantages of multithreaded programming in OS?

Answer: A list of advantages of multithreaded programming:

  • Enhance the responsiveness to the users.
  • Resource sharing within the process.
  • Economical
  • Completely utilize the multiprocessing architecture

Q24. What are System calls?

Answer: System calls in the operating system provide an interface to the services made available by an operating system. These calls are generally known as routines written in C and C++.

Q25. Why does an application programmer prefer programming according to an API rather than invoking actual system calls? 


Due to Program Portability, i.e., An application programmer designing a program using an API can expect her program to compile and run on any system that supports the same API. Moreover, actual system calls can often be more detailed and challenging to work with than the API available to an application programmer. 

Q26. What is the role of the System Interface?

Answer : 

The run-time support system provides a system call interface that links system calls made available by the operating system. 

It intercepts function calls in the API and invokes the necessary system calls within the operating system. 

Generally, a number is associated with each system call, and the system-call interface maintains a table indexed according to these numbers. 

The system call interface then invokes the intended system call in the operating system kernel and returns the status of the system call and any return values. ∙ The caller needs to know nothing about how the system call is implemented or during execution.

Q27. What are the different scheduling algorithms in OS?


  1. First-Come, First-Served (FCFS) Scheduling. 
  2. Shortest-Job-Next (SJN) Scheduling. 
  3. Priority Scheduling. 
  4. Shortest Remaining Time. 
  5. Round Robin(RR) Scheduling. 
  6. Multiple-Level Queues Scheduling.

Q28. Describe the objective of multiprogramming in OS.

Answer: Multiprogramming increases CPU utilization by organizing jobs (code and data) so that the CPU always has one to execute. The main objective of multiprogramming is to keep multiple positions in the main memory. If one job gets occupied with IO, CPU can be assigned to other jobs. 

Q29. Give some benefits of multithreaded programming in OS?

Answer: A thread is also known as a lightweight process. The idea is to achieve parallelism by dividing a process into multiple threads. Threads within the same process run in shared memory space

Q30.What are various types of System calls in OS?



Key Takeaways

In this blog, we enlisted the top 33 Operating System Interview questions that are highly probable to be asked in interviews. In this series of questions, we have also covered more intermediate-level questions in  Top Operating System Interview Questions Part 2. Do check them out in case you missed them.

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By: Raksha Jain