Top 30 OS Interview Questions and Answers for Freshers

Do you also want to become an operating system specialist, and are engaged in preparing for the interview for OS? Or are you a student, who wants to strengthen the concept of your operating system a lot, and want to become better at it?

Whether you are either of these two, today you have come to the right place, where we are going to know about some such topics related to the operating system, which are usually asked in interviews or any viva.

Here, you will get the most accurate questions which are generally asked in every interview as well as in big companies, which will strengthen your preparation even more. And also with each question, its answer is also given so that the preparation time can be saved.

This article will go a long way in clearing your operating system skills and getting your confidence back and ready for any job. At the same time, it will also be of great help to those students who want to increase their knowledge in this subject further.

So let us now know, about similar questions which experts and teachers in this subject ask a lot –

What is an Operating System?

An operating system is a type of software program that allows computer hardware to communicate with and operate on computer software. Also, it is the most important part of a computer system, and without it, the computer is just like a box without any work.

What is the primary purpose of the operating system?

An operating system has two main purposes, which are –

  • Operating systems are designed to ensure that a computer system performs well by managing its computational activities.
  • It also provides an environment for the development and execution of computer programs.

What are the types of operating systems?

There are many types of operating systems, such as –

  • Batched Operating System
  • Real-time operating system
  • Timesharing Operating System
  • Multi-programmed operating system
  • Distributed Operating System

What is called a real-time system?

A real-time system is used when rigid-time requirements are placed on the operation of a processor. In addition, it also includes well-defined and fixed time constraints.

What is Kernel?

Kernel is the basic and most important part of a computer operating system, which provides basic services for all parts of the operating system (OS).

What is called a monolithic kernel?
It is a type of kernel, in which all the operating system code is included in a single executable image.

What is Micro Kernel?
It is a kind of kernel, which runs services affecting the minimum performance i.e. minimum performance for the operating system. And in a micro kernel operating system, all other operations are done by the processor itself.

What is Macro Kernel?
It is a combination of the micro and monolithic kernels.

What does process mean?
An executing program itself is called a process. It is of two types –

Operating System Processes
User Processes

What are the different states of a process?
It has different states –

New Process
Running Process
Waiting Process
Ready Process
Terminated Process
What is the concept of Reentrancy?
This is a very useful memory saving method for multi-programmed time-sharing systems. Also, it provides a kind of functionality, so that more than one user can share a single copy of any one program with each other during any period. It has two major aspects, which are –

Program code can modify itself.
Local data should be stored separately for each user process.
What is the advantage of multiprocessor system?
By using this, as our processors will increase, we will get more throughput as well.
Along with this, our cost will also come down significantly by using it, because resources are shared in it.
Its use also increases the overall reliability significantly. e.t.c.
What is the use of paging in operating system?
Paging is used to correct the problem of external fragmentation occurring in the operating system. This technology ensures that the data you need is available to you as quickly as possible.

What is the concept of Demand paging?
Demand paging specifies that if an area of ​​memory is not currently being used, it is converted to disk to make room for what an application needs.

What is Virtual Memory?
Virtual memory is a very useful memory management technique, which enables processes to be executed outside the memory. This technique is especially used when an executing program cannot fit into the physical memory of the computer.

What is called Thrashing?
Thrashing is a phenomenon occurring in a virtual memory scheme, when the processor spends most of its time swapping pages instead of executing instructions given by the computer.

What is Deadlock?
Deadlock an operating system

There is a specific type of situation in which two processes are waiting for each other to complete so that they can start. But this situation becomes the reason for both the processes to get stuck at the same place. As a result, neither of the two processes can be started.

What are the necessary conditions to get the deadlock?
There are four essential conditions to achieve any one deadlock, which are –

Mutual Exclusion – In this, at least one resource should be kept in non-sharable mode. If another process requests this resource, then that process must wait for the resource to be released.
Hold and Wait – A process must simultaneously have at least one resource, and it must wait for at least one other resource, which is currently being used by another process.
No preemption – Once a process has got hold of a resource (i.e. once its request has been granted), that resource cannot be taken from that process until the process itself has acquired that resource. Do not release
Circular Wait – Specifies that the processes in the system form a circular list or a chain, where each process in the chain is waiting for a resource held by the next process in the chain. Here a set of Processes {P0, P1, P2, . , ., PN } must exist such that every P[ i ] is waiting for P[ (i + 1 )% (N + 1)] .
What is FCFS?
FCFS stands for “First Come, First Served”, which is the principle of first come, first served. It is a type of scheduling algorithm. In this scheme, if a process requests the CPU first, it is allocated to the CPU first. And its implementation is managed by FIFO queue.

What is SMP?
SMP stands for “Symmetric MultiProcessing”, and is the most common type of multiple processor system. Each processor in SMP runs an identical copy of the operating system, and these copies can also communicate with each other when required.

What is RAID in Operating System?
RAID stands for “Redundant Array of Independent Disks”. It is used to store redundant data unnecessarily, in order to improve the overall performance of the system.

What are the fire levels of RAID?
It has different levels –

RAID 0 – Striped Disk Array without fault tolerance
RAID 1 – Mirroring and Duplexing
RAID 2 – Memory-style error-correcting codes
RAID 3 – Bit-interleaved Parity
RAID 4 – Block-interleaved Parity
RAID 5 – Block-interleaved distributed Parity
RAID 6 – P+Q Redundancy
What is Banker’s algorithm?
Banker’s algorithm is used to avoid deadlock. And it’s one of the good deadlock-avoidance methods. It is named as Banker’s algorithm on the banking system, where the bank never allocates its available cash in such a way that the needs of all its customers are not met. And in the same way, memory is allocated correctly in the CPU too, so that no process can lack it.

What is Fragmentation?
Fragmentation is a phenomenon of memory wastage. And due to inefficient use of space in it, it reduces the capacity and performance of the system.

How many types of fragmentation are there in Operating System?
There are two types of fragmentation –

Internal fragmentation – This occurs when we deal with systems that have fixed-size allocation units.
External fragmentation – This occurs when we deal with systems that have variable-size allocation units.
What is Spooling?
Spooling is a process in which data is temporarily gathered to be used and executed by a device, program or a system. And its work is related to printing. When different applications send an output to the printer at the same time, spooling puts all these jobs in a disk file and queues them according to the printer.

What is a Semaphore?
A semaphore is a type of protected variable or abstract data type, which is used to lock the resources that are being used. And the value of a semaphore indicates the position of a common resource. There are two types of Semaphore –

Binary semaphores
Counting semaphores
What is Belady’s Anomaly?
Belady’s Anomaly is also known as FIFO anomaly. Typically, by increasing the number of frames allocated to processing virtual memory, the execution of that process is faster, as it now has fewer page faults. But sometimes, the opposite happens, that is, the execution time increases even if more frames are allocated for the process. And this is called Belady’s Anomaly. And this is true for some page reference patterns.

What is called starvation in Operating System?
Startation is a resource management problem. In this problem, a waiting process requires a considerable amount of time.

are not available, because resources are being allocated to some other process ie processes.

What is aging in Operating System?
Aging is a technique used to avoid starvation in resource scheduling systems.

What are the advantages of multithreaded programming?
There are many benefits of using multithreaded programming, such as –

In this, there is sharing of resources among the processes.
It enhances accountability for the users.
It fully utilizes the multiprocessing architecture.
At the same time, it is also quite economical.
What is Overlays?
There are methods of overlays, which make a process larger than the amount of memory allocated to it. Also overlays ensure that only important instructions and data are kept in memory at any given time.

When does thrashing happen in the operating system?
Thrashing specifies an example of high paging activity. And this happens when it is spending more time paging than executing processes.

FAQ (Frequently Asked Questions)
When was the first operating system created?
The first operating system sold with computers was invented by IBM in 1964 to power its mainframe computers. This operating system was known as IBM Systems/360.

What is socket?
Socket is used to make connection between two applications. And the endpoint of a connection ie the endpoints are called socket.

What is the difference between Process and Program?
When a program is run or executed, then it is called process.

What is a thread called?
Thread is a basic unit of CPU utilization. It contains thread ID, program counter, register set and stack.

What is the full form of FCFS?
FCFS stands for “First Come, First Served”.

What is the difference between logical and physical address space?
The logical address space specifies the address, which is generated by the CPU. The same, physical address space specifies the address, which is seen by the memory unit.

What is the difference between internal and external commands?
Internal commands are built-in part of an operating system, whereas external commands are separate file programs, which are stored in a separate folder or directory.

What is Binary Semaphore?
Binary Semaphore takes only 0 and 1 as values, and is used to implement mutual exclusion and synchronize concurrent processes.

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