Operating System Tutorial

Operating System Tutorial Types of Operating System Evolution of Operating System Functions of Operating System Operating System Properties Operating System Services Components of Operating System Needs of the Operating System

Operating Systems

Linux Operating System Unix Operating System Ubuntu Operating System Chrome Operating Systems Fedora Operating System MAC Operating System MS Windows Operating System Solaris Operating System Cooperative Operating System CorelDRAW Operating System CentOS FreeBSD Operating Systems Batch Operating System MS-DOS Operating System Commercial Mobile Operating Systems


Difference Between Multi-programming and Multitasking Difference between C-LOOK and C-SCAN Difference between Rotational Latency and Disk Assess Time Trap vs Interrupt Difference between C-SCAN and SSTF Difference between SCAN and FCFS Difference between Seek Time and Disk Access Time Difference between SSTF and LOOK Difference between Process and Program in the Operating System Difference between Protection and Security in Operating System

How To

How to implement Monitors using Semaphores How to Install a Different Operating System on a PC


What is Kernel and Types of Kernel What is DOS Operating System What is Thread and Types of Thread What is Process Scheduler and Process Queue What is Context Switching What is CPU Scheduling What is Producer-Consumer Problem What is Semaphore in Operating System Monitors in Operating System What is Deadlock What is Paging and Segmentation What is Demand Paging What is Virtual Memory What is a Long term Scheduler What is Page Replacement in Operating System What is BSR Mode What is Convoy Effect What is Job Sequencing in Operating System Why is it critical for the Scheduler to distinguish between I/O-bound and CPU-bound programs Why is there a Need for an Operating System


Process Management Process State Scheduling Algorithm FCFS (First-come-First-Serve) Scheduling SJF (Shortest Job First) Scheduling Round-Robin CPU Scheduling Priority Based Scheduling HRRN (Highest Response Ratio Next) Scheduling Process Synchronization Lock Variable Mechanism TSL Mechanism Turn Variable Mechanism Interested Variable Mechanism Deadlock Avoidance Strategies for Handling Deadlock Deadlock Prevention Deadlock Detection and Recovery Resource Allocation Graph Banker’s Algorithm in Operating System Fixed Partitioning and Dynamic Partitioning Partitioning Algorithms Disk Scheduling Algorithms FCFS and SSTF Disk Scheduling Algorithm SCAN and C-SCAN Disk Scheduling Algorithm Look and C-Look Disk Scheduling Algorithm File in Operating System File Access Methods in Operating System File Allocation Method Directory Structure in Operating System N-Step-SCAN Disk Scheduling Feedback Queue in Operating System Contiguous Memory Allocation in Operating System Real-time Operating System Starvation in Operating System Thrashing in Operating System 5 Goals of Operating System Advantages of Operating System Advantages of UNIX Operating System Bit Vector in Operating System Booting Process in Operating System Can a Computer Run Without the Operating System Dining Philosophers Problem in Operating System Free Space Management in Operating System Inter Process Communication in Operating System Swapping in Operating System Memory Management in Operating System Multiprogramming Operating System Multitasking Operating Systems Multi-user Operating Systems Non-Contiguous Memory Allocation in Operating System Page Table in Operating System Process Scheduling in Operating System Segmentation in Operating System Simple Structure in Operating System Single-User Operating System Two Phase Locking Protocol Advantages and Disadvantages of Operating System Arithmetic operations in binary number system Assemblers in the operating system Bakery Algorithm in Operating System Benefits of Ubuntu Operating System CPU Scheduling Criteria in Operating System Critical Section in Operating System Device Management in Operating System Linux Scheduler in Operating System Long Term Scheduler in Operating System Mutex in Operating System Operating System Failure Peterson's Solution in Operating System Privileged and Non-Privileged Instructions in Operating System Swapping in Operating System Types of Operating System Zombie and Orphan Process in Operating System 62-bit operating system Advantages and Disadvantages of Batch Operating System Boot Block and Bad Block in Operating System Contiguous and Non - Contiguous Memory Allocation in Operating System Control and Distribution Systems in Operations Management Control Program in Operating System Convergent Technologies in Operating System Convoy Effect in Operating System Copy Operating Systems to SSD Core Components of Operating System Core of UNIX Operating System Correct Value to return to the Operating System Corrupted Operating System Cos is Smart Card Operating System Cosmos Operating Systems Examples Generation of Operating System Hardware Solution in Operating System Process Control Block in Operating System Function of Kernel in Operating System Operating System Layers History of Debian Operating Systems Branches and Architecture of Debian Operating Systems Features and Packages of Debian Operating Systems Installation of Operating System on a New PC Organizational Structure and Development in Debian Operating Systems User Interface in Operating System Types Of Memory in OS Operating System in Nokia Multilevel Paging in OS Memory Mapping Techniques in OS Memory Layout of a Process in Operating System Hardware Protection in Operating System Functions of File Management in Operating System Core of Linux Operating System Cache Replacement Policy in Operating System Cache Line and Cache Size in Operating System What is Memory Mapping? Difference Between Network Operating System And Distributed Operating System What is the difference between a Hard link and a Soft Link? Principles of Preemptive Scheduling Process Scheduling Algorithms What is NOS? What is the Interrupt I/O Process? What is Time Sharing OS What is process termination? What is Time-Sharing Operating System What is Batch File File system manipulation What is Message-passing Technique in OS Logical Clock in Distributed System

Virtual Memory in Operating System

What is Virtual Memory

Virtual Memory is a storage scheme in which the users have an illusion that users have a significant amount of Main Memory. We can perform this by taking a section of Secondary storage as the Main Memory.

With the help of virtual memory, we can load or store the large size processes than the available memory.

In other words, Virtual Memory is defined as an area in which the programs of large size are able to store themselves in the form of pages.

 Virtual Memory is helpful in the scenario where the users have a small amount of physical memory. With the help of demand paging and demand segmentation, virtual memory is implemented.

How Virtual Memory Works

In today’s scenario, the concept of Virtual Memory is quite common. Virtual Memory is used when pages need to be loaded in the Main memory, but there is no availability of memory for the pages.

So, in this situation, instead of avoiding pages to enter into the Main Memory, the operating system finds the space for RAM (Random Access Memory) which are slightest used in the current time or, which are not referenced into the secondary storage for the purpose of creating the space for the new pages into the Main memory.

Because all this mechanism is done automatically, so this makes the computer with a more amount of RAM (Random Access Memory).

Benefits of Virtual Memory

The benefits of virtual memory are:

  1. With the help of Virtual Memory, we can execute the number of processes at once.
  2. It is helpful to fit the various programs into a smaller program.
  3. With the help of Virtual Memory, we can run multiple applications at a time.
  4. In this, a similar code or data can be shared with the memory.
  5. Code or data must be read from the disk when needed.
  6. Virtual Memory is useful in the implementation of a multiprogramming environment.
  7. The processes are kept in the main memory. Due to this, the CPU is used effectively.
  8. In Virtual Memory, the user is able to run a large-size application in the less RAM.
  9. In Virtual Memory, no requirement to purchase or buy more RAMs memory.
  10. We can place the code anywhere in the physical memory without any need for relocation.

Drawbacks of Virtual Memory

The drawbacks of virtual memory are:

  1. Virtual Memory can reduce system stability.
  2. Virtual memory does not provide the same performance as RAM.
  3. When the system use virtual memory, then the application may run slower.
  4. To switch between the applications, Virtual Memory requires more time.
  5. If we use Virtual Memory, then we don’t have more hard disk space for its use.

Snapshot of a Virtual Memory Management System

What is Virtual Memory

Suppose we have two processes, which are process P1 and the process P2. Process P1 and P2 comprises of four pages. Each page size is 1 KB. There are eight frames that are present in the Main Memory, and the size of each frame is 1 KB. The operating system is residing in the first 2 partitions. The first page of the process P1 is stored in the third partition. In the memory, the other frames are also occupied with the different process pages.

The size of each page table is 1KB. So, we can fit each of these in one frame. We can see in the above diagram; the page table consists of several types of information.

There is a register contained in the CPU that includes the base address of the page table. The base address of the process P1 is 5, and the base address of the process P2 is 7. To access the actual corresponding entry, the base address of the page table is added to the page number of the logical address.