Operating System Tutorial

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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

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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

Contiguous and Non - Contiguous Memory Allocation in Operating System

A large collection of bytes is referred to as memory, and memory allocation is the process of allocating space to computer programmes. Contiguous and non-contiguous memory allocation is the two primary forms.

The tasks can be finished in a single memory region thanks to contiguous memory allocation. Non-contiguous memory allocation, on the other hand, distributes the procedure throughout several memory locations in various memory sections.

Contiguous Memory Allocation:

The mechanism of memory allocation is what it is. A single continuous piece of memory blocks is given when a process requests memory, depending on the needs of the process.

The task is finished by creating fixed-sized memory partitions and designating a single process to each partition. However, it will restrict the amount of multiprogramming to the number of done fixed partitions in memory.

Internal fragmentation is a side effect of this allocation. For instance, let's say the demand for a process's fixed-sized memory block is a little bit more than the block's size. In that situation, internal fragmentation is the term used to describe the remaining memory space in the block.

A partition becomes available for use by another process when a process within it has completed.

In the variable partitioning scheme, the OS keeps track of a table that lists the memory partitions that are free and used by processes. Allocating memory in contiguous blocks reduces address translation overheads, accelerating process execution.


  1. How many memory blocks are still available influences how much additional memory may be allocated to processes, and this information is easy to keep track of.
  2. Due to the ability to read the entire file from the disc in a single task, contiguous memory allocation has good read performance.
  3. It's easy to set up and works well to use the contiguous allotment.


  1. Because every new file may be written to the end of the disk after the previous one, fragmentation is not a problem.
  2. It must be aware of the final size of the file before creating it in order to choose the proper hole size.
  3. It would be essential to compress or repurpose the extra space in the holes once the disc is fully utilised.

Non - Contiguous Allocation:

Depending on its needs, it enables a process to obtain several memory blocks in different parts of memory. Because it makes use of the memory gaps left by internal and external fragmentation, non-contiguous memory allocation also decreases memory waste brought on by internal and external fragmentation.

Paging and segmentation are the two techniques for separating a process' physical address space. Blocks (pages or segments) of the process are split up into non-contiguous memory allocations, which are then distributed throughout various memory spaces according to the amount of available memory.

Although non-contiguous memory allocation can save wasted memory, it also adds to the costs associated with address translation. The memory execution is hindered because address translation takes time when the process pieces are stored in different places in memory.


  1. Although it provides the benefit of lessening memory waste, the address translation results in an increase in overhead.
  2. Due to the time required for address translation, it slows down memory execution.


  1. The drawback of this memory allocation is that it requires lengthy traversals of other nodes in order to access them because pointers are needed to get there.

Differences between Contiguous Memory Allocation and Non – Contiguous Memory Allocation:

  1. The process is given a single memory contiguous block as part of the contiguous memory allocation. Contrarily, a non-contiguous allocation divides the task into numerous blocks and stores them in various memory address spaces.
  2. A table indicating which partitions are available and being used by the process must be kept by the operating system in contiguous memory allocation. The base address of each process block that is placed in memory space is preserved in a table for each process in non-contiguous memory allocation, in contrast.
  3. Due to the process' storage in contiguous memory space and contiguous memory allocation, there is no execution-related overhead associated with address translation. In contrast, since the process blocks are dispersed throughout the memory space when memory is allocated in a non-contiguous manner, there is an additional burden associated with address translation during the execution of the process.
  4. Contiguous memory allocation can be better managed by the operating system. The Non-Contiguous Memory Allocation, on the other hand, is challenging for the Operating System to control.
  5. Contiguous Memory Allocation allows for speedier processing because the entire process is contained within a single sequential block. In contrast, because the process is running in multiple locations throughout the memory, the execution of its non-contiguous memory allocation is slowed down.
  6. Two memory allocations are included in a contiguous memory allocation: a single partition and a multi-partition. Paging and segmentation, on the other hand, are part of the non-contiguous memory allocation.
  7. Fragmentation in the contiguous memory allocation happens both internally and externally. The opposite is true when memory is allocated in a non-contiguous manner.
  8. In the contiguous memory allocation, swapped-in processes are put in the beginning space. Those processes that are swapped in during a non-contiguous memory allocation, however, can be set up anywhere in memory.
  9. Only one memory contiguous block is allotted to the process via contiguous memory. The process is divided up into a number of blocks that are each given their own memory address space thanks to non-contiguous memory.
  10.  Execution times for contiguous memory are significantly faster than those for non - contiguous memory allocation. Non- contiguous memory allocation and execution are slower than contiguous memory allocation and execution.
  11.  Because the process is maintained in contiguous memory space in a contiguous memory allocation, there is no overhead associated with address translation during execution. Because the process blocks are dispersed throughout the memory space, there is an overhead of address translation when a process is being executed.
  12.  Most of the time, the operating system keeps a database that lists all of the contiguous memory allocation's available and occupied partitions. Each process in the non-contiguous memory allocation is required to maintain a table that principally provides the base addresses that the memory has obtained for each block.