Operating System Tutorial

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Operating Systems

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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

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

Contiguous Memory Allocation in Operating System

Memory is a place where data, facts, figures, and information are stored for temporary or permanent access the data in future, which is also considered as the storage place.

Allocation of memory refers to the concept of providing certain memory or storage space to certain data; for example, if we enter the Z alphabet from the keyboard, the system will allocate memory for Z, and if we assign 99 value to Z, the system will store 99 at the Z location ( Here, Z is considered as a location in memory for human understanding only, but inside the system, there is no such location named as Z. Inside the system Z is also stored at the certain address which is a set of binary numbers. )

Memory Management Strategies:

There are two types of memory management strategies, which are given below:

1) Contiguous Memory Allocation

  1.  Fixed Partition
  2.  Variable/Dynamic Partition

2) Non-Contiguous Memory Allocation

Contiguous Memory Allocation: It refers to the concept of providing continuous memory/space to similar types of processes, irrespective of the number of processes. For example, if a process contains four blocks named as Zi, Zii, Ziii, and Ziv, the system will try to allocate/ provide a contiguous address to the entire block of that process in the RAM. It will allocate Zi next to Zii and Zii next to Ziii, and so on.

Contiguous memory allocation is one of the most important strategies for memory management. In this method, the memory is either branched in fixed sizes and slots or randomly branched as per the size and space required by the file. One single process holds an individual (entire) partition of contiguous memory, and because of this feature, it becomes very easy to access any random data from its process.   

  1. Fixed Partition: Fixed partition of memory is associated with the concept of contiguous memory allocation. This method allows us to divide the memory into certain fixed parts or make various slots of the same size. Nowadays, this method is no longer used because there are various evolved and modern forms of this method, which are way better and improved methods than fixed partitioning. Some of them are paging, segmentation, multilevel paging, inverted paging, etc. (the fixed method is the basis of all mentioned methods, all of these methods are the developed and improved versions of the static method). The Fixed Partitioning method was used in the 20th century around 1960. It was mainly used in the main frames or for big servers. 
  2. Dynamic Partition: Dynamic/ Variable partition of memory is associated with the concept of contiguous memory allocation. This method does not allow the partition of memory into fixed parts. As per the name suggests, it is dynamic in nature, and we cannot divide the memory into slots. In this method, we directly allocate the memory as per need depending on the file size or process.

Advantages of Contiguous Memory Allocation

There are certain advantages of allocating the memory contiguously, which are as follows:

  1. Implementation using contiguous memory allocation becomes very easy as compared to other methods used for memory management. In dynamic memory allocation, we use pointers to store the addresses, and indexes are also required. In contiguous allocation, there is no need for an index, no need for a pointer. We can put the data, and it will allocate memories as per length of the file and make it easy to implement.
  2. One of the advantages of contiguous memory allocation is that we can directly access any file from a disk. It takes a minimum to seek time, as there is no need to change track to access the data in the same file. We can access any random file from the track with the minimum time required.
    It has a magnificent reading performance.

Disadvantages of Contiguous Memory Allocation:

  1. One of the major disadvantages of contiguous memory allocation is external fragmentation. External fragmentation refers to the situation where there is the availability of memory in the system. Still, we cannot store any data or use that memory due to contiguous memory allocation.  
Contiguous Memory Allocation in Operating System
  • While using contiguous memory allocation, it is really difficult to edit and expand files. We can only add more data to the file if there is enough contiguous space available on the disk. We cannot add more data to a file if contiguous space is not available, hence cannot expand the file later.
  • Internal fragmentation is also considered as one of the disadvantages of contiguous memory allocation. It is a huge problem and is not only associated with contiguous memory allocation. It is a situation where a file uses less space for storage than the available space, and the remaining memory is wasted.