Consider reading a file from disk for a process: Determine device holding file Translate name to devise representation Physically read data from disk into the buffer Make data available to requesting process Return control to process The following steps have described the lifecycle of a blocking read request: A process issues a blocking read() system […]
Category: Operating System
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Kernel I/O Subsystem
The kernel provides many services related to I/O. Several services (i.e. scheduling, buffering, caching, spooling, device reservation and error handling) are provided by the kernel’s I/O subsystem and build on the hardware and device driver infrastructure. I/O Scheduling: It is used to schedule a set of I/O requests that means to determine a good order […]
Disk Management The operating system is responsible for several aspects of disk management. Disk Formatting A new magnetic disk is a blank slate. It is just platters of a magnetic recording material. Before a disk can store data, it must be divided into sectors that the disk controller can read and write. This process is […]
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Hard Disk Structure
Disk Structure The magnetic disk provides the bulk of secondary storage for modern computer systems. Each disk platter has a flat circular shape, like a CD. Common platter diameters range from 1.8 to 5.25 inches. The two surfaces of a platter are covered with magnetic material. We store information by recording it magnetically on the […]
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File Directory Structure
A directory is an object that contains the names of file system objects. The file system allows users to organize files and other file system objects through the use of directories. The structure created by the placement of names in directories can take a number of forms: Single-level tree, Two-level tree, multi-level tree or cyclic […]
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File Access Method
File Access Methods When a file is used, this information must be accessed and read into computer memory. The information in the file can be accessed in several ways. There are two major access methods as follows:- Sequential Access: Information in the file is processed in order, one record after the other. A read operation […]
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Types of file
Types of File:- Types of the file, The files are classified into different categories as follows: The name is split into two parts-a names and an extension, The system uses the extension to indicate the type of the file and the type of operations that can be done on that file. Access Methods:- When a […]
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File Operation
The operating system can provide system calls to create, write, read, reposition, delete, and truncate files. The file operations are described as followed: File Operation:- Creating a file: Two steps are necessary to create a file. First, space in the file system must be found for the file. Second, an entry for the new file […]
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File System Interface
File System:- The file system provides the mechanism for online storage of and access to both data and programs of the operating system and all the users of the computer system. The file system consists of two distinct parts: a collection of files, each storing related data, and a directory structure, which organizes and provides […]
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Thrashing
The system spends most of its time shuttling pages between main memory and secondary memory due to frequent page faults. This behavior is known as thrashing. A process is thrashing if it is spending more time paging than executing. This leads to: low CPU utilization and the operating system thinks that it needs to increase […]
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Allocation Of Frames
Frame When a page fault occurs, there is a free frame available to store a new page into a frame. While the page swap is taking place, a replacement can be selected, which is written to the disk as the user process continues to execute. The operating system allocates all its buffer and tablespace from […]
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Page Replacement Algorithm
Page Replacement Algorithm:- The page replacement is a mechanism that loads a page from disc to memory when a page of memory needs to be allocated. Page replacement can be described as follows: Find the location of the desired page on the disk. Find a free frame: If there is a free frame, use it. […]
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Demand Paging
Demand Paging A demand-paging system is similar to a paging system with swapping. Generally, Processes reside on secondary memory (which is usually a disk). When we want to execute a process, we swap it into memory. Rather than swapping the entire process into memory, it swaps the required page. This can be done by a […]
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Virtual Memory
Virtual Memory Virtual memory in Operating System is a technique that allows the execution of processes that may not be completely in memory. The only part of the program needs to be in memory for execution. It means that Logical address space can be much larger than physical address space. Virtual memory allows processes to […]
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Segmentation
Segmentation:- Segmentation is a memory-management scheme that supports the user view of memory. A program is a collection of segments. A segment is a logical unit such as the main program, procedure, function, method, object, local variables, global variables, common block, stack, symbol table, arrays, etc. A logical-address space is a collection of segments. Each […]