Operating System File System for Windows

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1. Introduction

• File System Structure

2. File System Implementation

• Design

• Implementation

• File System Mounting

3. Directory Implementation

• Linear List

• Hash Table

4. Allocation Methods

• Contiguous Allocation

• Linked Allocation

• Indexed Allocation

5. Free -Space Management

6. Efficiency and Performance

7. Recovery

8. Example: WAFL File Systems


The file system is the most visible aspect of an operating system. It provides the mechanism for online storage of and access to both data and programs of the operating system and users of the computer system that it must be able to hold large amount of data, permanently. The file system resides permanently on secondary storage, which has the main requirement.

The file system consists of two distinct parts:

• A collection of files, each storing related data, and a directory structure, which organizes and provides information about all the files in the system.

• Some file system have a third part, partitions, which are used to separate physically or logically collections of large collection of directories.

In this I considered various aspects of files, and the variety of directory structures. I also discuss ways to handle file system their efficiency and performance and some examples related to file systems.


Computers can store information on several different storage media, such as magnetic tapes, and optical disks. So that the computer system will be convenient to use, the operating system provides a uniform logical view of information storage. The operating system abstracts from the physical properties of its storage devices to define a logical storage unit, the file. Files are mapped, by the operating system, onto physical devices.

- These storage devices are usually nonvolatile, so the contents are persistent through power failures and system reboots.

A file is a named collection of related information that is recorded on secondary storage. A file is the smallest allotment of secondary storage; that is, data cannot be written to secondary storage unless they are within a file. Commonly files represent programs (both source and object forms) and data.

-Data files may be numeric, alphanumeric, or binary. Files may be free form, such as text files, or may be formatted rigidly. A file is a sequence of bits, bytes, lines or records whose meaning is defined by the file’s creator and user.

Many different types of information may be stored in a file:

-source programs, object programs, executable programs , numeric data, text ,payroll records, graphic images, sound recordings and so on. A file has a certain defined structure according to its type.

-A text file is a sequence of characters organized into lines ; a source file is a sequence of subroutines and functions, each of which is further organized as declarations followed by executable statements; an object file is a sequence of bytes organized into blocks ; an executable file is a series of code sections that the loader can bring into memory and execute .


To provide an efficient and convenient access to the disk, the operating system imposes a file system to allow the data to be stored, located and retrieved easily. A file system poses two quite different design problems.

-The first problem is defining how the file system should look to the user. This task involves the definition of a file and its attributes, operations allowed on a file, and the directory structure for organizing the files.

-Next, algorithms and data structure must be created to match the logical file system onto the physical secondary storage devices.

The file system itself is composed of many different levels. Each level in the design uses the...
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