File System - concept

File System - concept

The basic concepts of file system

File system is a computer organization, an important means of information access and preservation.

Historical process data storage media

• Card paper tape
• Direct access to a large capacity disk storage and tape storage sequentially accessed
  • Magnetic tape, drum
  • Hard disk, floppy disk
  • Disk arrays, CD-ROM,
  • U disk, memory card
• File system has
  1. The respective programs and data as files and store them on disk or tape and other large-capacity storage medium
  2 thereby leading to transparent access to program and data. Not need to know the access related part of the physical structure of the media file storage and lookup method, only given a file name representative of a certain program or data file to a system for operating the automatically given file name corresponding to the file.

File system to complete the work

1. In order to properly file storage, disk space and other auxiliary memory (also known as file space) for unified management. Assigned to the free zone when a user creates a new file, the user delete or modify a file, recovery and adjust the storage area.
2. In order to achieve access by name, requires a user-visible document logical structure. User information access and processing according to the document logical structure given way, the logical file structure independent of the physical storage devices.
3. In order to facilitate storage and processing of information, a file stored on the storage device in a certain order. This store is called the physical structure of the document.
4. Complete the look of the store on a storage device's file information.
5. Complete share files and provide protection.

The concept of file and file system

file

A program or file is a collection of data.

File formats

Fu character stream file name

A flat-file or streaming file
2. The file is a stream of characters unstructured manner, source code, object code, etc. is the same in form, and hence also for the source program, the object code files and the like.

File composed by an associated record

1. The basic unit is the recording information
2. mainly used for information management database systems

file name

User file name given by the user, but there are certain rules

File system

Operating system software and data files associated with the management called a file system.

• Create documents,
• Revoke
• Read and write
• Modify and copy files
• Complete access files by name and access control

Features:
1. The user-friendly interface, the user only operate on the document, and regardless of the physical location of the file structure and storage.
2. Press the name to access files
3. Support multiple users share files or processes.
4. Support disk, tape and CD-ROM as the mass memory storage medium, and therefore a large amount of information stored.

Document classification

According to the nature and use classification:

• File system
  only allows users to execute system calls the class file, you can not read, write and modify. These documents mainly by the operating system kernel and various system applications and data.
• Libraries
  allow users to read, execute such documents, but not edit it. The main library files from a variety of standard subroutine libraries. Such as the C language subroutine library, FORTRAN subroutine libraries.
• User files
  stored in the user delegate file system. File owner or file owner authorized users have access to such documents. User files, including source code, object program, user databases.

In the form of file organization:

• Trivial File
  ordinary file includes both system files, including user files and library functions files, utility files.
  Common file format for the organization mainly refers to the most common file system format as specified, generally refers to unstructured file stream of characters composed.

• Directory file
  directory file is a special file consisting of directory information file. That is not the contents of the file or application data of various programs, but to retrieve directory information ordinary file.

• Special files
  in UNIX systems, all input and output devices are considered special file. (Stdin, stdout, stderr)
  specific set of files with the same file in the ordinary use form, such as directory lookup, the access operation.

According to the flow of information in the file classification:

• Input File
• Output file
• Input / output documents.

By file-level protection classification:

• Read-only file
• Reading and Writing Files
• executable file
• Does not protect files.

The purpose file classification:
the main system is easy to be different for different file management, and to improve processing speed and play a role in the protection and sharing.