FIT2070 Lecture 11: FIT2070 - Lecture 11: File Management Notes
13 Jun 2018
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L11 - File Management
Files
● Data collections created by users
● Properties
○ Long-term existence
■ Files stored on disk or other secondary storage
■ Do not disappear when a user logs off
○ Sharable between processes
■ Files have names
■ Can have associated access permissions that permit controlled
sharing
○ Structure
■ Can be organised into hierarchical order
■ Or more complex structure to reflect the relationships among files
File Systems
● Means to store data organised as files
● A collection of functions that can be performed on files
○ Create
○ Delete
○ Open
○ Close
○ Read
○ Write
● Maintain a set of attributes associated with the file
Structure Terms
● Field
○ Basic element of data
○ Contains a single value
○ Fixed or variable length
● Database
○ Collection of related data
○ Relationships among elements of data are explicit
○ Designed for use by a number of different applications
○ Consists of one or more types of files
● Record
○ Collection of related fields that can be treated as a unit by some application
program
○ Fixed or variable length
● File
○ Collection of similar records
○ Treated as a single entity
○ Can be referenced by name
File Management System Objectives
● Meet the data management needs and requirement of the user
● System service that is served by the OS
● Ensure data in files are valid
● Optimise system performance
● Provide I/O support for a variety of storage device types
● Minimise potential for lost or destroyed data
File System Software Architecture
Device Drivers
● Communicates directly with peripheral devices
● Responsible for starting I/O operations on a device
● Processes the completion of an I/O request
Basic File Systems
● Primary interface with the environment outside the computer system
● Deals with block of data that are exchanged with disk or tape systems
● Concerned with the placement of blocks of the secondary storage device
● Part of the OS
Basic I/O Supervisor
● Responsible for all file I/O initiation and termination
● Selects the device on which the I/O is to be performed
● Concerned with scheduling disk and tape accesses to optimise performance
● I/O buffers are assigned and secondary memory is allocated at this level
Document Summary
Files stored on disk or other secondary storage. Do not disappear when a user logs off. Can have associated access permissions that permit controlled sharing. Or more complex structure to reflect the relationships among files. Means to store data organised as files. A collection of functions that can be performed on files. Maintain a set of attributes associated with the file. Relationships among elements of data are explicit. Designed for use by a number of different applications. Consists of one or more types of files. Collection of related fields that can be treated as a unit by some application program. Meet the data management needs and requirement of the user. System service that is served by the os. Provide i/o support for a variety of storage device types. Minimise potential for lost or destroyed data. Responsible for starting i/o operations on a device. Processes the completion of an i/o request. Primary interface with the environment outside the computer system.
