MECH 2301 Lecture Notes - Lecture 14: Management System
20 May 2018
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MECH 2301 Lecture 14 Notes
Introduction
The role of the file management system
• Note that it is the logical view that gives the data in a file meaning.
• Physically, the file is simply a collection of bits stored in blocks.
• It is the file management system that establishes the connection between the logical
and physical representations of the file.
• Tape organization is somewhat different.
• Most tape systems use a variable size block
• So it is possible to store a file exactly, with no internal fragmentation.
• Furthermore, some file management systems separate logical records into different
blocks, making it possible to record individual records on tape.
• The file management system is commonly called the file manager.
• We will priarily use the ter file aager, so please reeer e are talkig aout
a software program, not a person!
• The file aager ats as a trasparet iterfae etee the users logial ie of the
file syste ad the oputers physial reality of disk sectors, tracks, and clusters, tape
blocks, and other I/O vagaries.
• It provides a consistent set of commands and a consistent view of files to the user
regardless of the file type, file characteristics, choice of physical device, or physical
storage requirements.
• It translates those commands to a form appropriate for the device and carries out the
required operation.
• To do so, it maintains directory structures for each device.
• These, too, are preseted i logial for to the user ad to the users programs.
• User file commands and program file requests are interpreted by the command shell
• Then passed in logical form as requests to the file manager.
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