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Lists names & characteristics of every file contained in volume.
File names refer to program files, data files, and/or system files.
Subdirectories, if supported.
Remainder of volume is used for file storage.
Early OS supported only a single directory per volume.
Created by File Manager.
Contains names of files, usually organized in alphabetical, spatial, or chronological order.
Simple to implement and maintain.
Some major disadvantages
Volume Descriptor Creation Date Date when volume was created Pointer to Directory Area Indicates first sector where directory is stored Pointer to File Area Indicates first sector where file is stored File System Code Used to detect volumes with incorrect formats Volume News User-allocated name
Some Major Disadvantages of Single Directory Per Volume
Takes long time to search for an individual file, especially if MFD was organized in an arbitrary order.
If user has many small files stored in volume, directory space fills before disk storage space fills. User told “disk full” when only directory full.
Users can’t create subdirectories to group related files.
Multiple users can’t safeguard files from other users browsing file lists ‘cause entire directory listed on request.
Each program in entire directory needs unique name.
E.g., Only 1 person using directory can name program PROG1.
Semi-sophisticated File Managers create MFD for each volume with entries for files & subdirectories.
Subdirectory created when user opens account to access computer.
MFD entry flagged to indicate subdirectory with unique properties.
Improvement from single directory scheme.
Still can’t group files in a logical order to improve accessibility & efficiency of system.
Subdirectories Can Be Implemented As an Upside-down Tree
Today’s File Managers allow users to create subdirectories so related files are grouped together.
Extension of previous two-level directory structure.
Tree structures allow system to efficiently search individual directories due to fewer entries in each.
Path to requested file may lead through several directories.
When user wants to access specific file, file name is sent to File Manager. File Manager searches MFD for user's directory. Then searches user's directory & any subdirectories for requested file & location.