File Management

File Manager Functions

• keep track of where each file is stored

• implement a policy that’ll

  • determine where + how files are stored

  • efficiently use available storage space

  • provide efficient file access

• allocate each file when a user has been cleared for access to it, then record its use

• File deallocation

Types of Files

• Program files

• Data files

File Manager Interactions

• embedded in program

  • OPEN, CLOSE, READ, WRITE, MODIFY

• submitted interactively

  • CREATE, DELETE, RENAME, COPY

Volume Configuration

• each secondary storage is considered a volume

• each volume is given a name, and the File manager manages it(writes descriptive info)

• single directory per volume

Volume Configuration Disadvantages

• Long search time for individual file

• Directory space filled before disk storage space filled

• Users cannot create subdirectories

• Users cannot safeguard their files

• Each program needs unique name

  • Even those serving many users

    
    

MFD

• stored immediately after volume descriptor

• lists:

  • names & characteristics of every file in volume

  • any subdirectories

  • the remainder of the volume

File Descriptor

• Filename: ASCII code

• File type: organization and usage

  • System dependent

• File size: for convenience

• File location

  • First physical block identification

• Date and time of creation

• Owner

• Protection information: access restrictions

• Record size: fixed size, maximum size

  
  

File Naming Conventions

• Relative filename and extension(.png)

• Operating System Specifics

  • Windows

    • Drive label and directory name, relative name, and
      extension

  • Network w/ Open VMS Alpha

    • Node, volume or storage device, directory, subdirectory, relative name and extension, file version number

  • UNIX/Linux

    • Forward slash (root), first subdirectory, sub-
      subdirectory, file’s relative name

Absolute File Names(Complete filename)

includes all path info

Relative File Names

• Name without path information

• Appears in directory listings, folders

• Provides filename differentiation within directory

• Varies in length

  • One to many characters

  • Operating system specific