ENVS 1500 Lecture 30: ENVS 1500 Lecture 30 Notes
13 May 2018
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ENVS 1500 Lecture 30 Notes – Consistent View
Introduction
• The file management system provides a consistent view of files across different I/O
devices.
• This view even extends to files located elsewhere, on devices accessible from a network.
• To the user, file requests operate in the same way independent of the device, even
between devices of different characteristics.
• Thus, it is not necessary to know the physical differences between, say, disk and tape, to
move a file from one to the other.
• A program can request file services without knowing the file structure of the device
being addressed, indeed without even knowing what kind of device the file is stored on.
• The file management system provides and maintains
• Directory structures for each I/O device in the system and tools to access and move
around these structures
• The directory structure allows the retrieval and storage of files by name, keeps track of
the mappings, allocates and frees space, allows the mounting and unmounting of file
structures, and provides other functions required to maintain the structures of the file
system.
• Provisions are made to move easily from one structure to another.
• Tools that copy and move files from one I/O device to another and from one directory
to another, merge files, create and delete files and directories, and undertake other
basic file manipulations
• Information about each file in the system and tools to access that information
• Typically, information about a file might include its name, type of file, size, date and
time of creation, date and time of the most recent update, and protection and backup
characteristics.
• Security mechanisms to protect files and control and limit file access to authorized
users.
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