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File Management
COMP3231
Operating Systems
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References
• Textbook
– Tanenbaum, Chapter 6
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Files
• Named repository for data
– Potentially large amount of data
• Beyond that available via virtual memory
– (Except maybe 64-bit systems)
– File lifetime is independent of process lifetime
– Used to share data between processes
• Convenience
– Input to applications is by means of a file
– Output is saved in a file for long-term storage
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File Management
• File management system is considered
part of the operating system
– Manages a trusted, shared resource
– Bridges the gap between:
• low-level disk organisation (an array of blocks),
• and the user’s views (a stream or collection of
records)
• Also includes tools outside the kernel
– E.g. formatting, recovery, defrag, consistency,
and backup utilities.
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Objectives for a
File Management System
• Provide a convenient naming
system for files
• Provide uniform I/O support for
a variety of storage device
types
– Same file abstraction
• Provide a standardized set of
I/O interface routines
– Storage device drivers
interchangeable
• Guarantee that the data in the
file are valid
• Optimise performance
• Minimize or eliminate the
potential for lost or destroyed
data
• Provide I/O support and
access control for multiple
users
• Support system administration
(e.g., backups)
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File Names
• File system must provide a convenient naming
scheme
– Textual Names
– May have restrictions
• Only certain characters
– E.g . no ‘/’ characters
• Limited length
• Only certain format
– E.g DOS, 8 + 3
– Case (in)sensitive
– Names may obey conventions (.c files or C files)
• Interpreted by tools (UNIX)
• Interpreted by operating system (Windows)
