Organisation of File Systems
A clear and obvious requirement of an operating system is the provision of
a convenient, efficient, and robust filing system.
The file system is used not only to store users' programs and data, but
also to support and represent significant portions of the operating system
itself.
Stallings introduces the traditional file system concepts of:
- fields
- represent the smallest logical item of data "understood" by a
file-system: examples including a single integer or string. Fields may be
of a fixed length (recorded by the file-system as "part of" each file), or
be of variable length, where either the length is stored with the field or
a sentinel byte signifies the extent.
- records
- consist of one or more fields and are treated as a single unit by
application programs needing to read or write the record. Again, records
may be of fixed or variable length.
- files
- are familiar collections of identically represented records, and are
accessed by unique names. Deleting a file (by name) similarly affects its
component records. Access control restricts the forms of operations that
may be performed on files by various classes of users and programs.
- databases
- consist of one or more files whose contents are strongly
(logically) related. The on-disk representation of the data is considered
optimal with respect to its datatypes and its expected methods of access.
CITS2002 Systems Programming, Lecture 15, p1, 18th September 2023.
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