CITS2002 Systems Programming  
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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 18, p1, 24th September 2019.