OS-File

A file is a named collection of data. It normally resides on a secondary storage device such as a disk or tape. It may be manipulated as a unit by operations such as

• open – prepare a file to be referenced.
• close – prevent further reference to a file until it is reopened.
• create – build a new file.
• destroy – remove a file.
• copy – create another version of the file with a new name.
• rename – change the name of a file.
• list – print or display the contents of a file.

Individual data items within the file may be manipulated by operations like

• read – input a data item to a process from a file.
• write – output a data item from a process to a file.
• update – modify an existing data item in a file.
• insert – add a new data item to a file.
• delete – remove a data item from a file.

Files may be characterized by

• volatility – this refers to the frequency with which additions and deletions are made to a file.
• activity – this refers to the percentage of a file’s records accessed during a given period of time.
• size – this refers to the amount of information stored in the file.