The structures of files vary from operating system to operating system. In this unit, we will discuss the fundamentals of file structures with the generic file organisations.

A file may be described as a collection of records. Though, a text file doesn't conform to this definition at the first glance, it is also a set of records and records are words in the file.

Let a file consisting of information regarding students. We may name such a file as Student file. The typical records of such file are illustrated in Figure

                             Figure: Typical records of a Student file

A file should always be stored in such a way that the fundamental operations on it can be performed easily. In other terms, queries must be able to be executed without much hassle. We target, in this unit, on the ways of storing the files on external storage devices. Selection of a specific way of storing the file on the device based on factors such as retrieval records, the way the queries can be put onto the file, the total number of keys in each of record etc.

After learning this unit, you must be able to

• Study the terminology of file structures;
• learn the underlying concepts of Sequential files, and
• know about the Indexed sequential file organization.