FILE ORGNIZATION
File organization refers to the logical relationships among various records that constitute the
file, particularly with respect to the means of identification and access to any specific record.
File organization is used to describe the way in which the records are stored in terms of
blocks, and the blocks are placed on the storage medium. In short, it refers to the way in
which data records are stored or arranged.
Types of file organization
1. Serial (heap) files organization: records are placed in the order in which they are inserted.
A new record is inserted in the last page of the file; if there is insufficient space in the last
page, a new page is added to the file. This makes insertion very efficient but since heap file
has no particular ordering with respect to field values, a linear search must be performed to
access record as thus making it slower as compared to sorted files.
2. Sequential file organization: records are stored in some sort of order (ascending,
descending or alphabetical) based on the unique key field or search key. This method is fast
& efficient for huge amount of data. Sorted file is inefficient as it takes time & space for
sorting records. A sequential file could be stored on a sequential storage device such as
magnetic tape and magnetic disks. To access these records, the computer must read the file
in sequence from the beginning. The first record is read and processed first, then the second
record in the file sequence, and so on.
3. Index Sequential Access Method (ISAM): Records are organized in sequence and an index table is used
to speed up access to the records without requiring a search of an entire file. The records of the files can
be stored in a random sequence but the index table is in a sorted sequence on the key value. This type
of file organization is best suited for situations where both batch and online processing are to be
supported.
4. Direct or Random file organization: In this file organization, records are organized in such a way that it
is possible for the computer to directly locate the key of the desired record without having to search
through a sequence of the record. Direct file organization allows direct access to individual records
stored in any part of the file. These types of files are used in direct access storage device (DASD)
like floppy disk, hard disk and optical disk.
File access
When a file is used, information is read and accessed into computer memory and there are
several ways to access this information of the file. The file accessing methods are:
1. Direct access: the information/data stored on a device can be accessed randomly and
immediately irrespective to the order it was stored. The data with this access method is
quicker than sequential access. This is also known as random access method. For example
hard disk, flash drive etc.
2. Sequential access: the information/data stored on a device is accessed in the exact order
in which it was stored i.e. one record after another e.g. magnetic tape.
3. Random access: Random access file organization allows users to access files in any order,
rather than sequentially. This makes it faster and more efficient to find specific data.
File Classification (According to Use)
DEFINITION OF A MASTER FILE: It is defined as a file which shows the current state of some
aspects of an organization’s activities. It is therefore a semi-permanent reference
information usually on disk or tape in a stored form which undergoes updates, maintenance,
amendments, deletion and insertion and can also generate other master files.
DEFINITION OF A TRANSACTION FILE.
The teacher defines a transaction file as a file which contains changes made to the master
files. It is also called transient data and so has no static qualities because it is not retained
for a long period of time.
DEFINITION OF A REFERENCE FILE.
It is a file with a reasonable degree of permanency. Data used for reference purposes
include price list, salary table, names, address, tax table, table of rates etc.
OTHER TYPES OF FILES:
Program file: contains a program or program module.
Data file: contains relevant data only i.e user’s file
Document /text file: used in conjunction with word processing or desktop publishing
applications.
Work file: it is a file created under works application.
Scratch file:it is a file that is no longer needed and could be overwritten.
System files: these are files that the computer needs to boot, operate etc.
Movement file: a file utilized to convey updated information from one section or
department to another in an organization.
THE CRITERIA FOR CLASSIFYING FILES.
Nature of contents
Organization method
Storage medium
