Different File Type from Storage point of view

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Different File Type from Storage

point of view






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File organization is

a technique for storing and arranging data on

secondary storage devices so that it can be

retrieved easily when needed. It includes the

physical order and layout of records on

secondary storage devices. The techniques used

to write and retrieve data to and from the

storage devices called it access methods.

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There are main three type of files from

storage point of view.

Sequential

files

Direct or random files

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Indexed sequential file


/>Sequential Files

In sequential

data files, records are stored on the storage

media in a sequence. No locations are specified

for individual records. The records are stored

in an order, one after the other. Similarly,

records are also retrieved in sequential order.

It means that records are accessed one after the

other in the same sequence in which they are

stored on the storages devices. For example, to

access a particular record from a data file, all

records are searched one by one until the

specified record in found. Therefore, accessing

records in sequential files is very slow.

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Direct or Random files


/>Direct files are also referred to as random

files. In these files, records are not stored in

a sequence. Each record is stored by specifying

a particular address or location within a file.

The address is calculated against the value of

the key field of the record. Sometimes, the same

address is calculated, which creates a problem

to store record. This problem is known as

synonym. Data accessing from direct files is

very fast. A record is accessed directly by

specifying its address.

Indexed

Sequential Files

These files can be

processed sequentially as well as randomly. In

these files, the location of individual record

is also stored along with data of record. For

this purpose, an index is created to keep the

track of locations of individual records.

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Index refers to the location on the

storage media where record is stored. You can

say that an index is just like a table that is

used to find out the location of a particular

record. The key fields of the records are stored

separately into the index along with the address

of each record. Usually, an index is created in

a new file called index file. The index file is

updated whenever a new record is added or an

existing record is deleted. Indexed file

organization is more effective and fast in

accessing data from data file than sequential

file organization. These files occupy more space

on the storage media but accessing speed of

records is same as random access files.


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