Different File Type from Storage
point of view
/>
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.
/>
There are main three type of files from
storage point of view.
Sequential
files
Direct or random files
/>
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.
/>
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.
/>
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.
/>