JSS THREE WEEK FOUR LESSON NOTE (ICT_223)

 

Jss3

TOPIC:  INFORMATION STORAGE AND RETRIEVAL II

Introduction

File organization could be defined as the method in which data or record is held on a file with the view of how they are accessed and retrieved.

Types of file organization methods

1.     Serial

2.     Sequential

3.     Index

4.     Direct access

Serial method: serial file organization can also be called unordered file organization. A file is said to have and unordered organization if the records held or stored in any particular order or sequence on the file. Records are stored as they arrive on first come first serve principle.

Sequential method: this involves arranging of records in a particular sequence according to their field e.g. in alphabetical or numerical order. For example, student’s registration is done in this manner and the intake of new students might mean the whole file would be written all over again.

Indexed method: this is the most commonly used file organization method. It uses an index based on the key field of the record. A  key field could be said to be a field in a record that uniquely defines a record in a file so that it can be quickly and easily accessed.

Direct method: direct method of file organization is the process of storing or retrieving data items without the necessity of reading any other stored data first. Records are placed randomly through out the file.

Types of storage

Storage could be categorized into two. This is based on how far they could hold data, they are:

       I.            Temporary storage

    II.            Permanent storage

Temporary storage: these are storage devices that store data and information for a short period of time. They are basically referred to as primary storage devices, internal memory or internal store. Temporary storage resides inside the CPU (central processing unit).

Permanent storage: these are storage devices that store data and information for a long period of time. They are also referred to as external storage, secondary storage or auxiliary storage. This storage   could hold data for a long period of time. Examples are CD, DVD hard disk drive, flash memory etc.




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