SAD-File Structure

Some of the basic terms used to describe the file hierarchy are as follows

Byte: A byte is an arbitrary set of eight bits that represent a character .It is the smallest addressable unit in today’s computers.

Data item (element): One or more bytes are combined into a data item to describe an attribute of an object. Sometimes referred as a field.

Record: The data items related to an object are combined into a record. There are two types of records

•   Logical record maintains o logical relationship among all items in the record.
•    Physical record is the way in which records are stored in a storage medium.

File: A collection of related records makes up a file. The  size of  a file is limited by the size of memory or the storage medium. There are two characteristics denoting the way files are organized

•   Activity specifies the percentage of actual records processed in a single run.
•   Volatility addresses the properties of record changes.

Data base: The highest level in the hierarchy is the database. It is a set of interrelated files for real time processing.