Data Type in Data Structure

               Before discussing data type in data structure, i am going to describe data, basis of categorization of these data, and advanced categories of data. 

DATA :- Data can be defined as a value or set of values. These values may represent some observations from an experiment, some figures collected during some surveys, marks obtained by a student in an examination, etc.

DATA ITEM :- A data item refers to a single unit of values. For example, roll no., name, date of birth, age, address and marks in each subject are data items. 

                 Data items that can be divided into sub items are called group items whereas those item which cannot be divided into sub - items are called elementary items. For example, an address is a group item as it is usually divided into sub - items such as house no., street no., locality, city, pin code, etc. On the other hand roll no., marks, city, pin code are normally treated as elementary items.

ENTITY :- An entity is something that has certain attributes or properties which may be assigned values. The values assigned may be either numeric or non - numeric. 

                    For example : A student is an entity. The possible attributes for a student can be roll no., name, date of birth and class. Each attribute of an entity has a defined set of values called Domain.

ENTITY SET :- An entity set is a collection of similar entities.
                     For example : A student of a class, employees of an organization, products manufactured by a manufacturing unit etc. forms an entity set.

RECORD :- A record is a collection of related data items.
                     For example :