13.1 User defined data types

Question 1

Why are user-defined data types neccessary?

Answer 1

Because each user-defined data type exist as a complete entity, including the data definitions, default values, and value constraints, this entity insures uniformity and consistency. Reusability - As a hierarchy of common data structures are assembled, these can be re-used within many definitions, saving coding time and insuring uniformity.

Reusability - As a hierarchy of common data structures are assembled, these can be re-used within many definitions, saving coding time and insuring uniformity.

Flexibility - The ability to create real-world data representations of data allows the database object designer to model the real world as it exists.

Question 2

What are the non-composite data types?

Answer 2

Enumerated

Pointer

Question 3

What is a non-composite data type?

Answer 3

A non-composite data type is defined without reference to another data type

Question 4

What is a composite data type?

Answer 4

A composite data type is built from other data types.

Question 5

Enumerated data type

Answer 5

An enumerated data type is a non-composite data type defined from an ordered list of values. Variables can be declared by this data type, and assigned one of the values in the list

Question 6

Pointer data type

Answer 6

A pointer data type references memory locations. Thus, it has to relate to the type of data that it is pointing to.

Question 7

What are the composite data types?

Answer 7

Record
Object
Set

Question 8

Record data type

Answer 8

A record data type stores a collection of information regarding a common subject, similar to a record in a database. It is constructed from several fields, which each have their own data types; thus, the record data type is a composite data type.

Question 9

Set data type

Answer 9

A set data type is a composite data type that allows a programmer to apply set theory operations to data in a program.
These operations typically include:

Union
Difference
Intersection
Including an element
Excluding an element
Checking whether an element is in a set

Question 10

Object data type

Answer 10

An object data type is a composite data type used in object-oriented programming to define classes.

Essentially, objects are just records with functions that act on the data that they contain.