ENUMERATED DATATYPES
USER DEFINED DATA TYPES
Data Type Defined By Programmer
Allows Use Of More Complex Data
Typically Defined Globally So Variables Of The
Type Can Be Declared Wherever Needed
Types Include:
enumerated
arrays
structures
array of structures
linked list
ENUMERATED DATA TYPE
User Defined Type
Used To Increase Readability Of Programs
Assigns Meaningful Name To Value
Programmer Defines Names Of Values
Internal Data Type That Cannot Be Read Or
Written
ENUMERATED DATA TYPE
Requires List Of Values (Enumerated Constants)
List Is Identified With A New Data Type
Values Are Not char, string Or Number
No ‘ ‘ or “ “ Around Constants
Constants Must Be Valid Identifier Names
Constants Cannot Be Used In Another
Enumerated Data Type In Same Program
Proper Syntax:
enum colors {BLACK, RED, GREEN, BLUE, BROWN};
ENUMERATED DATA TYPE
Declaring Data Type Does Not Allocate Memory
Variables Of Type Needs To Be Declared
colors shirtColor, pantColor
This Creates Two Variables That Can Store
Enumerated Constant
shirtColor = RED;
pantColor = BLUE;
ENUMERATED DATA TYPE
The Enumerated Constants Are An Ordered List
Of Values (ordinal type)
The First Constant Has The Ordinal Value Zero
Each Successive Constant Is One Greater
Internally The Data Type Stored When Using The
Enumerated Constant Is Integer
cout << pantColor << ‘ ‘ << shirtColor << endl;
displays: 3 1
ENUMERATED DATA TYPE
Constants Are Ordinal So Relational Operators
Can Be Used
if (shirtColor > pantColor)
cout << “You May Want To Change Your Shirt” << endl;
Arithmetic Operators Cannot Be Used Directly
shirtColor = pantColor + 1; // THIS IS ILLEGAL
 However Use Of Static Cast Allows Addition / Subtraction
shirtColor = static_cast<colors>(pantColor + 1) // IS LEGAL
ENUMERATED DATA TYPE
WARNING, WARNING, WARNING….
There Is No Predecessor Before The First
Constant And No Successor After The Last
Constant
Trying To Subtract One From The First Or Add
One To The Last Causes An Undefined Value
ENUMERATED DATA TYPE
Two Major Drawbacks:
Cannot Be Input Directly From Keyboard
Cannot Be Output Directly To The Screen (except for
ordinal value)
Solving Problem Requires:
Creating An Input Function That Accepts Allowed
Input And Converts To Enumerated Value
Creating An Output Function That Converts
Enumerated Value To A Value That Can Be Displayed
ENUMERATED DATA TYPE
In The End:
Enumerated Data Types Provide For More Readable
Code
But Often Require Extra Coding To Make Them
Useable