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 (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