Enumeration is basically a way to represent a possible list of number values for a variable in friendly names or symbol forms. For e.g. if  you have to represent rainbow colours with 0 to 6 you can always write them more meaningfully as

enum rainbow { RED, ORANGE, YELLOW, GREEN, BLUE, INDIGO, VIOLET };

This will essentially give values from 0 to 6 to given colours in that order. so if following code is written –

enum rainbow { RED, ORANGE, YELLOW, GREEN, BLUE, INDIGO, VIOLET };
rainbow colour;
colour = YELLOW;
cout<<colour;

Then output would be 2 as YELLOW is the third variable and its value would be integer 2 automatically.

Observation while using enumerated data types:

Please make following observations in the above declaration and usage in code.

• The declaration begins with prefix enum with a user defined data type name which in this case is rainbow.
• The declaration contains friendly value names separated by comma in a structure or class like declaration with curly braces and following semicolon.
• When used it follows a simple syntax of datatype name followed by a variable name which in this case is rainbow colour;
• The assigned variable can now be assigned only a value from within the given value list range only. If any thing else is assigned to variable name then compiler error will return. For e,g.
  colour = YELLOW; is correct
  colour=MAROON; is not correct as it is not there in the symbol list defined.
  colour=2; will also not be correct as it may be internally assigned value but not present as a symbol in the given symbol list.
• Internally the symbol names in the list gets converted to values and when printed they print the value only.
• Enumeration may allow user given fixed values like –
  enum rainbow { RED=1, ORANGE=2, YELLOW=3, GREEN=4, BLUE=5, INDIGO=6, VIOLET=7 };

Advantages of Enumeration:

• Allows to check for fixed set of values only for any variable.
• Allows to provide friendly names to list of values.
• The default values for value list is generated automatically from 0 to further as per number of items in the list. (This is converse to #define where providing values is a must)
• Is a good technique to assign multiple value combination as OR or AND form to the same variable.
• Additional value settings can be provided to a variable easily.
  Watch Few Examples Here

Some Examples of Enumerated Data Types

• enum season{spring, summer,autumn,winter};
• enum gender{male,female,other};
• enum weekdays{monday,tuesday,wednesday,thursday,friday,sunday};
• enum cards{club,diamond,heart,spade};
• enum artist_primary_colours{RED, YELLLOW, BLUE};
• enum direction{east,west,north,south};
• enum error{Memory_Err,File_err,Hardware_Err,Communication_Err};
• enum session{morning,evening};
• enum boolean{false,true};
• enum attribs{bold,underline,italic};
• enum G7{Canada,France,Germany,Italy,Japan,UK,USA,EU};