What is a enumerated data type?

Answer 1

An enumeration is a group of (closely) related constants of integral type (int, char, short, long or long long).

Members of an enumeration are automatically initialised with values in the order they are declared, starting with the value 0 for the first member and incrementing by 1 for each additional member:

enum traffic_light {green, amber, red}; // e.g., green=0, amber=1, red=2

If the start value 0 is undesirable, we can assign a different start value:

enum traffic_light {green=1, amber, red}; // e.g., green=1, amber=2, red=3

A new start value can be placed anywhere in an enum:

enum traffic_light {green, amber=4, red}; // e.g., green=0, amber=4, red=5

Two or more members can share the same value:

enum traffic_light {green, amber, orange=1, red}; // e.g., green=0, amber=1, orange=1, red=2

The value of a previously declared member can be used to initialise another member:

enum traffic_light {green, amber=green+1, red=green+2}; // e.g., green=0, amber=1, red=2

The names of an enumeration are within the scope of the declaration. This is often undesirable as two enumerations in the same scope cannot share the same member names:

enum traffic_light {green, amber, red};

enum rainbow {red, orange, yellow, green, blue, indigo, violet}; // error!

To avoid this, we can use an enum class. The enumeration then becomes a namespace:

enum class traffic_light {green, amber, red};

enum class rainbow {red, orange, yellow, green, blue, indigo, violet}; // ok

To refer to a member of an enum class, we use namespace resolution:

traffic_light x = red; // error! no red in scope

rainbow y = rainbow::green; // ok

Answer 2

An enumerated data type is a manufactured data type. The orginal implementation of the boolean data type was an enumerated type.

enum boolean {true, false};

this creates a type : boolean and two constants of type boolean: true and false.

true has an integer value: 0

false as an integer value: 1

The way boolean is now implemented in C and C++ and C# maintains the convention that 0 is true.

A common use of enumerated types is in game programming. You can enumerate the cardinal directions, for example, north, east, south, west, so that you can turn right by performing:

enum compass {north, east, south, west};

compass direction = west;

direction = (direction + 1) % 4

// at this point, direction would be equal to north, or 0

Answer 3

Enumerated data type is a set of values which are going to be used in the program as constant variables. We can assign any integral value to each member in the set.