C++ Enumeration (enum)

In C++, an enumeration (enum) is a special data type that represents a set of constant values. It allows for better readability when working with predefined categories or states.

Defining an Enum

To create an enum. use the enum keyword followed by its name and a list of constants inside curly braces {}.

Example: Declaring an Enum

enum EngineState {  
    OFF,  
    IDLE,  
    RUNNING  
};

This enum groups three constant values:

• OFF (default value 0)
• IDLE (default value 1)
• RUNNING (default value 2)

Using an Enum

To work with an enum, declare a variable of its type.

Example: Assigning and Printing Enum Values

#include <iostream>
using namespace std;

int main() {
    // Create an enum variable and assign a value
    enum EngineState engineStatus = IDLE;

    cout << engineStatus;  // Outputs: 1

    return 0;
}

Since IDLE is the second item, its default value is 1.

Customizing Enum Values

By default, enums start at 0 and increment by 1, but you can assign custom values.

Example: Custom Enum Values

enum EngineState {  
    OFF = 10,  
    IDLE = 20,  
    RUNNING = 30  
};

int main() {
    EngineState engineStatus = IDLE;
    cout << engineStatus;  // Outputs: 20

    return 0;
}

Custom values help improve clarity in programs.

Automatic Value Increment

If you set a value for one item, the next ones automatically increase.

Example

enum EngineState {  
    OFF = 100,  
    IDLE,  // 101  
    RUNNING  // 102  
};

Using Enum in a switch Statement

Enums are often used in switch cases for structured decision-making.

Example: Evaluating Engine Status

#include <iostream>
using namespace std;

enum EngineState {  
    OFF = 0,  
    IDLE,  
    RUNNING  
};

int main() {
    EngineState engineStatus = RUNNING;

    switch (engineStatus) {
        case OFF:
            cout << "Engine is OFF.";
            break;
        case IDLE:
            cout << "Engine is IDLING.";
            break;
        case RUNNING:
            cout << "Engine is RUNNING.";
            break;
    }

    return 0;
}