Question

What will the following code display? enum \(\\{\text { POODLE , BOXER, TERRIER }\\}\) cout \(<<\) POODLE \(<<\quad " \quad "<<\) BOXER \(<<\quad\) " \(\quad "<<\) TERRIER \(<<\) endl

Short answer

Answer: The output of the given C++ code is "0 1 2".

Step-by-step solution

Understand the enum declaration

An enum declaration defines a new type of variable with a set of named integer constants. In this case, the enum is declared with three elements: POODLE, BOXER, and TERRIER, representing different types of dogs.

Enum values assignment

When an enum is declared, the elements are assigned integer values starting with 0, incremented by 1 for each successive element, unless a specific value is assigned to any enum element. In this case, no values are assigned to the elements, so the default assignments will be POODLE = 0, BOXER = 1, and TERRIER = 2.

Understand the cout statement

The cout statement is used to display values on the console. In this case, each enum element's value is displayed, followed by a space represented by the quotations containing spaces.

Determine the final output

Based on the enum values and the cout statement, the output will be the integer values assigned to POODLE, BOXER, and TERRIER separated by spaces. Therefore, the final output will be "0 1 2".

Key concepts

Integer Constants in Enums

Enums are a way to define a group of related constants in C++. These constants are integer values assigned to named symbols within the enum. By default, the first element is given the value 0, and each subsequent element has a value that is increased by 1.

For example, in an `enum` containing `POODLE`, `BOXER`, `TERRIER`, C++ assigns these values:

• `POODLE = 0`
• `BOXER = 1`
• `TERRIER = 2`

You could customize these values by assigning specific numbers to them. However, if you don't, these default values help manage and represent the constants easily by their integer values behind the scenes.

Using cout in C++

The `cout` statement is crucial for displaying information to the screen in C++ programs. It stands for 'console output' and is used alongside the insertion operator `<<` to stream data for output.

In our example, the expression `cout << POODLE << " " << BOXER << " " << TERRIER << endl;`

• Begins by fetching the integer value of `POODLE`, which is 0, and outputs it.
• Inserts a space (" ") to separate it from the next output.
• Fetches and outputs `BOXER`'s integer value of 1.
• Inserts another space.
• Finally, fetches and outputs `TERRIER`'s value of 2.

Using `cout` allows dynamic display of variable results, helping developers understand what a program does by viewing its output. This example neatly shows the integer representations of each named constant of the enum.

Enum Declaration in C++

Enum declarations are a way to define user-friendly names for values that are also simple to manage as integer constants. They are declared using the keyword `enum` followed by a set of identifiers. These identifiers act as named constants.

Here’s how the enum in the example is declared:
```cpp enum { POODLE, BOXER, TERRIER }; ``` This syntax initializes a new enum with members `POODLE`, `BOXER`, and `TERRIER`. Since no explicit values are assigned, they are automatically given sequential integer values starting from 0.

Enums are particularly beneficial when you want to use human-readable names for constant values. They reduce errors related to using magic numbers by allowing the use of symbolic names, which make the code more readable and maintainable.