Question

Consider the following declarations: class xClass { public: void func(); void print() const ; xClass (); xClass (int, double); private: int u; double w; }; and assume that the following statement is in a user program: xClass x; a. How many members does class xClass have? b. How many private members does class xClass have? c. How many constructors does class xClass have? d. Write the definition of the member function func so that u is set to 10 and w is set to 15.3. e. Write the definition of the member function print that prints the contents of u and w. f. Write the definition of the default constructor of the class xClass so that the private member variables are initialized to 0. g. Write a C++ statement that prints the values of the member variables of the object x. h. Write a C++ statement that declares an object t of type xClass and initializes the member variables of t to 20 and 35.0, respectively.

Short answer

a. 6 members; b. 2 private members; c. 2 constructors; d. See step 4; e. See step 5; f. See step 6; g. `x.print();`; h. `xClass t(20, 35.0);`.

Step-by-step solution

Identify Class Members

The class `xClass` contains four public member functions: `func`, `print`, `xClass()`, and `xClass(int, double)`, and two private data members: `u` and `w`. Thus, there are six total members of the class.

Count Private Members

The class `xClass` has two private members specified in the `private` section: the integer `u` and the double `w`.

Count Constructors

The class `xClass` has two constructors defined: the default constructor `xClass()`, and a parameterized constructor `xClass(int, double)`.

Define Member Function func

To define the member function `func`, it should set the private member `u` to 10 and `w` to 15.3. The definition will look like this: ``` void xClass::func() { u = 10; w = 15.3; } ```

Define Member Function print

To define the member function `print`, it should output the values of `u` and `w`. As `print` is a `const` function, it cannot modify member variables. The definition will look like this: ``` void xClass::print() const { std::cout << "u: " << u << ", w: " << w << std::endl; } ```

Define Default Constructor

The default constructor should initialize member variables `u` and `w` to 0. The definition will look like this: ``` xClass::xClass() { u = 0; w = 0.0; } ```

Print Object x's Member Variables

To print the member variables of the object `x`, you would call the `print` function on `x`: ``` x.print(); ```

Declare and Initialize an Object

Declare an object `t` of type `xClass` and initialize it using the parameterized constructor with values 20 and 35.0: ``` xClass t(20, 35.0); ```

Key concepts

Member Functions

Member functions in C++ are functions defined inside a class and can operate on class data members. They are the actions that an object of the class can perform. In the given class `xClass`, the member functions include `func()`, `print()`, and two constructors.

• `func()`: This is used to assign specific values to the private member variables `u` and `w`. The functionality is defined in such a way that `u` is set to 10 and `w` is set to 15.3.
• `print()`: This function is designed to output the values of `u` and `w`. It's marked as `const`, indicating that it doesn't alter any member variables, which is crucial for providing readonly access to the class data.

By using these member functions, one can manipulate and access the private data of the class in a controlled manner.

Constructors in C++

Constructors in C++ are special member functions with the same name as the class. Their main role is to initialize objects of that class. In `xClass`, there are two types of constructors: a default constructor and a parameterized constructor.

• The default constructor `xClass()` is designed to initialize the private members to default values, specifically 0 in this context. It provides an automatic way to set the initial state of an object.
• Parameterized constructor `xClass(int, double)`: This allows for the creation of an object with specified initial values for the data members `u` and `w`. When an object is created using this constructor, the passed values replace the default initialization.

Using constructors ensures objects are correctly set up right from the moment they are instantiated.

Private and Public Members

In C++, data within a class is often segregated into private and public sections. This separation implements encapsulation, controlling access to the various members of the class.

• **Private Members**: These members can only be accessed and modified by the class's member functions. In `xClass`, `u` and `w` are private, meaning direct access from outside the class is restricted. Private access secures the data, ensuring it’s only modified in well-defined ways.
• **Public Members**: These are accessible from outside the class. In the `xClass`, the functions `func()`, `print()`, and the constructors are public, which means they can be called by other parts of the program. By keeping functions public, but data private, a class provides methods of interaction while protecting its internal state.

This methodology aligns with the fundamental OOP principle of data hiding.

C++ Object Initialization

Initializing an object means setting up an instance of a class with a valid state, typically through constructors. This process is vital to ensure that objects behave predictably upon creation.

• When an object like `x` of type `xClass` is declared without parameters, the default constructor is utilized, initializing `u` and `w` to 0.
• For creating an object like `t` with specific values (e.g., 20 for `u` and 35.0 for `w`), the parameterized constructor is used. This allows customization of an object's initial state directly during its creation.

Object initialization is crucial in managing the lifecycle and state of an object, ensuring that it's ready for use in its programmed environment. Proper initialization prevents unexpected behavior in your C++ program.