Question

Mark the following statements as true or false. a. The member variables of a class must be of the same type. b. The member functions of a class must be public. c. A class can have more than one constructor. d. \(A\) class can have more than one destructor. e. Both constructors and destructors can have parameters.

Short answer

The truth values are: a. False, b. False, c. True, d. False, e. False.

Step-by-step solution

Analyzing Statement a

Statement a: The member variables of a class must be of the same type. Classes can have member variables of different types. For instance, a class representing a "Car" might have string variables for "color" and "model", and integer variables for "year" and "mileage". Therefore, this statement is false.

Analyzing Statement b

Statement b: The member functions of a class must be public. Member functions in a class can have different access specifiers: public, protected, or private. These determine their accessibility outside the class. Not all member functions need to be public. Thus, the statement is false.

Analyzing Statement c

Statement c: A class can have more than one constructor. Classes can indeed have multiple constructors with different parameters (parameter overloading). This allows for creating objects in different initial states. Therefore, this statement is true.

Analyzing Statement d

Statement d: A class can have more than one destructor. In C++, a class can only have one destructor, which is called when an object is destroyed. Destructors do not support overloading. Therefore, this statement is false.

Analyzing Statement e

Statement e: Both constructors and destructors can have parameters. Constructors can have parameters which allow for initializing an object's members during creation. However, destructors cannot have parameters and are called without arguments. Hence, this statement is false.

Key concepts

Member Variables

In C++, member variables are the attributes or properties that belong to a class. They define the data that the class can hold. These variables can be of various data types such as integers, floats, or even other objects.

One important aspect of member variables is that they do not need to be of the same type. For instance, if you are creating a class for a "Student", you can have member variables like an integer for "studentID" and a string for "name". This flexibility allows you to model real-world entities more accurately in C++.

Another key factor is initialization, where constructors often play a big role to set the initial state of member variables when an object is created. It's also important to keep in mind how member variables are accessed, which we will discuss under access specifiers.

Constructors

Constructors in C++ are special member functions that are called when a new instance of a class is created. Their primary purpose is to initialize objects. Constructors can be overloaded, meaning a class can have multiple constructors with different numbers or types of parameters.

This allows the same class to be instantiated in a variety of states. For example, a "Circle" class could have a constructor that takes a single "radius" value, or another that takes "radius", "x-coordinate", and "y-coordinate" to place the circle on a specific position in a 2D space.

• Default Constructor: A constructor with no parameters.
• Parameterized Constructor: A constructor with parameters that allows passing initial values.

It's important to remember that constructors do not have a return type, not even void.

Destructors

Destructors are also special member functions in C++. They are invoked automatically when an object goes out of scope or is explicitly deleted. The purpose of a destructor is to release resources that the object may have acquired during its lifetime.

A crucial point about destructors is that unlike constructors, a class can only have one destructor, and it cannot have parameters. This means you cannot overload destructors like constructors. Destructors start with a tilde (~) followed by the class name and have no return type.

For example, if a class named "FileHandler" opens a file on creation, its destructor would be responsible for closing that file when the object is destroyed, ensuring no resource leaks occur.

Access Specifiers

Access specifiers in C++ define the accessibility of class members such as member variables and functions. The three main types of access specifiers are public, protected, and private.

Public members are accessible from anywhere in the program where the object is visible. These are typically functions that provide a way to interact with the object from outside the class.

• Private members can only be accessed by member functions of the same class, emphasizing encapsulation.
• Protected members are similar to private members, but they can also be accessed in derived classes.

Choosing the right access specifier is crucial for maintaining the integrity of an object's data and ensuring that it cannot be changed in an invalid way by an external source. This practice follows the principle of encapsulation, a key principle of object-oriented programming.