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(a) Briefly explain the difference between
multiple and single inheritance. [2 marks]
(a) • Multiple inheritance is when a
class inherits from two or more base class trees; (1 mark)
• Single inheritance is when a class only inherits from one base
class tree; (1 mark) [2 marks]
(b) State the scope of each of the public,
protected and private areas of a class in a derived class where the
derived class is declared to inherit protected from the base class.
[3 marks]
(b) • The public members become protected;
(1 mark)
• Protected members stay protected; (1 mark)
• Private members stay private; (1 mark)
[3 marks]
(c) The Rover Car company require a
new system to aid them in the design of new products. One of the products
they wish to design is a Tractor. A Tractor is both a Vehicle, and
a Tool. Consider the following definitions of the classes Vehicle
and Tool:
class Vehicle {
int NumberPassengers, EngineCapacity;
public:
Vehicle(int Passengers, int Capacity);
int GetPassengers();
}
class Tool {
char *Purpose, *PowerSource;
public:
Tool(char* p, char* s);
char* GetPurpose();
}
(i) Using inheritance, define the class Tractor such that it inherits
all the properties of both the Vehicle and the Tool class. Your class
should include the variable RoofType, which is a boolean variable
of type boolean, set to true if the Tractor
has a roof, and false otherwise. In addition to this, your class should
include a
constructor function, which takes all the parameters necessary to
initialise all the
member variables. [5 marks]
(i) A sample definition of Tractor follows:
class Tractor : public Vehicle, public Tool {
public:
boolean
RoofType;
Tractor(int
NumPass, int EngCap, char* Pur, char* Power, boolean Roof);
}
And the following marking scheme should be used:
• Declaring the class to inherit from Vehicle; (1 mark)
• Declaring the class to inherit from Tool; (1 mark)
• Including parameters in the constructor to initialise the members
inherited from Vehicle; (1 mark)
• Including parameters in the constructor to initialise the members
inherited from Tool; (1 mark)
• Including parameters in the constructor to initialise the native
members; (1 mark) [5 marks]
(ii) Define a class, called Component, which contains the attributes
ComponentName, which is a string, and ComponentPartNumber, which is
an integer. You should ensure that these attributes are accessible
to all other classes. [3 marks]
(ii) a sample definition of Component follows:
class Component {
pubic:
string
ComponentName;
int
ComponentPatrNumber;
}
And the following marking scheme should be used:
• Including the ComponentName of type string; (1 mark)
• Including the ComponentPartNumber of type int; (1 mark)
• Specifying that these are public; (1 mark)
[3 marks]
(iii) When a Tractor is built, it is not known how many components
will be required until it is finished. Add to your Tractor class an
array of type Component, the length of which is decided at allocation
time, such that this array is not accessible outside of any further
derived classes. [2 marks]
(iii) The following definition should be
added:
private:
Component a[];
And the following marking scheme should be used:
• Declaring the array; (1 mark)
• Stating it to be private; (1 mark)
[2 marks]
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