Dec1999 OP216 : Object Oriented Programming (Question 1)

(a)

(i)Explain the difference between a class and an object .[2 marks ]

(ii)State what a friend function is in C++.[2 marks ]

(iii)Give one example of when a friend function may be used.[1 mark ]

(iv)Explain the difference between multiple and single inheritance.
[2 marks ]

(v)Describe what is meant by a pure virtual function in C++.[2 marks ]

(vi)Declare a pure virtual function,called foobar ,which takes no parameters and has an int return type.[1 mark ]

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(b)

(i)Explain the difference between pass by value and pass by reference parameter passing,and describe how pass by reference is implemented in C++.[3 marks ]

(ii)Write a function,called avswap ,the signature of which is given below,which takes in two reference parameters x and y ,and returns the average of the two parameters.On exit,the values of x and y should be exchanged.int avswap(int* x, int* y); [5 marks ]

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(c)

(i)Define the purpose of a class constructor .[1 mark ]

(ii)Write a class,called StudentMarks ,which is to be used to store sets of student marks.Your class should contain the following member declarations:

•A default constructor;
•A default destructor;
•An array of integers,called Marks ,which is private .The array should be dynamically allocated.
•An integer,called NumMarks ,which can be used to store the length of the integer array. [4 marks ]

(iii)Add to your class the declaration of an overloaded constructor,which takes two parameters x which is an array of integers and y ,which is the length of the array.[1 mark ]

(iv)Add to your class an inline accessor function,called MarkAt ,which takes in a single parameter x ,and returns the value stored in the array at that index. [2 marks ]

(v)Add to your class a function,called ReadPass ,the signature of which is given below,which will return the index of the first element of the array to have a mark greater than 30,or -1 if there is none.
int ReadPass(); [4 marks ]

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