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Department of Business Studies
BACHELOR OF BUSINESS & INFORMATION TECHNOLOGY
BIT 3102: object oriented programming II
Marking scheme
DATE: 18 th^ August 2012^ TIME: 08.00 am
INSTRUCTIONS:
• Answer Question ONE in Section A and Any other
THREE from Section B.
• Write your registration number on all sheets of
the answer book used.
• Use a new page for every question attempted and
indicate the question number on the space
provided on each page of the answer sheet.
• Fasten together all loose answer sheets used.
• Switch off all Mobile Phones and PDAs.
SECTION A: ANSWER ALL QUESTIONS {30 MARKS}.
QUESTION 1
a) Describe three types of classes required to work with data (disk): [3 Marks]
- ifstream for input - read from files
- fstream for both input and output - both read and write from/to files,
- And ofstream for output - write on files.
b) List and Explain the access Specifiers used in OOP [6Marks]
Public: data members and member functions are accessible outside the class. Protected: data members and member functions are only available to derived classes. Private: data members and member functions can’t be accessed outside the class.
c) What is public accessor method and why is it necessary? [4 Marks]
This is a class member function that other parts of the program call to either read or set the value of a private member variable. The general rule to ensure security and accessibility of the data is to keep class data private and create a public function called public accessor method.
d) Differentiate between the following.
i. Function overloading. [2 Marks]
Compile time polymorphism. The function is overloaded
ii. Operator overloading [2 Marks]
Compile time polymorphism. The function is overloaded. Requires creation of a function called operator function
e) Using a syntax code explain the following terms as used in C++ Programming.
i. Destructor [4 Marks] This is a special function in a class which has the same name as its class, has no return type and returns no value. Used to free computer when the data members of the class are destroyed/. Class rectangle { Int length;
SECTION B: ANSWER ANY THREE QUESTIONS {20MARKS EACH}.
QUESTION 2
a) Explain the term Abstract class [2 Marks]
This is a class designed to be specifically used as a base class. It contains at least one pure virtual function.
b) Using a simple program briefly explain the concept for multiple inheritance in C++
[4 Marks]
Process of creating new class from more than one existing classes.
class A //Base class
{}
class B //Base class
{}
class C : public A , public B // derived class
{}
c) (^) When is a virtual function made “pure”? And what is purpose of a having a pure function? [8 Marks]
- Pure virtual function is a function declared in a base class that has no definition relative to the base class
- When virtual function is declared in base class and redefined in derived classes.
- The function in the base class is seldom used for performing any task.
- When a virtual function equated to zero is called a pure virtual function
- Its function is described in the base class that has no definition relative to the base class.
- It only serves as a place holder a “do-nothing” function declare as virtual void display ( )=0;
- In such case the compiler requires each derived class to either define the function or redeclare it as a pure virtual function
d) Write a program that saves/writes students names to a disk file. [6 Marks]
// #include
#include
using namespace std;
int main ()
ofstream myfile; //object of type ofstream created
myfile.open ("example.txt");
myfile << "Names for Students.\n 1. Silas\n 2. Nkirote\n 3. Faith \n 4. Caleb\n 5. Patience\n";
myfile.close();
.1 return 0;
account::getdata(); cout <<"Enter Interest\n"; cin >>interest; cout<<"Enter Withdrawal amount\n"; cin>>withdrawal; } void putdata (void) { account::putdata(); cout<<"Interest\n :"<<interest; cout<<"Withdraw amount\n: "<<withdrawal; } }; int main () { saving s1; cout << "Enter data for savings account customer 1:"; s1.getdata(); cout<<"Display data on savings account customer 1:"; s1.putdata(); return 0; }
b) Discuss the three major components of the Standard Template Library [5 Marks]
- A container: is an object that actually stores data. It is a way data is organized in memory. They are implemented by template classes and therefore can be easily customized to hold different types of data.
- An algorithm: is a procedure that is used to process the data contained in the containers. They are implemented by template functions.
- An iterator: is an object that points to an element in a container. We can use iterators to move through the contents of containers.
QUESTION 4
a) List and explain three types of programming errors [6 Marks]
- Logic error – Occur due to poor understanding of the problem and solution procedure.
- (^) Syntactic error - Arise due to poor understanding of the language itself.
- Exceptions - runtime anomalies or unusual conditions that a program may encounter while executing.
b) Explain the following terms in exceptions handling mechanism
[6 Marks]
b)..i Hit the exception - Find the problem
b)..ii Throw an exception - Inform that an error has occurred
b)..iii Catch the exception - Receive the error information
b)..iv Handle the exception - Take the corrective action
c) Explain the concept of templates. Differentiate between function and class
templates [4 Marks]
- Templates make it possible to use function or class to handle many different data types.
- 2 categories of templates are - functions and classes templates.
- (^) Function template is a pattern, or blueprint, for making many functions
- Class templates are generally used for data storage (container) classes.
d) Explain the term namespace [4 Marks]
- Namespaces allow group entities like classes, objects and functions under a name.
The format of namespaces is:
namespace identifier
{
Entities;
}
To avoid use of goto tightly controlled looping commands have been introduced: for, while, do---while. Use of goto is always a sign of bad design. Avoid using it.
c) Using a simple diagram show an example of an inheritance hierarchy for university
community members. [6 Marks]
End of Exam
