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Course Code : CS 72 Course Title : C++ and Object Oriented Programming Assignment Number : BCA (6)-72/Assignment/ 11 Maximum Marks : 100 (Weightage 25%) Last Date of Submission : 30th April, 2011/30th October, 2011 www.bronzeacademy.com, [email protected]
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There are seven questions in this Assignment. Answer all the questions. You may use illustrations and diagrams to enhance your explanations. Please go through the guidelines regarding assignments given in the Programme Guide for the format of presentation. Answer to each part of the question should be confined to about 300 words. Question 1: Explain the term Class and Object using the example of a student class. The student class represents name, enrolment number, father’s name, telephone number, program code and date of birth of a student. The class has a function to show the information about the student except date of birth, and to modify the information of telephone number and program. List the private and public members (data members as well as member functions) for the class student. Define the data types of member variables using C++ and create few objects of the class. Can you put information in those objects? Give reasons.
(8 Marks) OBJECTS
Objects are the basic run-time entities in an object-oriented system. They may represent a person, a place, a bank account, a table of data or any item that the program has to handle. They may also represent user-defined data such as vectors, time and lists. Programming problems is analyzed in terms of objects and the nature of communication between them. Program objects should be chosen such that they match closely with the real-world objects. Objects take up space in the memory and have an associated address like a record in Pascal, or a structure in C. When a program is executed, the objects interact by sending messages to one another. For example, if “customer” and “count” are two objects in a program, then the customer object may send a message to the account object requesting for the bank balance. Each object contains data, and code to manipulate the data. Objects can interact without having to know details of each other’s data or code. It is sufficient to know the type of message accepted, and the type of response return by the objects. Although different authors represent them differently, Fig shows two notations that are popularly used in object-oriented analysis and design.
Display
Average
Total STUDENT Object:STUDENT
FUNCTIONS Total Average Display
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DATA Name Date-of-birth Marks
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CLASSES We just mentioned that objects contain data, and code to manipulate that data. The entire set of data and code of an object can be made a user-defined data type with the help of a class In fact, objects are variables of the type class. Once a class has been defined, we can create any number of objects belonging to that class. Each object is associated with the data of type class with which they are created. A class is thus a collection of objects of similar type. For example, mango, apple and orange are members of the class fruit. Classes are user-defined data types and behave like the built-in types of a programming language. The syntax used to create an object is no different than the syntax used to create an integer object in C. if fruit has been defined as a class, then the statement Fruit mango; Will create an object mango belonging to the class Fruit Example #include<iostream.h> #include<conio.h> #include<string.h> class Student { private: //default char *name; long enrolment_number; char *father_name; long phone; char *pro_code; char *dob; public: Student(char *n,long e,char *f,long p,char *pc,char *d) { strcpy(name,n); enrolment_number=e; strcpy(father_name,f); phone=p; strcpy(pro_code,pc); strcpy(dob,d); } void show() { cout<<"\nName\t\t"<<name; cout<<"\nEnrolment\t"<<enrolment_number; cout<<"\nFather\'s Name\t"<<father_name; cout<<"\nPhone\t\t"<<phone; cout<<"\nProgram Code\t"<<pro_code; } void change_phone(long new_phone) { phone=new_phone; }
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}; void main() { clrscr(); Student x("Rahul",101,"Ram",234,"BCA","June 12"); x.change_phone(900); x.show(); Student y("Rohit",102,"Hemant",434,"MCA","March 13"); getch(); }
Question 2: Explain the following terms in the context of object oriented programming using the student class of question 1. You must use C++ to define the student class. In addition, assume that the student class has a sub class namely “PhD Student” who has an additional field “Department”. The function to show the information about PhD student also prints the department in addition to showing the information as shown by the student class.
(28 Marks) (a) Overloaded Constructors (b) Encapsulation The wrapping up of data and functions into a single unit (called class) is known as encapsulation. Data encapsulation is the most striking feature of a class. The data is not accessible to the outside world, and only those functions which are wrapped in the class can access it. These functions provide the interface between the object’s data and the program. This insulation of the data from direct access by the program is called data hiding or information hiding. (c) Inheritance Inheritance is the process by which objects of one class acquire the properties of objects of another class. It supports the concept of hierarchical classification. For example, the bird ‘robin’ is a part of the class ‘flying bird’ which is again a part of the class ‘bird’. The principle behind this sort of division is that each derived class shares common characteristics with the class from which it is derived as illustrated in Fig. In OOP, the concept of inheritance provides the idea of reusability. This means that we can add additional features to an existing class without modifying it. This is possible by deriving a new class from the existing one. The new class will have the combined features of both the classes. The real appeal and power of the inheritance mechanism is that it allow the programmer to reuse a class that is almost, but not exactly, what he wants, and to tailor the class in such a way that it does not introduce any undesirable side-effects into the rest of the classes. Note that each sub-class defines only those features that are unique to it. Without the use of classification, each class would have to explicitly include all of its features.
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Vehicles
Two wheeler Four wheeler
Bikes Scooters Personal Commercial
(d) Polymorphism Polymorphism is another important OOP concept. Polymorphism, a Greek term, means the ability to take more than one form. An operation may exhibit different behaviours in different instances. The behaviour depends upon the types of data used in the operation. For example, consider the operation of addition. For two numbers, the operation will generate a sum. If the operands are strings, then the operation would produce a third string by concatenation. The process of making an operator to different behaviours in different instances is known as operator overloading. Figure illustrates that a single function name can be used to handle different number and different types of arguments. This is something similar to a particular word having several different meanings depending on the context. Using a single function name to perform different types of tasks s known overloading. Polymorphism plays an important role in allowing objects having different internal structures to share the same external interface. This means that a general class of operations may be accessed in the same manner even though specific actions associated with each operation many differ. Polymorphism is extensively used in implementing inheritance.
Shape
Draw()
Box object Triangle object Circle object
Draw(circle) Draw(box) Draw(triangle)
Question 3: What are the advantages of using UML? Create the class diagram for a University having classes – Student, Teacher, Subject and Programme. Make suitable assumptions, if any.
(8 Marks)
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Question 4: Explain the usage of the following C++ operators with the help of an example program. (8 Marks) (a) operator for type casting C++ permits explicit type conversion of variables or expression using the type cast operator. Traditional C casts are augmented in C++ by a function-call notation as a syntactic alternative. The following two versions are equivalent: (type-name) expression Examples: average = sum/float(i); A type-name behaves as if it is a function for converting values to a designated type. The function-call notation usually leads to simplest expressions. However, it can be used only if the type is an identifier. For example, p = int * (q); (b) operator for bitwise OR Bitwise OR operator which is represented as |. The rules that govern the value of the resulting bit obtained after ORing of two bits is shown in the truth table below.
Condtion1 Condition2 Result (|) 0 0 0 0 1 1 1 0 1 1 1 1
(c) operator for dereferencing an address The dereference operator * takes a pointer to a value (variable or object) and returns the value. For example:- Int_t my_int = 2; Int_t *my_int_ptr = &my_int; *my_int_ptr = 4; my_int_ptr is a pointer to my_int. By dereferencing the pointer my_int is retrieved. In this example it is then assigned to so my_int receives the value 4.
See operator precedence
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Other Uses for *
1. When * after a type name (either a basic data type or a class) it means the the type is a pointer to that type, as shown in the above declaration of my_int_ptr. The logic is that the declaration:-
2. Int_t *my_int_ptr;
states that *my_int_ptr is an Int_t, from which it follows that my_int_ptr must be a pointer to Int_t
3. * is also an arithmetic operator.
(d) comma operator
In the C++ programming languages, the comma operator (represented by the token ,) is a binary operator that evaluates its first operand and discards the result, and then evaluates the second operand and returns this value (and type). The comma operator has the lowest precedence of any C operator, and acts as a sequence point.
The use of the comma token as an operator is distinct from its use in function calls and definitions, variable declarations, enum declarations, and similar constructs, where it acts as a separator.
In this example, the differing behavior between the second and third lines is due to the comma operator having lower precedence than assignment.
int a=1, b=2, c=3, i; // comma acts as separator in this line, not as an operator i = (a, b); // stores b into i ... a=1, b=2, c=3, i=2 i = a, b; // stores a into i. Equivalent to (i = a), b; ... a=1, b=2, c=3, i=1 i = (a += 2, a + b); // increases a by 2, then stores a+b = 3+2 into i ... a=3, b=2, c=3, i=5 i = a += 2, a + b; // increases a by 2, then stores a = 5 into i ... a=5, b=2, c=3, i=5 i = a, b, c; // stores a into i ... a=5, b=2, c=3, i=5 i = (a, b, c); // stores c into i ... a=5, b=2, c=3, i=3
A handy reminder is that
(a, b)
has the same effect as using C's ternary operator like
(a ? b : b)
Because the comma operator discards its first operand, it is generally only useful where the first operand has desirable side effects, such as in the initialiser or increment statement of a for loop. For example, the following terse linked list cycle detection algorithm (a version of Floyd's "tortoise and hare" algorithm):
bool loops(List *list) { List *tortoise, *hare; /* advance hare 2 times faster than tortoise */ for (tortoise = hare = list;
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hare && (hare = hare->next); /* tests for valid pointers + one step of hare */ tortoise = tortoise->next, hare = hare->next) /* comma separates hare and tortoise step */ if (tortoise == hare) /* loop found */ return true; return false; }
Question 5: Differentiate between call by value and call by reference with the help of an example in the content of function call. Explain the advantages of call by value. What does C++ uses?
(8 Marks) Function can accept any type of argument you want. You just need to give the argument a name and a data type, just like you would a local variable. In fact, arguments are just local variables that happen to be declared on the same line as the procedure name. You can use two different methods for passing in parameters to procedure: call by value call by reference. Ther’s a big difference between these two methods, as you’ll see in this section. Recall that the parameters that appear in the definition of a function are called formal parameters.
CALL BY VALUE The call by value method copies the values of actual parameters into the formal parameters, that is, the procedure crates its own copy of argument values and then uses them. To understand this concept, let us consider one example. To test your grammar, your English Teacher purposely writes grammatically incorrect passage on her sheet and gives it to you for corrections. So you copy down the given passage on your own sheet and make corrections there. This is an example of call by value method. Here, your teacher passes the sheet having grammatically incorrect passage (which is the actual parameter here) to you, you copy the passage on your sheet (this is the formal parameter). Whatever changes take place, are not reflected back to the orginal as the value of original is copied onto another which is the work coy. Thus, in call by value method, the changes are not reflected back to the original values. In C++, to pass arguments by value, you don’t need to mention any keyword when declaring arguments as shown below: void byValFunction(int x){ : : } Only a copy of a variable is passed when an argument is passed by value. If the procedure changes the value, the change affects only the copy and not the variable itself.
CAL BY REFERENCE In the call by reference method, the called procedure does not create its own copy of original values, rather, it refers to the original values only by different names i.e. the references. Thus the called procedure works with the original data and any change in the values gets reflected to the data. To understand this concept, let us revise our same old example of grammatically
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incorrect passage. if your English teacher gives you the original sheet having the grammatically incorrect passage and allows you to work upon the same sheet, then whatever correction you make, will be there on the original. In other words, I can say the changes are reflected back to the original as the value of the original is not copied anywhere rather original itself has been made the work copy. Thus, in call by reference method, the original is not copied anywhere rather original itself has been made the work copy. Thus, in call by reference method, the changes are reflected back to the original values. The call by reference method is useful in situation where the values of the original variables are to be changed using a function.
(i) Mention *,& operator in the argument definition.
void byRefFunction(int *x) { } If you specify a data type for an argument passed by reference, you must pass value of that type for the argument. You can work around this by passing an expression, rather than a data type, for an argument. C++ evaluates an expression and passes it as the required type if it can. Example void refFun(int *x) { *x=100; //value at operator } void valFun(int x) { X=100; } void main() { int a=10,b=10; refFun(a); valFun(b); cout<<a<<b; } Question 6: Write a template class “binaryTree” in C++. The class should have functions for search and insert and element into a binaryTree. Use this template to create a binary tree of integer keys. Make suitable assumptions, if any.
(20 Marks) Question 7: Create a class AlphaString that stores only alphabets in a string of arbitrary length. The string has a constructor that makes sure that String has only Alphabets. The class also has a copy constructor, and an overloaded + operator. The overloaded + operator should perform the
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concatenation of two strings. Does the class need an explicit destructor? Justify your answer.
(20 Marks)
