SMU C++ SLM UNIT 1

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OOPS Using C++ Unit 1

Sikkim Manipal University Page No. 1

Unit 1 Introduction to OOP and C++

Structure

1.1 Introduction

1.2 Evolution of Programming methodologies

Self Assessment Questions

1.3 Introduction to OOP and its basic features


1.4 Basic components of a C++ Program and program structure

Self Assessment Questions1.5 Compiling and Executing C++ Program


Summary

Terminal Questions

1.1 Introduction

This unit has the following objectives

To understand the importance of object oriented programming approach

over procedural languages

To learn the basic features supported by OOP languages

To learn the basic construct of a C++ program and learn to compile and

execute it

1.2 Evolution of Programming methodologies

The programming languages have evolved from machine languages,assembly languages to high level languages to the current age of

programming tools. While machine level language and assembly language

was difficult to learn for a layman, high level languages like C, Basic, Fortran

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and the like was easy to learn with more English like keywords. These

languages were also known as procedural languages as each and everystatement in the program had to be specified to instruct the computer to do

a specific job. The procedural languages focused on organizing program

statements into procedures or functions. Larger programs were either

broken into functions or modules which had defined purpose and interface

to other functions.

Procedural approach for programming had several problems as the size of

the softwares grew larger and larger. One of the main problems was data

being completely forgotten. The emphasis was on the action and the data

was only used in the entire process. Data in the program was created by

variables and if more than one functions had to access data, global

variables were used. The concept of global variables itself is a problem as it

may be accidentally modified by an undesired function. This also leads to

difficulty in debugging and modifying the program when several functions

access a particular data.

The object oriented approach overcomes this problem by modeling data and

functions together there by allowing only certain functions to access the

required data.

The procedural languages had limitations of extensibility as there was

limited support for creating user defined datatypes and defining how these

datatypes will be handled. For example if the programmer had to define his

own version of string and define how this new datatype will be manipulated,

it would be difficult. The object oriented programming provides this flexibility

through the concept of class.

Another limitation of the procedural languages is that the program model is

not closer to real world objects . For example, if you want to develop a

gaming application of car race, what data would you use and what functions

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you would require is difficult questions to answer in a procedural approach.

The object oriented approach solves this further by conceptualizing theproblem as group of objects which have their own specific data and

functionality. In the car game example, we would create several objects

such as player, car, traffic signal and so on.

Some of the languages that use object oriented programming approach are

C++, Java, Csharp, Smalltalk etc. We will be learning C++ in this text to

understand object oriented programming. C++ is a superset of C. Several

features are similar in C and C++.


1. List the limitations of procedural languages

2. _______ is an OOP Language

3. In OOP approach programmers can create their own data types.

True/False

4. In procedural languages, the programs are written by dividing the

programs into smaller units known as __________

1.3 Introduction to OOP and its basic features

As discussed earlier, one of the basic concept in Object Oriented

Programming approach is bundling both data and functions into one unit

known as object. The functions of a particular object can only access the

data in the object providing high level of security for the data. The functions

in the object are known as member functions or sometimes as methods.

The key features of OOP programming languages are:

Objects and Classes

An Object is a program representation of some real-world thing (i.e

person, place or an event). Objects can have both attributes(data) and

behaviours (functions or methods). Attributes describe the object with

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respect to certain parameters and Behaviour or functions describe the

functionality of the object.

Table 1.1 Example of Objects

Polygon Object Bank Account

Attributes

Position

Fill Color

Border color

Behaviour

Move

Erase

Changecolor

Attributes

Accountnumber

Balance

Behaviour

Deduct Funds

Transferfunds

DepositFunds

Showbalance

According to Pressman, Objects can be any one of the following:

a) External entities

b) Things

c) Occurrences or events

d) Roles

e) Organisational units

f) Places

g) Data Structures

For example, objects can be an menu or button in an graphic user interface

program or it may be an employee in an payroll application. Objects can

also represent a data structure such as a stack or a linked list. It may be a

server or a client in an networking environment.

Objects with the same data structure and behavior are grouped together as

class. In other words, Objects are instances of a class. Classes are

templates that provide definition to the objects of similar type. Objects are

like variables created whenever necessary in the program. For example,

Employee may be a class and Pawan, Sujay and Ganesh are objects of the

class employees. Just as you can create as many variables of a default

datatype such as integer, you can create as many objects of a class.

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Classes and Objects support data encapsulation and data hidingwhich are

key terms describing object oriented programming languages. Data andfunctions are said to be encapsulated in an single entity as object. The data

is said to be hidden thus not allowing accidental modification.

Inheritance

Inheritance is one of the most powerful feature of Object Oriented

Programming Languages that allows you to derive a class from an

existing class and inherit all the characteristics and behaviour of the

parent class. This feature allows easy modification of existing code and

also reuse code. The ability to reuse components of a program is an

important feature for any programming language

Polymorphism and Overloading

Operator overloading feature allows users to define how basic operators

work with objects. The operator + will be adding two numbers when

used with integer variables. However when used with user defined string

class, + operator may concatenate two strings. Similarly same functions

with same function name can perform different actions depending upon

which object calls the function. This feature of C++ where same

operators or functions behave differently depending upon what they are

operating on is called as polymorphism (Same thing with different forms).

Operator overloading is a kind of polymorphism.

OOP approach offers several advantages to the programmers such as

Code can be reused in situations requiring customization

Program modeling and development closer to real world situations and

objects

Easy to modify code

Only required data binded to operations thus hiding data from unrelated

functions

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1. _____________ feature in OOP allows to reuse code.2. The concept of bundling data and functions into single unit is termed as

___________

3. Object is an __________ of a class

4. Give an example of a class and an object

5. ______________ is an advantage of OOP approach

1.4 Basic components of a C++ Program and program structure The C++ is a superset of C. At the basic level, the programs look similar in

both C and C++. Every statement in C++ ends with a semicolon (). All the

reserved words have to be written in small case and the c++ compiler is

case sensitive. Data in programming languages are stored in variables. To

create a variable, the variable should support an inbuilt datatype. The

variable is a name given to a particular location in the memory and the value

stored in a variable can be altered during program execution. The datatypes

supported in C++ are listed below

Table 1.2 Basic Datatypes in c++

Data Type Size (in bytes) Values that can be taken

Int 2 -32768 to 32767

Bool 1 False and true / 0 and 1

Char 1 -128 to 127

Long 4 -2,147,483,648 to 2,147,483,647

Float 4 3.4 X 10-38

to 3.4 X 1038

(Precision 7)

Double 8 1.7 X 10-308 to 1.7 X 10308 (Precision 15)

Long double 10 3.4 X 10-4932 to 1.1 X 104932 (Precision 19)

Unsigned int 2 0 to 65,535

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Variables can be named according to following rules

Can comprise of 1 to 8 alphabets, digits or underscore

First character should be an alphabet

Names are case sensitive

Reserve words of c++ cannot be used

Variables have to be declared before using them in the program. The

declaration is done in the following way:

datatype variablename

Eg: int data

The above declaration declares a integer variable named data. The value

stored in int data by default is a junk value. Values can also be assigned to

the variable during declarations or initialized separately using the

assignment operator =.

Eg: int data=0

Or

int data

data=0

Constants are those which do not change during execution of a program.

The constants in C++ can be numeric, character or string constants.

Examples of each are shown in table 1.3

Table 1.3 Example of Constants

Constant Example Constraints

NumericConstant

23000

450.6 (Floating point)

Can be negative or positive, cannotcontain blanks or commas, or $

Character

Constant

A Any character enclosed within single

quotes, represented by unique ASCIInumber in the memory

String Constant Hello Set of characters enclosed in doublequotes, last character in the string isnull character \0

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Operators supported in C++ are listed below. Unary operators are used with

one operand and binary operator is used with two operands.

Table 1.4 Operators in C++

Arithmetic Operators Type Action

- Unary aswell asbinary

Subtraction for binary and minus forunary

+ Binary Addition

* Binary Multiplication

/ Binary Division

% Binary Modulus (remainder after dividing)-- Unary Decrement value by one

++ Unary Increment value by one

Relational Operators Type Action

> Binary Greater than

>= Binary Greater than or equal

< Binary Less than

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sum=a+b

cout

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two integers. The values entered by the user is then stored in the variables

a and b. Each variable in cin statement should separated by >> operator.

Comment statements can be included in the program by prefixing the

statement with // for single line comments. Comments add clarity to the

program. Multiple line comments can be added by enclosing the statements

between /* and */.


1. ______________ is a header file used in c++ that handles input and

output functions.

2. ____________ statement is used to input data from the user in c++.

3. ______________ statement is used to display data on the display

screen in c++.

4. ______________ is a master function required in all C++ program and

program execution begins from the first statement of this function.

1.5 Compiling and Executing C++ Program

1. There are three steps in executing a c++ program: Compiling, Linkingand Running the program. The c++ programs have to be typed in a

compiler. All the programs discussed in the book will be compiled on

turbo c++ compiler. The turbo c++ compiler comes with an editor to type

and edit c++ program. After typing the program the file is saved with an

extension .cpp. This is known as source code. The source code has to

be converted to an object code which is understandable by the machine.

This process is known as compiling the program. You can compile your

program by selecting compile from compile menu or press Alt+f9. Aftercompiling a file with the same name as source code file but with

extension .obj. is created.

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Second step is linking the program which creates an executable file .exe

(filename same as source code) after linking the object code and thelibrary files (cs.lib) required for the program. In a simple program, linking

process may involve one object file and one library file. However in a

project, there may be several smaller programs. The object codes of

these programs and the library files are linked to create a single

executable file. Third and the last step is running the executable file

where the statements in the program will be executed one by one.

Fig 1.1 shows the entire process. When you execute the program, the

compiler displays the output of the program and comes back to theprogram editor. To view the output and wait for user to press any key to

return to the editor, type getch() as the last statement in the program.

Getch() is an inbuilt predefined library function which inputs a character

from the user through standard input. However you should include

another header file named conio.h to use this function. Conio.h contains

the necessary declarations for using this function. The include statement

will be similar to iostream.h.

Fig. 1.1: Compiling and Linking

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During compilation, if there are any errors that will be listing by the compiler.

The errors may be any one of the following1. Syntax error

This error occurs due to mistake in writing the syntax of a c++ statement

or wrong use of reserved words, improper variable names, using

variables without declaration etc. Examples are : missing semi colon or

paranthesis, type integer for int datatype etc. Appropriate error message

and the statement number will be displayed. You can see the statement

and make correction to the program file, save and recompile it.

2. Logical errorThis error occurs due to the flaw in the logic. This will not be identified by

the compiler. However it can be traced using the debug tool in the editor.

First identify the variable which you suspect creating the error and add

them to watch list by selecting Debug ->Watches->Add watch. Write the

variable name in the watch expression. After adding all the variables

required to the watch list, go to the statement from where you want to

observe. If you are not sure, you can go to the first statement of the

program. Then select Debug ->Toggle Breakpoint (or press ctrl + f8). Ared line will appear on the statement. Then Run the program by

selecting Ctrl + f9 or Run option from run menu. The execution will halt

at the statement where you had added the breakpoint. The watch

variables and their values at that point of time will be displayed in the

bottom in the watch window. Press F8 to execute the next statement till

you reach the end of the program. In this way you can watch closely the

values in the watch variables after execution of each and every

statement in the program. If you want to exit before execution of the laststatement press Ctrl + Break. To remove the breakpoint in the program

go to the statement where you have added breakpoint select Debug -

>Toggle Breakpoint (or press ctrl + f8). Select Debug -> watch ->remove

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watches to remove the variables in the watch list. This tool helps in

knowing the values taken by the variable at each and every step. Youcan compare the expected value with the actual value to identify the

error.

3. Linker error

This error occur when the files during linking are missing or mispelt

4. Runtime error

This error occurs if the programs encounters division by zero, accessing

a null pointer etc during execution of the program


1. ___________, ______________ and _____________ are phases in

execution of a C++ program

2. The logical error is identified by the compiler. True/False

3. ________________ is the extension of C++ program source files

4. ________________ is the extension of C++ object code

Summary

Object oriented Programming enables storing data and functions togetherwhich enables hiding data from unnecessary exposure. Procedural

languages differs from the Object oriented programming in the approach

used in solving the problem. While the former focuses on organizing

programs around functions, the later focuses organizing programs around

classes. Classes allow users to define their own datatypes and functionality.

This allows extension of the basic datatypes supported by the language.

Reusability of code through inheritance allows users to use the existing

code without modifying it but also extend the functionality of the existing

code. The C++ programs are similar to C except for the object orientedprogramming features. Every C++ program has a main function from where

the execution starts. C++ programs goes through two phases ie compiling

and linking before execution.

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Terminal Questions

1. Which of the following is not a feature of Object Oriented Programminga. Data encapsulation b. Inheritance c. Operator Overloading

d. Data Structure

2. Which one of the following is not an inbuilt basic datatype in c++

a. Int b. Bool c. String d.Float

3. Write a program that accepts two numbers from the user and swaps the

two numbers without using a temporary variable.

4. Write a program that accepts two numbers a and b and divides a by b

and displays the quotient and the remainder.

5. Object constitutes of ____________ and _____________

Answers to SAQs and TQs

Answers to SAQs in 1.2

1. Limitations of procedural languages are no importance to data and

inability to define user defined datatypes and define functionality for the

same

2. C++, smalltalk, Java are all OOP Languages

3. True

4. Functions or procedures


1. Inheritance

3. Data Abstraction

4. Object is an instance of a class

5. Class - car and object Maruti 800

6. Reusability of code


1. iostream.h2. cin

3. cout

4. main() function

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1. Compiling, Linking and Running2. False, it can assist in identifying using debug tool

3. .cpp

4. .obj

Answers TQs

1. d

2. c

3. Program to swap two numbers without using a temporary variable

# include

void main()

{ int num1,num2

cout num1>>num2

Num1=num1+num2

Num2=num1-num2

Num1=num1-num2

cout

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