Object Oriented Programming using C++ Part I

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Object Oriented Programming

using C++

Module I

Ajit K Nayak, Ph.D.

SOA University, Odisha, India

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Contents1. Fundamentals

2. Simple Program

3. Operators

4. Datatypes

5. Namespace

6. Function Prototypes

7. References

8. Passing Default Arguments

9. Function Overloading

10. Inline Functions

1. Named constants

2. Dynamic memory allocations

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Motivation

OOD is the current technology for software

design and development.

C++ is a tool to develop programs/codes for

OOP.

Therefore, this subject is the bread and

butter for all those are interested in Software

Industry.

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About the Course

Two Goals for this course(OO-P)

Understand OO

Thinking in Objects

Familiar with P

Programming in C++

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Course Description

In this course:

C++ is used for illustrating and

implementing Object Oriented concepts.

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A Sample Program/*Author : Ajit K Nayak

Reg #:

Date:

Source file: helo.cpp

Desc: A Simple Hello, World Program

*/

#include <iostream>

using namespace std;

main() {

/* the output statement */

cout << “Hello, World!”<<endl;

}

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How to Write and Execute in Linux

Open a file in vi / gedit with extension as

.cpp or .cxx or .C

Write the source code

Save and exit

Compile with c++ <filename> (or g++)

Check for errors

Execute with ./a.out

Guideline:- Do write the source code in well

indented format

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History of C and C++

C (K & R-70s) was evolved from BCPL(M.

Richards-67) and B(K. Thompson-70).

C++ is developed by Bjarne Stroustrup in

1980

C++ is an extension to C

latest standard C++11 ISO/IEC 14882:2011

Along with C-style programming it provides

capabilities for OOP

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The Creator

http://www.research.att.com/~bs/homepage.html

Bjarne

Stroustrup

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Guidelines…B.Stroustrup

Knowing C is not a prerequisite to learn C++

The better one Knows C, the harder it seems to be to avoid writing C++ in C-style.

Suggestions for C Programmers

Macros are almost never necessary

Don't Declare a variable before you need it

Don‟t use malloc(), use new operator

Try to avoid Void*, pointer arithmetic, unions and casts

Try thinking a program as a set of interacting agents represented as classes and objects

…

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Prerequisite

It is expected that you know:

branching: if – else, switch-case.

Loop: for, while, do- while.

Array, pointer, structure, function etc.

Not confident!!! Rush, pickup a C book learn and write programs on above topics.

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A Sample Program/*Author : Ajit K Nayak

Reg #:

Date:

Source file: helo.cpp

Desc: A Simple Hello, World Program

*/

#include <iostream>


main() {

//the output statement

cout << “Hello, World!”<<endl;

}

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Basic Operators- I Arithmetic operators ( +, -, *, /, % )

x = 5 % 2.5

Increment and decrement (++, --)

x = 3++;

Relational and comparison operators ( ==, !=, >, <, >=, <= ) x

= 5 > 3;

Logical operators ( !, &&, || )

Bitwise operators ( &, |, ^, ~, <<, >> )

x = 5 & 3

Compound assignment (+=, -=, *=, /=, %=, >>=, <<=, &=, ^=,

|=)

x = 3 * = 2

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Basic Operators- II Conditional ternary operator ( :? )

x = 7== 5 ? 4 : 3 ;

Comma operator ( , )

a = (b=3, b+2);

Explicit type casting operator

int i; float f = 3.14; i = (int) f;

Sizeof()

x = sizeof (char);

Precedence of Operators

x = 5 + 7 % 2;

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Operators specific to C++

Stream insertion (<<)

Stream extraction (>>)

Dynamic memory allocation: new, new[ ]

Memory de-allocation: delete, delete[ ]

Scope resolution (::)

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Datatypes …A reviewC++ has a set of fundamental types

Boolean type (bool)

Character type (char)

Integer type (int)

Floating point type (float)

Double precision type (double)

In addition a user can define

Enumeration type (enum)

to represent specific set of values

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Data types (contd.)There also is

A type void used to signify the absence of data

From these above types we can construct

Pointer type (*)

Array type ([ ])

Reference type (&)

Finally the most powerful user-defined types

Data structures and classes(struct, class)

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A Classification

Boolean, character, and integer types are collectively called as integral types

Floating point types are called arithmetictypes

Pointer, reference, and array are called associated/derived types

All of the above are built-in types

Enumerations, structures, and classes are called user defined types

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Boolean Type

A bool can have one of the two values;

true or false

It is used to express the results of logical expressions

Example:

bool b1=a==b;

b1=true ->if a and b are of same value

= false -> otherwise

bool greater(int a, int b){ return a>b; }

True has the value 1 and false has 0

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Boolean Type(contd)

Nonzero integers convert to true and 0 to false

More Examples

bool b = 7; // b is true

int i = true // i=1

bool x = a+b // true if ….

bool y = a|b // true if a or b is true

if (b) // if b is true

What is the size required to store a certain type?

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Example programint main(){

cout << "char: " << sizeof(char) << endl;

cout << "short: " << sizeof(short) << endl;

cout << "int: " << sizeof(int) << endl;

cout << "unsigned int: " << sizeof(unsigned int) << endl;

cout << "long int: " << sizeof(long int) << endl;

cout << "unsigned long int: " <<sizeof(unsigned long int)<< endl;

cout << "float: ” << sizeof(float)<<endl;

cout << "double: " << sizeof(double) << endl;

cout << "long double: " << sizeof(long double) << endl;

cout << "bool: " << sizeof(bool) << endl;

}

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NamespaceWhat is scope of a variable?

Outer

Block

{

int x=10;

…

{

int x=20;

…

}

…

}

Inner

Block

How to access

outer’s x and

Inner’s x?

If I can name the

blocks!

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Namespace contd.

C++ namespaces can be used to group names

together. (give a name to a block)

It provides a mechanism for expressing logical

grouping.

If some declarations logically belong together

according to some criteria, they may be put in a

common namespace

To use a namespace member, the member name

must be qualified with a namespace name and

the binary scope resolution operator

(namespace_name::member)

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Namespace contd.namespace outer{

int x=10;

namespace inner{

int x=20;

}

}

Scope resolution Operator

If there is a global variable???

main(){

int x=0;

cout<<“self "<<x;

cout<<"Out "<<outer::x;

cout<<"In "<<outer::inner::x;

}

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Namespace Contd.namespace mySpace{

int x=20;

int y=30,

int z=40;

}

To use these variables!

cout<< mySpace::x;

cout<< mySpace::y;

cout<< mySpace::z;

Another Way

using namespace mySpace;

cout<<x;

cout << y;

cout << z;

Note: cout and cin objects are

declared in predefined namespace

„std‟

Either write

using namespace std; or

std:: cout, std::cin etc.

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Function Prototype

main(){

int x = 5;

float y = 10.65;

doTask(x, y);

} //end of main

void doTask(int a, float b){

cout <<a+b<<„\n‟ ;

}//end of function

void doTask(int a, float b);Syntax:

• return_type <function_name>(data type of input parameter list separated by comma );

• It can be called as function declaration

• It is used at the time of compilation to check if the return value is handled correctly and correct number and type of arguments are passed to the function

• Never use a function without a prototype

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Call By Value

#include <iostream>


void increment(int);

main()

{

int i=2;

increment(i);

cout << “i = “ << i;

}

void increment(int x) { x++; }

OUTPUT ?

Explain!

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References

It is an alternative name for an object

It is used to specify arguments and return

values for functions in general and for

overloaded operators

Example

int i=1;

int& ir=i;

int x=ir;

ir=2;

//ir and i now refers to same value

// x=1

// i = 2

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References(contd.)

To ensure that a reference is a name for

something( bound to an object), we must

initialize the reference

Example:

int i=1;

int& r2;

Int& r1=i

//Error: initialization missing

//OK: r1 is now an alias for i

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Pointers and References

int ii = 0;

int& rr=ii;

rr++;

int *pp=&rr // or &ii

0

ii:

&iipp:

rr:

• pp is a variable which stores address of another variable

• rr is an alternative name (alias) for an existing variable

• The value of a reference cant be changed after initialization.

It always refers to the same object it was initialized. Which is

not the case in pointers

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Call By Reference

#include <iostream>


void increment(int &);

main(){

int i=2;

increment(i);

cout << “i =“ << i;

}

void increment(int& x) {

x++;

}

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Example2

#include <iostream>


int max(int&, int&);

main(){

int i=2,j=3;

cout<<max(i,j);

}

int max(int& x, int& y){

return x>y ? x:y;

}

Output?

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Example3#include <iostream>


int& max(int&, int&);

main(){

int i=2,j=3;

int &p=max(i,j);cout<<p; p=-30;

cout<<“i=“<i<„\t‟<<“j=“<<j<<„\t‟<<“p=“<<p

<<endl;

}

int& max(int &x, int &y){

return x>y ? x:y;

}Output?

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References contd.

Calls to functions that returns reference can be

put on the left side of the assignment operator.main(){

int i=2,j=3;

max(i,j)= -30;

cout<<“i=“<i<„\t‟<<“j=“<<j<<„\t‟<<endl;

}

The value –30 will be assigned to the larger of

i & j

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Use of passing by reference

To manipulate original values of variables

inside a function

To pass large objects

To return more than one value from a

function (virtually)

To use a function to the left side of =

operator

Any other, you may suggest!

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Default ArgumentsParameters can be assigned default values.

Parameters assume their default values when no actual parameters are specified for them in a function call.

A default argument is type checked at the time of function declaration and evaluated at the time of call

Default arguments may be provided for trailing arguments only

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Example// Find the sum of numbers in a range of values

// Between “lower” and “upper” using increment “inc”int sum(int lower,int upper=100,int inc=1){

int sum=0;

for(int k=lower; k<=upper; k+= inc)

sum += k;

return sum;

}

main(){

cout<<sum(1);

cout<<sum(1, 10);

cout<<sum(1, 10, 2);

}

Design a default argument function with its prototype!

//5050

//55

//25

Write the prototype for sum!!!

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Function OverloadingA function is said to be overloaded when the same

function name is used for different purposes.

It allows you to use the same name for different functions

void print(char);

void print(float);

Thus to overload a function we require to pass different types of arguments to each function with same name.

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Function Overloading(contd)

Compiler decides the function to be invoked using a

series of criteria in order

1. Exact match i.e. vol(5); int vol(int)

2. Match using integral promotions i.e. char to int, float to

double etc.

3. Match using standard conversions i.e. int to double,

double to long double

4. Match using user-defined conversions i.e. conversion

between user-defined types

5. Match using the ellipsis (…) i.e unspecified number of

arguments

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If more than one match is found, the call is rejected

by the compiler as ambiguous

Example

void print(int);

void print(const char*);

void print(double);

void print(long);

void print(char);

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void h(char c, int i, short s,float

f){

print(c);

print(i);

print(s);

print(f);

print(„a‟);

print(49);

print(0);

print(“a”);

}

// Exact match: print(char)

// Exact match: print(int)

// integral promotion:print(int)

// integral :print(double)

// Exact match: print(char)



// Exact :print(const char*)

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Overloading solely on return value is not allowed in C++

i.e. you cannot write

void f();

int f();

Task

Overload a function add( arg1, arg2) s.t. when both are

integers and doubles it produces the addition result,

when both are strings it produces another string by

concatenating both .

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Inline FunctionsEvery time a function is called, it takes a lot of

extra time due to

Jumping to function

Saving registers

Returning to calling function etc.

When a function is small, it becomes an

overhead

One solution is to use macros

#define max(a,b) ((a) > (b) ? (a):(b));

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Inline functions (contd.)But macros has various disadvantages(?)

An alternative in C++ is to use inline functions: inline int max(int a, int b) {

return (a > b ? a : b);

}

An Inline function is a function that is expanded in line when invoked.

The compiler inserts the equivalent function code at the place of invocation

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Macro vs Inline function#define square(x) x*x

main(){

cout<<square(3+2);

int y=3;

cout<<square(++y);

}

• Both fails, as macro is a blind replacement of statements.

• Unlike macros, inline functions may be declared any where in the program

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Named Constants

Only one method in C:

#define ArraySize 100;

//Macro constants

Another way in C++:

const ArraySize =100;

Again in C++:

constant can be used in local scope

const is often used when the value cannot be changed

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Examples of Using const

const int count = 5;

static const float average = 0.5;

const float f; //error!, invalid!

extern const float f; //ok, extern linkage

const int c3=myFunc(3); //ok, don‟t know the

//value at compile time

const int* p=&c2; //need to allocate space for c2

void (const int* p) { //cant modify *p here }

const int myFunc(int) // ok, but no use

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Dynamic Memory Allocation

In C we write (for a single value)int* ip;

ip = (int*)malloc(sizeof(int) );

…

free (ip);

In C++ we will writeint* ip;

ip = new int;

...

delete ip;

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Dynamic Memory Allocation

In C we write (for multiple values)int* ip;

ip = (int*)malloc(sizeof(int) * 100);

…

free ip;

In C++ we will writeint* ip;

ip = new int[100];

...

delete [ ] ip;

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New/Delete opearatorsint* p=new int; delete p;

int* p=new int(25);delete p;

int* p=new int[25];delete []p;

Task

Find a method to declare a multi-dimensional

array using new operator

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Memory LeakMemory leak:

when you do not free a block of memory allocated with

the new operator

or when you make it impossible to do so.

As a consequence your application may

eventually run out of memory and may even

cause the system to crash.

void func(){

char *ch;

ch = new char[100];

}

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Dangling Pointer Dangling pointer points to memory that has

already been freed. The storage is no longer

allocated. Trying to access it might cause a

Segmentation fault.

1. char* func() {

char str[10];

strcpy(str,"Hello!");

return(str);

}

2. int *c = new int; delete c;

*c = 3;

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ReadingsProgramming Bjarne Stroustrup, The C++ Programming Language, PE

Lippman, Lajoie, C++ Primer, Addison-Wesley

B. Eckel, Thinking in C++, Vol I and Vol II

Deitel & Deitel, C++ How to program

Schildt, C++ The complete reference

S. Sahay, OOP with C++

E. Balagurusami, Object oriented programming with C++

Concepts G.Booch, Object Oriented Analysis & Design

Bertand Meyer, Object Oriented Software Construction

Engineering

Object Oriented Programming using C++ Part I