Object Oriented Programming using C++ Part I

OOP/AKN/Part_I/1
Object Oriented Programming
using C++
Module I
Ajit K Nayak, Ph.D.
SOA University, Odisha, India

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Contents
1. 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

OOP/AKN/Part_I/8
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 review
C++ 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 arithmetic
types
 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 program
int 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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Namespace
What 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:
&ii
pp:
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?

OOP/AKN/Part_I/34
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 Arguments
Parameters 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 Overloading
A 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 Functions
Every 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));

OOP/AKN/Part_I/44
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

OOP/AKN/Part_I/46
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 write
int* ip;
ip = new int;
...
delete ip;

OOP/AKN/Part_I/49
Dynamic Memory Allocation
In C we write (for multiple values)
int* ip;
ip = (int*)malloc(sizeof(int) * 100);
…
free ip;
In C++ we will write
int* ip;
ip = new int[100];
...
delete [ ] ip;

OOP/AKN/Part_I/50
New/Delete opearators
int* 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 Leak
 Memory 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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Readings
Programming
 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

Object Oriented Programming using C++ Part I

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Object Oriented Programming using C++ Part I