He Dieu Hanh

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CSE 459.22 Programming in C++
Name: Ren-Shiou Liu
Time: R 8:30am-9:18am
Room: BO 0124
E-mail: [email protected]
Office: DL 285
Office hours: T 2:30pm-4:30 (tentative)
Webpage: http://www.cse.ohio-state.edu/rsliu/459.22
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Overview
Sign the roster list
Syllabus and Course Policies
Introduction to C++
About Lab 1
Fill Questionnaire
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What is programming?
Programming is taking
A problem
Find the area of a rectangle
A set of data
length
width
A set of functions
area = length * width
Then,
Applying functions to data to solve the problem
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Programming Concept Evolution
Unstructured
Procedural
Object-Oriented
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Procedural Programming
The main program coordinates calls to procedures and hands over appropriate data as parameters.
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Procedural Concept (II)
Procedural Languages
C, Pascal, Basic, Fortran
Facilities to
Pass arguments to functions
Return values from functions
For the rectangle problem, we develop a function
int compute_area (int l, int w){
return ( l * w );
}
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Object-Oriented Concept
Objects of the program interact by sending messages to each other
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Objects
An object is an encapsulation of both functions and data
Objects are an Abstraction
represent real world entities
Classes are data types that define shared common properties or attributes
Objects are instances of a class
Objects have State
have a value at a particular time
Objects have Operations
associated set of operations called methods that describe how to carry out operations
Objects have Messages
request an object to carry out one of its operations by sending it a message
messages are the means by which we exchange data between objects
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OO Perspective

Let`s look at the Rectangle through object oriented eyes:
Define a new type Rectangle (a class)
Data
width, length
Function
area()
Create an instance of the class (an object)
Request the object to return its area

In C++, rather than writing a procedure, we define a class that encapsulates the knowledge necessary to answer the question - here, what is the area of the rectangle.
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Example Code
class Rectangle
{
private:
int width, length;
public:
Rectangle(int w, int l)
{
width = w;
length = l;
}
main()
{
Rectangle rect(3,5);
cout<}
int area()
{
return width*length;
}
}
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Encapsulation
class Circle
{
private:
int radius
public:
Circle(int radius);

// The area of a circle
int area();
};
class Triangle
{
private:
int a, b, c;
public:
Triangle (int a, int b, int c);

// The area of a triangle
int area();
};
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Abstract Types
class Shape
{
public:
Shape();

// Calculate the area for
// this shape
virtual int area() = 0;
};
Decouple the interface from the representation and give up genuine local variables
virtual means “may be redefined later in a class derived from this one”
“= 0” means pure virtual
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Inheritance and Polymorphism
class Circle : public Shape
{
private:
int radius
public:
Circle (int radius);
int area();
};
class Triangle : public Shape
{
private:
int a, b, c;
public:
Triangle (int a, int b, int c);
int area();
};
int sum_area(Shape s1, Shape s2) {
return s1.area() + s2.area(); // Example of polymorphism
}
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Characteristics of OOPL
Encapsulation: Combining data structure with actions
Data structure: represents the properties, the state, or characteristics of objects
Actions: permissible behaviors that are controlled through the member functions
Data hiding: Process of making certain data inaccessible
Inheritance: Ability to derive new objects from old ones
permits objects of a more specific class to inherit the properties (data) and behaviors (functions) of a more general/base class
ability to define a hierarchical relationship between objects
Polymorphism: Ability for different objects to interpret functions differently
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Basic C++
Inherit all ANSI C directives
Inherit all C functions
You don’t have to write OOP programming in C++
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Basic C++ Extension from C
comments
/* You can still use the old comment style, */
/* but you must be // very careful about mixing them */
// It`s best to use this style for 1 line or partial lines
/* And use this style when your comment
consists of multiple lines */
cin and cout (and #include )
cout << "hey";
char name[10];
cin >> name;
cout << "Hey " << name << ", nice name." << endl;
cout << endl; // print a blank line
declaring variables almost anywhere
// declare a variable when you need it
for (int k = 1; k < 5; k++){
cout << k;
}
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Basic C++ Extension from C (II)
const
In C, #define statement
Preprocessor - No type checking.
#define n 5
In C++, the const specifier
Compiler - Type checking is applied
const int n = 5; // declare and initialize
New data type
Reference data type “&”.
int ix; /* ix is "real" variable */
int & rx = ix; /* rx is “alias” for ix. Must initialize*/
ix = 1; /* also rx == 1 */
rx = 2; /* also ix == 2 */
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C++ - Advance Extension
C++ allows function overloading
In C++, functions can use the same names, within the same scope, if each can be distinguished by its name and signature
The signature specifies the number, type, and order of the parameters expressed as a comma separated list of argument types

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C++
Is a better C
Expressive
Supports Data Abstraction
Supports OOP
Supports Generic Programming
Containers
Stack of char, int, double etc
Generic Algorithms
sort(), copy(), search() any container Stack/Vector/List
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Take Home Message
There are many different kinds of programming paradigms, OOP is one among them.

In OOP, programmers see the execution of the program as a collection of dialoging objects.

The main characteristics of OOPL include encapsulation, inheritance, and polymorphism.

Don’t panic if you don’t understand the materials for the first class. Things will become clear in time.