Working with OOP synopsis concepts :- 

Based on the style of programming the languages are divided in to three types

Procedure   structure  OOPL

1960’s A! GOL                             1970’s

• No loops    COBOL
• No arrays   BASIC
• NO dynamic    ‘C’
• Memory allocation

 

Problems in C –language :-

P1

Main ()

{

Int Sal = 4000;

Print f (“%d”, Sal);

}

 

Output:-

~- 700

 

Problems :- 

1. Data types limits are not controlled at run time.

P2)

Main ()

{

Int I = 500 * 500/500;

Print f (“%d”, i);

}

 

Output :-

– 27

 

Problem 2 :- 

No proper implicit procedure for calculation

P3

Long Sal = 5000; // global variable

Main () {}

Void F1() {}

Void F2 () {}

Void Marketing Details ()

{

Long Sale = 500000;

Sale  = Sale + Sale ;
}

 

No Security for the  ‘DATA’

• To overcome all the these problems , ANSI (American National Standard Institute) defined a set of rules called as “OOPS”

 

When a language supports , the following oops concepts then that language is called as object oriented programming language (OOPL).

 

OOPS concepts :-

1. Encapsulation (Data Hiding)
2. Abstraction (Providing information)]
3. Polymorphism (overloading)
4. Inheritance

 

1. Encapsulation is a concept of data hiding.
2. Abstraction is a concept of providing full information a bout an entity (data binding)
3. Polymorphism is a concept of writing more than one function with same and different arguments.
4. Inheritance is a concept of deriving the features from base to derived class

 

 

OBS:

 

• To work with OOPS concepts, classes and object are required.
• Classes is a logical representation
• Object is a physical representation

 

As per .net , A classes is a collection of

1. Fields: private data of classes is called a field.
2. Properties: it defines the look and feel of an object
3. Methods: when an object can do do is called a method
4. Events: what user can do with an object is called an “event”

• Instance of a classes is called as an object

Instance means copy

 

Syntax to write a class:

 

Class C1 Name

{

Private int x,y;

Private String s;

Public void print ();

{

Return type

}

Private and public are assess specifiers   which provides scope of risibility

 

Syntax to create an object:-

 

Logical Diagram on class and object:-

 

 

Test obj = new Test()

 

• Object can access only public data.
• Object can not access private data

 

EX 1 :   on Classes and objects :-

Note :-

Classes must be declared in GD only.

• Open windows forms Application project
• Place a button
• Code in GD (Before button 1 click)

Classes Test

{

Private int x, y ; // fields    (or)  Reference types

Public void Read  (int a, int b) //a and b  are     value types, local variables.

{

x =a;

y =b;

}

Public void print ()

{

Int K = x +y ;

Message Box >show (“The sum is ” + K);

}//print

}//test

Code for Button 1 click

{

Test  t1 = new Test ()

T1.Read (10,20);

T1.Print (10,20);

T1.Print (); // output is ‘30’

Test  t2 = new Test ();

T2.print (); // output is ‘0’

Test t3  = new Test ();

T3.print (); //error

Test t3 = t1;

T3.print ();//output is ‘30’

}

Execute the project

OBS :-

1. Fields of a class are also called Instance variables.
2. In C#.net by default every class will be inherited from System. object class
3. System. object class contains four methods
4. Get Hash code ()
5. Get Type ()
6. Equals ()
7. To string ()
8. In C# .net every class contain minimum 4 methods.