Class and Object in C++

Class and Object in C++:

Class:

• Class is used to hold data members and member function i.e. variables and functions.
• It can be easily accessed anywhere and used to reduce the reusability of the code.

For example,

• Let’s take student,
• Student properties are all called as variables and student performance or student-related calculations(i.e. student result based on total and it may be pass or fail) are called as a function.

Where,

The student is a class.

Student properties (variables) : Roll_num,name,age,ect.

Student behaviours(function)  : total,average,result,fees details ect.

Note:

• If one or more variables declared within the class, called data members.
• If one or more functions declared in within the class, called member function.

Object:

• An object is used to access the members in the class.
• It simply said as the short name of the class.

Syntax:

1. <header files>
   class class_name //class declaration
   {
             Access specifiers:
             Variable_declaration;
             Method declaration or function_declaration()
             {
             //Statements
             }
   };
   void main()
   {
   //object declaration
   Class_name object_name;
   //accessing member function using object
   object_name .function_name();
   }

Note:

The class name and object name is a user-defined word.

Access specifiers:

• C++ access specifiers are used for determining or setting the boundary for the availability of class members (data members and member functions) beyond that class.

Types of access specifiers:

• Private – It is used to access the data member and member function within the classes.
• Public – It is used to access the data member and member function out of the class. That means any class can be accessible.
• Protected – It members cannot be accessed from outside the class, however, they can be accessed in inherited classes.

 Note:

• More details are given in the inheritance concept. Please click the below link to aid for more learning.

Example:

1.  #include<iostream.h>
    #include<conio.h>
    #include<iomanip.h>//output formatting
   class std
   {
   public:
   int sno,m1,m2,m3,m4,m5,tot;
   float avg;
   char name[30];
   void get()//function for value get from user
   {
   cout<<"\n Enter student number : ";
   cin>>sno;
   cout<<"\n Enter student name : ";
   cin>>name;
   cout<<"\n Enter Five subject mark : ";
   cin>>m1>>m2>>m3>>m4>>m5;
   }
   void result()//fuction for calculate total and average
   {
   tot = m1+m2+m3+m4+m5;
   avg =tot/5;
   }
   void display()//function for displaying full details
   {
   cout<<"\n Student details............";
   cout<<"\n Student id is : "<<sno;
   cout<<"\n Student name is : "<<name;
   cout<<"\n Five subject marks : "<<m1<<setw(5)<<m2<<setw(5)<<m3<<setw(5)<<m4<<setw(5)<<m5;
   cout<<"\n Total mark for five subject :"<<tot;
   cout<<"\n Average mark for five subject :"<<avg;
   }
   };
   void main()
   {
   clrscr();
   std s;//object declaration
   //accessing member function using object
   s.get();
   s.result();
   s.display();
   getch();
   }

Output:

Note:

If you need details about iomanip.h header file and setw() function, click the below link to learn.

https://www.whereisstuff.com/2020/09/output-formatting-in-c.html

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