Question about Classes and Structure

Hi,

I am having problem with Classes, I have made a small program of Classes which is :

Code:

---


main()


Class Student ------------------(1)

{

public :
Student(): //constructor

defined some functions here.

private:

int age;
int grade;
char name;
char address;


};




{

Student mystudent; ------------(2)

/* manipulate the data members

{
mystudent.age;
mystudent.address;
mystudent.name;
mystudent.grade;

}

---

------------------------------------------

I have made this small program of Class, I have also defined the data members of the data but when I compile the program, it gives me error messege.Am I geting this error because the class is defined private?
How can I make the data members in (2) to access the Class in (1)?

I hope my questions are clear

The entire purpose of declaring members private (preceding them by the private keyword and a colon in the class definition, as you have done) is to make them inaccessible to arbitrary code - hence the error messages.

The only code that is allowed to access a private member of class Student is a member function of class Student or friends. If a function is declared as a friend, then that function can access private members. If another class is declared as a friend, then all member functions of that class can access private members.

Also, the keyword is class not Class. Capitalisation is important.

There's a lot wrong with your code. Take a look at this. Lots of the bugs are fixed, and I inserted some comments about various parts of the code...

Code:

---

#include <iostream>

class Student {
public:
  Student(){}
 
private:
  int age;
  int grade; // should this be char?
  char name;
  // Should probably be char name[LENGTH] where LENGTH
  // is the length of the string you want defined, or seeing how
  // you're using C++ you might as well use std::string name
  //after #including <string>
  char address; // Same comments as per name
};

// Main returns int
int main() {
  Student myStudent;
  // Well, as it is defined this is all you can do with this :-) You need to add some functionality
 

  return 0;
}

---

However, if all you want is to store age, grade, name and address you might consider using a struct instead of a class. As it is your class doesn't do anything. You'll need to define and implement functionality, like getters/setters if you want.

Hi

So do we have to define the class outside of the main() function?

Is it case sensitive, do we have to use class instead of Class?

If you define the class inside a function then it is only available for use inside the function you've defined it in. By making the definition global, all functions that need to make use of the class can do so. The individual instances of said class should be kept as local as possible but the definition should be global.

The language is case sensitive, it must be class (all lowercase).

Well,

I want to do more with these data,thats why I wanted to use "Class" instead of "Struct".

I want to have a small database sort of thing so that any user who wants to access the info of a perticular student can do it.


Student info:


Name:

Address:

Roll No:

Class:

In the case of class, these info is private but I wanted to know that how can we manipulate these data members in Classes?

I have already defined functions "getter" and "setter" in the public of the class.



I hope I am clear

Hi,

I have got some other questions, how can I use constructor to initialize these data members inside the class?

I have simply defined the constructor as "Student()".

It might be preferable to have a constructor so you can initialize all the members in one go.
Also replace your "char" with "std::string". A "char" is not a string.

Hi,

I also wanted to know for what do we use "getter" and "setter" function?

Thanks

To protect yourself from code changes. If the means of getting a value changes in the future (say that you suddenly start storing your data in a database), then you only have to change the getter function. The rest of your code that uses the getter function will keep on working like before.
Otherwise you have to change every place that gets that value.