Access to member variables from objects

🔷 What Are Member Variables?

Member variables (also called data members) are variables declared inside a class. These variables hold the data for each object.

Each object of a class gets its own copy of the member variables.

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🔷 Accessing Member Variables from Objects

To access member variables, we use the dot operator (.) with the object name.

✅ Syntax:

objectName.variableName;

This allows you to read or assign values to the variable.

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🔷 Example: Accessing Member Variables

#include <iostream>
using namespace std;

class Student {
public:
    int rollNo;
    string name;
};

int main() {
    Student s1;  // Object of class Student

    // Accessing member variables using object
    s1.rollNo = 101;
    s1.name = "Alice";

    // Displaying values
    cout << "Roll Number: " << s1.rollNo << endl;
    cout << "Name: " << s1.name << endl;

    return 0;
}

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🔷 Explanation:

• s1 is an object of class Student.
• s1.rollNo and s1.name are used to access the public member variables.
• You can assign values or print values using this syntax.

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🔒 Private Member Variables and Access

If member variables are private, they cannot be accessed directly using the object.

Example:

class Student {
private:
    int rollNo;

public:
    void setRollNo(int r) {
        rollNo = r;
    }

    int getRollNo() {
        return rollNo;
    }
};

int main() {
    Student s1;
    // s1.rollNo = 101; // ❌ Error: 'rollNo' is private
    s1.setRollNo(101);  // ✅ Allowed via public function
    cout << "Roll No: " << s1.getRollNo() << endl;
}

🔸 This is a principle of encapsulation: keeping data safe and accessible only through controlled functions (getters/setters).

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🔷 Table: Access Based on Specifier

Access Specifier	Access from Object	Access in Class Functions
public	✅ Yes	✅ Yes
private	❌ No	✅ Yes
protected	❌ No	✅ Yes (in derived classes)

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🔷 Real-Life Analogy

Think of a bank account class:

• balance is a private member variable.
• You can’t take money directly (not safe!).
• You use deposit() and withdraw() functions to access it safely — just like you use get and set methods in C++.

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🔷 Summary

• Use the dot operator to access member variables: cppCopyEditobjectName.variableName;
• Public variables can be accessed directly.
• Private variables need to be accessed through member functions.
• This ensures security and encapsulation in OOP.