Access specifiers in C++ - Step-by-Step Execution

Concept Flow - Access specifiers

Start Class Definition

↓

Declare Members

↓

Apply Access Specifiers

↓

public

↓

Accessible

↓

Use Members in Code

↓

Check Access Rules

↓

Allow or Deny Access

↓

End

This flow shows how class members are declared with access specifiers and how access is checked during usage.

Execution Sample

C++

class MyClass {
public:
  int x;
private:
  int y;
};

MyClass obj;
obj.x = 5; // allowed
obj.y = 10; // error

This code defines a class with public and private members and shows which members can be accessed.

Execution Table

Step	Code Line	Action	Access Check	Result
1	class MyClass {	Start class definition	N/A	Class created
2	public:	Set access to public	N/A	Members below are public
3	int x;	Declare member x	Public	Accessible anywhere
4	private:	Set access to private	N/A	Members below are private
5	int y;	Declare member y	Private	Accessible only inside class
6	};	End class definition	N/A	Class finalized
7	MyClass obj;	Create object obj	N/A	Object created
8	obj.x = 5;	Access public member x	Allowed	Value 5 assigned
9	obj.y = 10;	Access private member y	Denied	Compilation error

💡 Access to private member y is denied, stopping compilation.

Variable Tracker

Variable	Start	After Step 8	After Step 9
obj.x	undefined	5	5
obj.y	undefined	undefined	undefined (access denied)

Key Moments - 2 Insights

Why can we assign to obj.x but not to obj.y?

obj.x is declared public (see step 3 and 8), so it is accessible outside the class. obj.y is private (step 5), so access outside the class is denied (step 9).

What happens if we try to access a private member from outside the class?

The compiler stops the program with an error (step 9), because private members are only accessible inside the class.

Visual Quiz - 3 Questions

Look at the execution table, what is the access level of member x?

A private

B public

C protected

D default

💡 Hint

See step 3 and 8 in the execution_table where x is declared public and accessed successfully.

At which step does the program stop due to access violation?

A Step 7

B Step 8

C Step 9

D Step 6

💡 Hint

Check step 9 in the execution_table where accessing private member y is denied.

If member y was declared public instead of private, what would happen at step 9?

A Value 10 assigned successfully

B Runtime error occurs

C Compilation error remains

D Member y is inaccessible

💡 Hint

Refer to step 8 where public member x is assigned successfully; public y would behave the same.

Concept Snapshot

Access specifiers control who can use class members.
public: accessible anywhere.
private: accessible only inside the class.
protected: accessible inside class and subclasses.
Use them to protect data and control access.

Full Transcript

This visual trace shows how access specifiers in C++ control access to class members. The class MyClass has two members: x declared public and y declared private. When creating an object obj, accessing obj.x is allowed and assigns the value 5. However, accessing obj.y causes a compilation error because y is private and cannot be accessed outside the class. The variable tracker shows obj.x changes from undefined to 5, while obj.y remains inaccessible. Key moments clarify why public members are accessible and private members are not. The quiz tests understanding of access levels and error steps. Remember, access specifiers help protect data and define who can use class parts.