📌 Pointer Basics

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Creating a Variable

int number = 99;

Variable "number" stores the value:

number = 99

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Creating a Pointer

int* ptr = &number;

Meaning

• ptr stores the address of number
• &number means the memory address of number

Illustration

ptr
 ↓
number
 ↓
99

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Dereference ("*")

*ptr

Meaning: "Get the value from the address pointed to by ptr."

Result: 99

Summary

Expression	Result
ptr	Address of number
*ptr	Value of number (99)

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🔗 Pointer to Pointer

Creating a Double Pointer

int number = 99;
int* ptr = &number;
int** ptr2 = &ptr;

Illustration

ptr2
 ↓
ptr
 ↓
number
 ↓
99

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Understanding Pointer Layers

Expression	Result
ptr	Address of number
*ptr	99
ptr2	Address of ptr
*ptr2	ptr
**ptr2	99

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✏️ Changing Value Through Pointer

int number = 1;
int* ptr = &number;
*ptr = 10;

Result: number = 10

Why?

Because:

ptr
 ↓
number

So changing through *ptr directly changes the value of number.

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🧮 Important Example

int number = 1;
int* ptr = &number;
int** ptr2 = &ptr;

*ptr = 10;
**ptr2 = **ptr2 + *ptr;

Step by Step

Step	Action	Result
1	number = 1	number = 1
2	*ptr = 10	number = 10
3	**ptr2 = **ptr2 + *ptr	10 = 10 + 10
4	**ptr2 = 20	number = 20

Final Output: 20

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💡 How to Think When Dealing with Pointers

Don't memorize. Follow the arrows:

ptr2
 ↓
ptr
 ↓
number
 ↓
99

Each * means: "Follow one more arrow."

Example

Expression	Meaning
*ptr2	Follow one arrow → ptr
**ptr2	Follow two arrows → 99

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📝 Complete Code Example

#include <iostream>
using namespace std;

int main() {
    // Create a variable
    int number = 99;
    
    // Create a pointer to number
    int* ptr = &number;
    cout << "number = " << number << endl;           // 99
    cout << "ptr (address) = " << ptr << endl;       // Memory address
    cout << "*ptr (value) = " << *ptr << endl;       // 99
    
    // Create a pointer to pointer
    int** ptr2 = &ptr;
    cout << "\nptr2 (address of ptr) = " << ptr2 << endl;  // Address of ptr
    cout << "*ptr2 (ptr itself) = " << *ptr2 << endl;      // Same as ptr
    cout << "**ptr2 (value) = " << **ptr2 << endl;         // 99
    
    // Change value through pointer
    *ptr = 50;
    cout << "\nAfter *ptr = 50:" << endl;
    cout << "number = " << number << endl;           // 50
    cout << "*ptr = " << *ptr << endl;               // 50
    cout << "**ptr2 = " << **ptr2 << endl;           // 50
    
    return 0;
}

Expected Output

number = 99
ptr (address) = 0x7ffc8b1c4a4c
*ptr (value) = 99

ptr2 (address of ptr) = 0x7ffc8b1c4a50
*ptr2 (ptr itself) = 0x7ffc8b1c4a4c
**ptr2 (value) = 99

After *ptr = 50:
number = 50
*ptr = 50
**ptr2 = 50

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📊 Summary

Pointers are not monsters.

Expression	Meaning
ptr	Address
*ptr	Value at the address
ptr2	Address of ptr
*ptr2	ptr
**ptr2	Value at the address pointed to by ptr

Main Principle

"Follow the arrows one by one."

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🎯 Visual Reference

Single Pointer

Memory Address    Variable Name    Value
0x1000           →    ptr         →  0x2000
0x2000           →    number      →  99

Reading *ptr:

1. Go to ptr → get 0x2000
2. Go to 0x2000 → get 99

Double Pointer

Memory Address    Variable Name    Value
0x3000           →    ptr2        →  0x1000
0x1000           →    ptr         →  0x2000
0x2000           →    number      →  99

Reading **ptr2:

1. Go to ptr2 → get 0x1000
2. Go to 0x1000 → get 0x2000
3. Go to 0x2000 → get 99

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✅ Learning Status

Topic	Status
Basic Pointers (*)	✅ Done
Pointer to Pointer (**)	✅ Done
Pointer to Pointer to Pointer (***)	🚀 Next

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💪 Practice Exercises

Exercise 1: Basic Pointer

int x = 50;
int* p = &x;
cout << *p;  // What does this print?

Answer: 50

Exercise 2: Change Value

int x = 10;
int* p = &x;
*p = 20;
cout << x;  // What does this print?

Answer: 20

Exercise 3: Double Pointer

int x = 100;
int* p = &x;
int** pp = &p;
cout << **pp;  // What does this print?

Answer: 100

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Last Updated: June 2026