Basic Pointers in C++

Basic Pointer Program in C++.

BeginnerMemory Management ProgramsExample 1 of 11

basic-pointers.cpp

1#include <iostream>
2using namespace std;
3
4int main() {
5    int num = 10;
6    
7    // Declare a pointer
8    int* ptr;
9    
10    // Store address of num in pointer
11    ptr = &num;
12    
13    cout << "Value of num: " << num << endl;
14    cout << "Address of num: " << &num << endl;
15    cout << "Value of ptr (address stored): " << ptr << endl;
16    cout << "Address of ptr: " << &ptr << endl;
17    cout << "Value pointed by ptr: " << *ptr << endl;
18    
19    // Modify value using pointer
20    *ptr = 20;
21    cout << "\nAfter modifying through pointer:" << endl;
22    cout << "Value of num: " << num << endl;
23    cout << "Value pointed by ptr: " << *ptr << endl;
24    
25    return 0;
26}

Output

Value of num: 10
Address of num: 0x7fff5fbff6ac
Value of ptr (address stored): 0x7fff5fbff6ac
Address of ptr: 0x7fff5fbff6a0
Value pointed by ptr: 10

After modifying through pointer:
Value of num: 20
Value pointed by ptr: 20

What's going on

The program demonstrates basic pointer operations:

Declaring a pointer variable

Getting address of a variable using & operator

Storing address in pointer

Accessing value through pointer using * operator (dereferencing)

Pointers allow you to work with memory addresses directly.

Header File Used

This header provides:

cout for displaying output

cin for taking input from the user

1#include <iostream>

Understanding Pointers

Pointer Concept

Variable that stores memory address

Points to location of another variable

Enables indirect access to data

Fundamental for dynamic memory

Memory Address

Every variable has a memory address

Address is where data is stored

Pointer stores this address

Can access data through address

Declaring Pointers

Syntax

dataType* pointerName;

Example

int* ptr; // Pointer to integer

How it works

* indicates pointer type

ptr can store address of int variable

Initially contains garbage (uninitialized)

Address Operator (&)

Getting Address

int num = 10;

int* ptr = &num; // & gets address of num

How it works

& operator returns memory address

Address stored in pointer variable

Example: &num returns address like 0x7fff5fbff6ac

Dereference Operator (*)

Accessing Value

int value = *ptr; // * accesses value at address

How it works

* operator dereferences pointer

Accesses value at stored address

Example: *ptr returns value 10 (from num)

Pointer Operations

Declaration and Initialization

int num = 10;

int* ptr = &num;

Accessing Value

1cout << *ptr;  // Prints 10

Modifying Through Pointer

*ptr = 20; // Changes num to 20

Getting Address

1cout << ptr;  // Prints address
2cout << &num;  // Same address

When to Use Pointers

Best For

Dynamic memory allocation

Passing parameters by reference

Arrays and strings

Data structures (linked lists, trees)

Function parameters (modify original)

Example Scenarios

Allocating memory at runtime

Passing large objects efficiently

Implementing data structures

Working with arrays

Important Considerations

Initialization

Always initialize pointers

Uninitialized pointers are dangerous

Initialize to nullptr if not pointing anywhere

Null Pointers

nullptr: doesn't point to anything

Always check before dereferencing

Prevents crashes

Dereferencing

Only dereference valid pointers

Check for null before use

Undefined behavior if invalid

return 0;

This ends the program successfully.

NextPointer Arithmetic