Dynamic Memory

Overview

Local variables are stored on the Stack (small, automatic). Dynamic memory is allocated on the Heap (huge, manual) using `new` and must be manually freed using `delete`.

Syntax

cpp

// Allocate an integer on the Heap
int* ptr = new int;
*ptr = 42;

// Allocate and initialize
int* ptr2 = new int(100);

// FREE the memory to prevent leaks
delete ptr;
delete ptr2;

// Good practice: nullify the pointer
ptr = nullptr;

Common Pitfalls

Forgetting to `delete`, leading to memory leaks that eventually crash the program (OOM - Out of Memory).

Interview Tips

A Memory Leak occurs when you lose all pointers to dynamically allocated memory without calling `delete`.
A Dangling Pointer occurs when you call `delete ptr`, but you try to use `ptr` again later. Always set `ptr = nullptr` after deleting.

Real-World Example

Allocating a large object on the heap to save stack space.

example

cpp

#include <iostream>
using namespace std;

struct MassiveData {
    long long data[10000];
};

int main() {
    // Allocating on heap prevents Stack Overflow
    MassiveData* md = new MassiveData();
    md->data[0] = 500;
    
    cout << "Value: " << md->data[0] << endl;
    
    delete md; // Crucial!
    return 0;
}

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