dynamic memory allocation in c++
In the dynamic memory allocation the memory is allocated during run time.
The space which is allocated dynamically usually placed in a program segment which is known as heap.
In this, the compiler does not need to know the size in advance.
In C++, dynamic memory allocation means performing memory allocation manually by programmer.
It is allocated on the heap and the heap is the region of a computer memory which is managed by the programmer using pointers to access the memory.
The programmers can dynamically allocate storage space while the program is running but they cannot create a new variable name.
Example:
#include <iostream>
using namespace std;
int main () {
double* pvalue = NULL; // Pointer initialized with null
pvalue = new double; // Request memory for the variable
*pvalue = 29494.99; // Store value at allocated address
cout << "Value of pvalue : " << *pvalue << endl;
delete pvalue; // free up the memory.
return 0;
}
#include <iostream>
#include <string>
using String = std::string;
class Entity
{
private:
String m_Name;
public:
Entity() : m_Name("Unknown") {}
Entity(const String& name) : m_Name(name) {}
const String& GetName() const {
return m_Name;
};
};
int main() {
// new keyword is used to allocate memory on heap
int* b = new int; // new keyword will call the c function malloc which will allocate on heap memory = data and return a ptr to that plaock of memory
int* c = new int[50];
Entity* e1 = new Entity;//new keyword Not allocating only memory but also calling the constructor
Entity* e = new Entity[50];
//usually calling new will call underlined c function malloc
//malloc(50);
Entity* alloc = (Entity*)malloc(sizeof(Entity));//will not call constructor only allocate memory = memory of entity
delete e;//calls a c function free
Entity* e3 = new(c) Entity();//Placement New