C++ Pointers malloc() vs new

Syntax of malloc() in C++

ptr = (cast-type*)malloc(byte-size);

Syntax of new operator in C++

ptr = new data-type;

Example of malloc() in C++

#include <iostream>
#include <cstdlib>
using namespace std;
int main() {
    int* ptr;
    int n = 5;
    ptr = (int*)malloc(n * sizeof(int));
    if (ptr == NULL) {
        cout<<"Memory not allocated"<<endl;
        exit(0);
    } else {
        cout<<"Memory allocated successfully"<<endl;
        for (int i = 0; i < n; i++) {
            ptr[i] = i + 1;
        }
        cout<<"The values of the array are: ";
        for (int i = 0; i < n; i++) {
            cout<<ptr[i]<<" ";
        }
        free(ptr);
    }
    return 0;
}

Output of malloc() in C++

Memory allocated successfully
The values of the array are: 1 2 3 4 5

Explanation of malloc() in C++

malloc is used to allocate a block of memory of the specified size and returns a pointer of type void, which can be cast to a pointer of any form.

Use of malloc() in C++

1. It is fast and efficient for allocating large blocks of memory.
2. It is useful when the size of memory to be allocated is not known until run time.

Important Points of malloc() in C++

1. It does not call the class constructor.
2. It is a function.
3. It returns a void pointer.

Example of new operator in C++

#include <iostream>
using namespace std;
int main() {
    int* ptr;
    int n = 5;
    ptr = new int[n];
    if (ptr == NULL) {
        cout<<"Memory not allocated"<<endl;
    } else {
        cout<<"Memory allocated successfully"<<endl;
        for (int i = 0; i < n; i++) {
            ptr[i] = i + 1;
        }
        cout<<"The values of the array are: ";
        for (int i = 0; i < n; i++) {
            cout<<ptr[i]<<" ";
        }
        delete [] ptr;
    }
    return 0;
}

Output of new operator in C++

Memory allocated successfully
The values of the array are: 1 2 3 4 5

Explanation of new operator in C++

The new operator is used to allocate memory dynamically. It returns a pointer to the beginning of the memory block.

Use of new operator in C++

1. It is useful for creating objects of classes.
2. It can allocate memory for multiple objects of the same class.

Important Points of new operator in C++

1. It calls the class constructor.
2. It is an operator.
3. It returns a pointer of the same type as the object being created.

Summary

Both malloc and new can be used to allocate memory dynamically in C++. However, new is usually preferred as it calls the class constructor and returns a pointer of the same type as the object being created. malloc returns a void pointer and does not call the class constructor.