malloc vs new in C++

malloc vs new in C++

In this chapter of C++ interview questions, we will learn about:

  • malloc in c++ and malloc syntax
  • new in c++ and new syntax
  • malloc vs new in c++

To provide flexibility to the programmers, Dynamic Memory Allocation(DMA) is an important concept.


It allocates memory in the Heap. Its application is wide like you can use for variable-length array as well for Data Structures like a linked list, tree.


C uses calloc() and malloc() for DMA.

C++ also has this along with new & delete operators for allocating and free memory.


Unused memory needs to be de-allocated otherwise there will be a Memory Leak issue

Lets learn a bit more about malloc and new in c++ along with their syntax.

Malloc() in C++

malloc() in C++ is a library function used for allocating memory dynamically.


Malloc() in C++:

  • allocates a block of memory, but doesn't initialize.
  • and returns a pointer of void.

malloc syntax

ptr =(datatype*) malloc(size);

New in C++

New in C++ is an operator used to request for memory allocation.


If memory is free,

  • new operator initializes memory and
  • returns the address of new allocated space.

new syntax

pointer_var = new datatype;

Difference between malloc and new

Lets see the difference between malloc and new in c++.

Serial No.




malloc() doesn’t call constructor

new calls constructor


malloc() is a function

new is a operator


malloc() returns void pointer

new returns same data type


On failure condition it returns NULL

It returns bad_allocation


cpp interview questions

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Subhajit Guha Thakurta
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