Question

what is difference between new and malloc ??

Answer 1

The main difference between new and malloc is that new invokes the object's constructor and the corresponding call to delete invokes the object's destructor.
Also 'new' is only available in C++. malloc() is available in both C and C++.
There are other differences:
1. new is type-safe, malloc returns objects of type void*
2. new throws an exception on error, malloc returns NULL and sets errno
3. new is an operator and can be overloaded, malloc is a function and cannot be overloaded
4. new[], which allocates arrays, is more intuitive and type-safe than malloc
5. malloc-derived allocations can be resized via realloc, new-derived allocations cannot be resized
6. malloc can allocate an N-byte chunk of memory, new must be asked to allocate an array of, say, char types

Answer 2

new is the C++ implementation of the memory allocation while malloc is the way of allocation in C.

• malloc allocates uninitialized memory. The allocated memory has to be released with free. (calloc is like malloc but initializes the allocated memory with a constant (0))
• new initializes the allocated memory by calling the constructor (if it's an object). Memory allocated with new should be released with delete (which in turn calls the destructor). It does not need you to manually specify the size you need and cast it to the appropriate type. Thus, it's more modern and less prone to errors.