   Implementation details of new and delete
  When we do delete[], how does compiler finds out how many elements to delete?I have heard a bit about Arena Header...can anyone give some details about it or the details of whatever relevent.   
  Usually it allocates 4 bytes more than the room for just the elements and then stores the number of elements at the front of the allocated memory. Then when it returns it uses the address four bytes after the location of the element count.   ;In any of at least two different ways depending on your compiler.