FAQ heaps

[face_master]

I do not understand what heaps are. what are used for and why they are used. After searching everywhere, all that I could find out is that a heap has something to do with memory (eg. 0x1256...or some garbage like that).

Thanks
-Chris

[Dang]

The heap is reserved for dynamic memory allocation needs of the program. It is an area apart from the program code and the stack. Typical C programs use the functions malloc and free to allocate and deallocate heap memory. C++ uses the new and delete operator. The new operatroe allocates the memory then calls the constructor to initialize it. The delete operator does all the necessary (hopefully) cleanup then the memory is made availible (deallocated) for reuse on the heap.

To allocate an array of bytes on the stack

The array is automatically deleted and its memory reclaimed when the array variable exits its scope.
{
const int BUFF_SIZE = 128;

// Allocate on the frame
char myCharArray[BUFF_SIZE];
int myIntArray[BUFF_SIZE];
// Reclaimed when exiting scope
}

To allocate an array of bytes (or any primitive data type) on the heap

Use the new operator with the array syntax shown in this example:
const int BUFF_SIZE = 128;

// Allocate on the heap
char* myCharArray = new char[BUFF_SIZE];
int* myIntArray = new int[BUFF_SIZE];

//Reclaimed with delete
delete [] myCharArray;
delete [] myIntArray;

[zen]

Or if you after a more general definition of a heap data structure then look here