A system that performs real-time garbage collection by dynamically expanding and contracting the heap is provided. This system performs real-time garbage collection in that the system guarantees garbage collection will not take more time than expected. The system dynamically expands and contracts the heap to correspond to the actual memory space used by live objects. This dynamic resizing of the heap has the advantages of expanding when the amount of objects increases and contracting to free memory space for use by other procedures when the amount of objects decreases. Keeping the heap as small as possible frees resources for other processes and increases the locality of reference for the application. This dynamic resizing also ensures that the new memory space will not run out of memory before all of the live objects from the old memory space are copied, even if all of the live objects in the old memory space survive.