Take the 2-minute tour ×

A heap is a tree data structure where higher levels of the tree always contain greater (or lesser, if it's set up that way) values than lower levels. "The" heap is a bunch of free RAM that a program has available for dynamic allocation. They're both called "heap," but what does the one have to do with the other?

share|improve this question

9 Answers 9

up vote 10 down vote accepted

Nothing much, to be honest. I would imagine that the word heap was simply taken with it's everday (non-technical) usage and applied to these two concepts individually as reasonably good analogies.

In the first case (tree data structure meaning), the description heap is most appropiate because "greater" objects are placed higher up in the tree (where "greater" is determined by an arbitrary key function) - i.e. there's a sort of piling of smaller objects on top of larger ones (or larger on top, depending how you think of it). This is just how I'd interpret it; whoever first applied the name heap to this data-structure thought it was an appropiate name in his mind, and it's just stuck.

In the second case (chunks of RAM), the name of heap is maybe a bit more evident. "Heap" is just "a large collection of things in a highly arbitrary order" here, which would seem to apply just as well in common usage as it does to dynamically allocated chunks of memory.

In any case, I wouldn't worry about the abstract metaphorical similarities you can draw between the two ideas. Treat them completely seperately and you won't go wrong in any situation.

Edit: It seems the tree-based data structure may have taken its name from the heap of abstract algebra, as is reasonably common within computer science. However, I wouldn't want to confirm or deny this...

share|improve this answer

See this very site for an exploration of the origin of the name "heap" for the free store of memory.

share|improve this answer

They both have the same name, that's about it.
There 'the heap' is never arranged as an actual heap data structure.

share|improve this answer

The heap (datastructure) is called like that because if you draw it it looks like a heap. The heap (memory) is called a heap because it is somehow organized but not fully. You accumulate data on a heap but you might have holes in it and irregularities. It's as if you'd put papers on a heap. Sometimes you remove one from the bottom. This has a form of a heap, i.e. somehow organized but not fully.

share|improve this answer

The only relationship between the two is the name "heap."

share|improve this answer

Nothing. No relation.

share|improve this answer

They...have the same name! That's it.

share|improve this answer

Definition from answers.com

Heap: A group of things placed or thrown, one on top of the other: a heap of dirty rags lying in the corner.

It's just basic naming due to the conceptual image of throwing things in an unordered fashion. As other posters point out, the heap is not organized as a heap data structure. That depends on the memory allocation routines in your system library (eg. check how malloc works)

share|improve this answer

To futher complicate the question: on some systems (e.g. Microsoft Windows), there are multiple "heaps" in the memory allocation sense. "The" heap is merely the default heap. But if you call HeapAlloc(), you can choose from which memory allocation you want a sub-allocation.

share|improve this answer

Your Answer


