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An area of memory used for dynamic memory allocation where blocks of memory are allocated and freed in an arbitrary order and the pattern of allocation and size of blocks is not known until run time. Typically, a program has one heap which it may use for several different purposes.

Heap is required by languages in which functions can return arbitrary data structures or functions with free variables (see closure). In C functions malloc and free provide access to the heap.

Contrast stack. See also dangling pointer.


A data structure with its elements partially ordered (sorted) such that finding either the minimum or the maximum (but not both) of the elements is computationally inexpensive (independent of the number of elements), while both adding a new item and finding each subsequent smallest/largest element can be done in O(log n) time, where n is the number of elements.

Formally, a heap is a binary tree with a key in each node, such that all the leaves of the tree are on two adjacent levels; all leaves on the lowest level occur to the left and all levels, except possibly the lowest, are filled; and the key in the root is at least as large as the keys in its children (if any), and the left and right subtrees (if they exist) are again heaps.

Note that the last condition assumes that the goal is finding the minimum quickly.

Heaps are often implemented as one-dimensional arrays. Still assuming that the goal is finding the minimum quickly the invariant is

heap[i] <= heap[2*i] and heap[i] <= heap[2*i+1] for all i,

where heap[i] denotes the i-th element, heap[1] being the first. Heaps can be used to implement priority queues or in sort algorithms.


In programming, it refers to a common pool of memory that is available to the program. The management of the heap is either done by the applications themselves, allocating and deallocating memory as required, or by the operating system or other system program.
References in periodicals archive ?
They have been faithful to and supportive of each other through financial disaster, personal tragedy, countless family problems, disease and disability, and the hatred and violence society heaps upon them.
The residents of these areas told no sweeper is appointed by the respective department, therefore, they are forced to live a life of pariahs amid the heaps upon heaps of filth.
To top off the injury that the city heaps upon the Valley, the most disgusting insult of all will be the 200 to 400 or more trucks a day that will haul sewage from La Canada Flintridge to Malibu, and everywhere in between, to the Valley, thus transforming the Sepulveda Basin into a huge cesspool.