Stack vs. Heap: Know the Difference
By Shumaila Saeed || Updated on December 25, 2023
"Stack" is a memory storage region for temporary, LIFO-ordered data, while "Heap" is a memory area for dynamically allocated, disordered data.
Key Differences
In computing, the stack is used for static memory allocation, where sizes and lifetimes of variables are known at compile-time. The heap is used for dynamic memory allocation, allowing allocation and deallocation at runtime.
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Stack operations are LIFO (Last-In-First-Out), meaning the most recently added item is the first to be removed. The heap does not have a specific order for storing and retrieving data, allowing random access.
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The size of the stack is usually determined at the start of the program and can be limited. The heap is typically larger and more flexible, but managing its memory is more complex.
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Stack memory allocation is faster as it involves only moving the stack pointer. Heap allocation is slower due to the need to search for a block of free memory.
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Stack is commonly used for temporary variables and function calls. The heap is used for variables whose size cannot be determined at compile time or that require a lifespan beyond the function's execution.
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Comparison Chart
Memory Allocation
Static, known at compile time
Dynamic, determined at runtime
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Use
Temporary variables, function calls
Long-lived objects, variable size data
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Stack and Heap Definitions
Stack
A memory region for storing temporary variables.
Local variables are stored in the stack during function execution.
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Heap
A non-ordered memory pool for variable-size allocations.
Large data structures are often stored in the heap due to size.
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Nov 11, 2023
Stack
A data structure allowing push and pop operations.
He implemented a stack to manage the undo operations in the app.
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Nov 11, 2023
Heap
A data storage for objects with an unpredictable lifetime.
The heap is used for objects that must exist beyond function scope.
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Nov 11, 2023
Stack
A linear data structure for storing ordered elements.
A stack of integers was used to reverse the numbers.
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Nov 11, 2023
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Heap
A group of things placed or thrown, one on top of the other
A heap of dirty rags lying in the corner.
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Stack
A structure in programming for static memory allocation.
The stack overflow error occurred due to too many recursive calls.
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Heap
Often heaps(Informal) A great deal; a lot
We have heaps of homework tonight.
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Stack
An orderly pile, especially one arranged in layers
A stack of newspapers.
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Stack
A large, usually conical pile of straw or fodder arranged for outdoor storage.
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Stack
(Computers) A section of memory and its associated registers used for temporary storage of information in which the item most recently stored is the first to be retrieved.
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Stack
A group of three rifles supporting each other, butt downward and forming a cone.
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Heap
A pile or mass; a collection of things laid in a body, or thrown together so as to form an elevation.
A heap of earth; a heap of stones
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Heap
(computing) A data structure consisting of trees in which each node is greater than all its children.
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Heap
(computing) Memory that is dynamically allocated.
You should move these structures from the stack to the heap to avoid a potential stack overflow.
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Heap
(colloquial) A dilapidated place or vehicle.
My first car was an old heap.
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Stack
An English measure of coal or cut wood, equal to 108 cubic feet (3.06 cubic meters).
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Heap
(transitive) To pile in a heap.
He heaped the laundry upon the bed and began folding.
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Heap
(transitive) To supply in great quantity.
They heaped praise upon their newest hero.
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Stack
(Games) To prearrange the order of (a deck of cards) so as to increase the chance of winning.
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Heap
Very; representing broken English stereotypically or comically attributed to Native Americans
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Stack
To prearrange or fix unfairly so as to favor a particular outcome
Tried to stack the jury.
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Heap
A crowd; a throng; a multitude or great number of persons.
The wisdom of a heap of learned men.
A heap of vassals and slaves.
He had heaps of friends.
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Stack
To direct (aircraft) to circle at different altitudes while waiting to land.
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Heap
A great number or large quantity of things not placed in a pile; as, a heap of trouble.
A vast heap, both of places of scripture and quotations.
I have noticed a heap of things in my life.
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Heap
A pile or mass; a collection of things laid in a body, or thrown together so as to form an elevation; as, a heap of earth or stones.
Huge heaps of slain around the body rise.
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Heap
To collect in great quantity; to amass; to lay up; to accumulate; - usually with up; as, to heap up treasures.
Though he heap up silver as the dust.
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Stack
A large pile of hay, grain, straw, or the like, larger at the bottom than the top, sometimes covered with thatch.
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Heap
To throw or lay in a heap; to make a heap of; to pile; as, to heap stones; - often with up; as, to heap up earth; or with on; as, to heap on wood or coal.
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Stack
A pile of similar objects, each directly on top of the last.
Please bring me a chair from that stack in the corner.
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Heap
To form or round into a heap, as in measuring; to fill (a measure) more than even full.
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Heap
(often followed by `of') a large number or amount or extent;
A batch of letters
A deal of trouble
A lot of money
He made a mint on the stock market
It must have cost plenty
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Heap
A car that is old and unreliable;
The fenders had fallen off that old bus
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Heap
Bestow in large quantities;
He heaped him with work
She heaped scorn upon him
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Heap
Arrange in stacks;
Heap firewood around the fireplace
Stack your books up on the shelves
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Stack
(programming) A linear data structure in which items inserted are removed in reverse order (the last item inserted is the first one to be removed).
History stack
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Stack
A stack data structure stored in main memory that is manipulated during machine language procedure call related instructions.
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Heap
A memory region for dynamic allocation of variables.
Objects are dynamically allocated in the heap in Java.
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Stack
An implementation of a protocol suite (set of protocols forming a layered architecture).
A TCP/IP stack is a library or set of libraries or of OS drivers that take care of networking.
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Heap
An area in memory where the size is not fixed at compile time.
He used the heap to allocate memory for the variable-size array.
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Stack
A combination of interdependent, yet individually replaceable, software components or technologies used together on a system.
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Heap
A structure allowing allocation and deallocation at runtime.
Memory leaks in the heap can occur if not properly managed.
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Stack
(math) A generalization of schemes in algebraic geometry and of sheaves.
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Stack
(geology) A coastal landform, consisting of a large vertical column of rock in the sea.
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Stack
(library) Compactly spaced bookshelves used to house large collections of books.
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Stack
(figuratively) A large amount of an object.
They paid him a stack of money to keep quiet.
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Stack
(bodybuilding) A blend of various dietary supplements or anabolic steroids with supposed synergistic benefits.
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Stack
(aviation) A holding pattern, with aircraft circling one above the other as they wait to land.
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Stack
(video games) The quantity of a given item which fills up an inventory slot or bag.
I've got 107 Golden Branches, but the stack size is 20 so they're taking up 6 spaces in my inventory.
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Stack
(transitive) To arrange in a stack, or to add to an existing stack.
Please stack those chairs in the corner.
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Stack
To arrange the cards in a deck in a particular manner.
This is the third hand in a row where you've drawn four of a kind. Someone is stacking the deck!
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Stack
To take all the money another player currently has on the table.
I won Jill's last $100 this hand; I stacked her!
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Stack
(transitive) To deliberately distort the composition of (an assembly, committee, etc.).
The Government was accused of stacking the parliamentary committee.
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Stack
To crash; to fall.
Jim couldn′t make it today as he stacked his car on the weekend.
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Stack
(gaming) To operate cumulatively.
A magical widget will double your mojo. And yes, they do stack: if you manage to get two magical widgets, your mojo will be quadrupled. With three, it will be octupled, and so forth.
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Stack
To collect precious metal in the form of various small objects such as coins and bars.
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Stack
A large and to some degree orderly pile of hay, grain, straw, or the like, usually of a nearly conical form, but sometimes rectangular or oblong, contracted at the top to a point or ridge, and sometimes covered with thatch.
But corn was housed, and beans were in the stack.
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Stack
An orderly pile of any type of object, indefinite in quantity; - used especially of piles of wood. A stack is usually more orderly than a pile
Against every pillar was a stack of billets above a man's height.
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Stack
A section of memory in a computer used for temporary storage of data, in which the last datum stored is the first retrieved.
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Stack
The section of a library containing shelves which hold books less frequently requested.
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Stack
To lay in a conical or other pile; to make into a large pile; as, to stack hay, cornstalks, or grain; to stack or place wood.
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Stack
To place in a vertical arrangement so that each item in a pile is resting on top of another item in the pile, except for the bottom item; as, to stack the papers neatly on the desk; to stack the bricks.
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Stack
To select or arrange dishonestly so as to achieve an unfair advantage; as, to stack a deck of cards; to stack a jury with persons prejudiced against the defendant.
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Stack
(often followed by `of') a large number or amount or extent;
A batch of letters
A deal of trouble
A lot of money
He made a mint on the stock market
It must have cost plenty
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Stack
A list in which the next item to be removed is the item most recently stored (LIFO)
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Stack
A large tall chimney through which combustion gases and smoke can be evacuated
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Stack
A storage device that handles data so that the next item to be retrieved is the item most recently stored (LIFO)
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Stack
Arrange in stacks;
Heap firewood around the fireplace
Stack your books up on the shelves
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Stack
Arrange the order of so as to increase one's winning chances;
Stack the deck of cards
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Stack
A collection of elements organized by LIFO principle.
The call stack keeps track of function calls in a program.
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Repeatedly Asked Queries
What is heap memory used for?
Heap memory is used for allocating memory dynamically at runtime.
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Is stack memory faster than heap?
Yes, stack memory allocation is typically faster than heap allocation.
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What is a stack in computer memory?
A stack is a region in memory for storing temporary data in a LIFO order.
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How does stack memory work?
Stack memory stores variables as the program executes, using a LIFO order.
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Can heap memory size change during execution?
Yes, heap memory size can change dynamically during program execution.
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How is memory managed in the heap?
Memory in the heap is managed through allocation and deallocation, often manually or via garbage collection.
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Why is stack memory limited?
Stack memory is limited to ensure efficient management and to prevent overuse of memory resources.
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What is a memory leak in the heap?
A memory leak in the heap occurs when allocated memory is not properly deallocated, leading to wasted memory.
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How does garbage collection work in the heap?
Garbage collection automatically frees up memory in the heap by removing objects that are no longer in use.
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What is a heap in computer memory?
A heap is a memory area for dynamically allocated, unordered data.
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Is stack memory secure?
Stack memory is generally more secure due to its temporary nature and limited access.
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What causes a stack overflow?
A stack overflow occurs when there’s too much data for the stack to handle, often due to deep or infinite recursion.
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Can objects be stored in the stack?
Yes, small objects or primitives are often stored in the stack, but larger objects typically use heap memory.
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Can heap memory be accessed globally?
Heap memory can be accessed globally as it’s not restricted to specific function scope.
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What is the main disadvantage of using heap memory?
The main disadvantage of using heap memory is its slower speed and the complexity of memory management.
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What happens when the heap is full?
When the heap is full, it can lead to a memory allocation error or a program crash.
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Can the stack size be adjusted?
The stack size can sometimes be adjusted, but it's fixed at the start of the program execution.
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Are local variables stored in the stack?
Yes, local variables are typically stored in the stack.
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Do threads have separate stacks?
Yes, each thread in a program generally has its own stack.
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What is dynamic memory allocation in the heap?
Dynamic memory allocation in the heap refers to allocating and deallocating memory as needed during runtime.
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About Author
Written by
Shumaila SaeedShumaila Saeed, an expert content creator with 6 years of experience, specializes in distilling complex topics into easily digestible comparisons, shining a light on the nuances that both inform and educate readers with clarity and accuracy.
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