Aman Goel | 07 Dec, 2022

Stack vs Heap: What's the Difference?

Programming is a world unto its own as there are plenty of facets and variables to the job. A programmer spends long hours huddled in front of a computer typing out code for web pages, software, hardware, and other uses. While numerous tools are available to programmers, stack and heap — memory allocation-based — are the first two critical tools.

You may ask, "What are stack and heap, and what are major differences between the two?" Also, when it comes to stack vs. heap, which one is better to use?

In this article, we will highlight the differences between the two and answer some of your questions.

What is a Stack?

A stack is a structure that represents a sequence of objects or elements that are available in a linear data structure. What does that mean? It simply means you can add or remove elements in a linear order. This way, a portion of memory that keeps variables created can function temporarily.

You can think of a stack like a stack of plates, as shown in the visualization above.

With a stack, declaration, storage, and initialization of variables happen during runtime. The stack’s process is similar to Apple’s old disk RAM of the late 1990s as stack memory auto-erases the data within it once the task has been completed. Hence the data structure within a stack can be easily accessible like Flash Memory or NAND.

One drawback about stacks is that variables can’t be resized, and the memory is allocated in one block. There are also OS-based size limits, and these sizes can’t be adjusted as they are fixed.

Pros of Stack

  • Stack memory can be a big help when compiling code with many benefits available to the programmer.
  • You have complete control over how the memory is allocated and deallocated, which is important to the process.
  • You can manage data in a LIFO (Last In First Out) method, which simply isn’t possible with heap.
  •  Your objects are cleaned up automatically under stack memory, and your variables can’t be resized.
  • Your local variables are stored in a stack under a "called function" and immediately terminated upon return.

Cons of Stack

There are some downsides to using a stack when programming code.

  • The memory size is limited, so if you need a large portion of memory, the stack will not fit the bill.
  • You can run the risk of stack overflow by putting too many objects in the stack while compiling code.
  • You lose the ability for random access while using the stack, and you can overwrite variable storage, which can affect the behavior of the program or function.

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What is a Heap?

Heap memory, in comparison, can store global variables (stack can only store local variables), and there are fewer restrictions on what you can do with heap memory.

Heap stores data on a hierarchical system, and thus the access is a bit slower than stack memory. Heap memory can get clogged up over time with fragmentation as old platter hard drives did back in the day.

One bright spot about heap is that there are no limits on memory sizes, and variables can be resized if you need to.

Due to the storing similarities of old platter hard drives, heap memory works similarly with memory being stored randomly. This is why access speed is slower, as the data needs to be retrieved from many random spots within the chip.

Pros of Heap

  • There are big pluses on the heap, possibly the biggest one being that there are no limits when it comes to memory size.
  • Do you need a huge allocation of memory? Heap has got you covered on that and then some!
  • You can access variables globally under the heap, and you can also resize variables when needed.

Cons of Heap

There are some negatives to using the heap, and these are just some of them that can affect programming speed and performance.

  • Execution times are slower than the stack, and it’s much harder to manage the heap’s memory in comparison to the stack.
  • Computations take longer to run on the heap than the stack, and using the heap can max out the RAM in your computer.

Stack vs. Heap: Comparisons

The major differences between stack and heap are many, and it’s good practice to see where each can be used optimally within the programming process. We will look at some pros and cons of using each one and then directly compare heap and stack below.

  • While a stack is used mainly for static memory allocation, a heap is used for dynamic memory allocation. One of the things stack and heap have in common is that they are both stored in a computer's RAM.
  • Stack memory management follows the LIFO (Last In First Out) order; storing variables creates space for new variables. On the other hand, the heap doesn't follow any order. It simply handles memory blocks dynamically.
  • Stack memory is automatically created at the same time as a thread. Meanwhile, memory in a heap is created as you create objects, which occupy space in the heap’s memory.
  • A stack is responsible for handling what you're executing in your code. On the other hand, a heap keeps track of your objects, i.e., it keeps track of all your data.

Stack vs. Heap: Head-to-Head Comparison Summary

Here's a quick breakdown of how the features look side-by-side between stack and heap with the data we've covered above.







Variable Deallocation

Not Required

Explicit Deallocation Is Required

Seek Access Time




Fixed Size

Resizing Is Available

Locality Of Reference

Automatic Compile Time Instructions


Pain Point

Memory Shortages

Memory Fragmentation


3 Different Ways - Simple Array-Based, Dynamic Memory, and Linked List Based

2 Different Ways - Array and Trees

Allocation and Deallocation

Automatically Done By Compiler Instructions

Manually Done By Programmer

Memory Allocation

One Contiguous Block

Any Random Order

Variable Resizing

Cannot Be Resized

Can Be Resized

Memory Size

Limited Size-Dependent On OS

No Limit On Memory Size

Variable Access

Local Variables Only

Access Variables Globally

Space Management

OS Efficient Space Management

Blocks Of Memory - FIFO Format

Access Speed

High-Speed Access

Slower Than Slack

Data Structure

Linear Data Structure

Hierarchical Data Structure

As you can see with this breakdown we have highlighted above, the answer to which is better lies within the programmer's ultimate goal in their project.


The age-old question of heap memory vs. stack memory is a hard one to answer.

If the programmer uses large structures or size arrays, they would be better off using the heap as you can allocate a large size to it. If the programmer just needs tiny variables that only need the quick ins and outs, then utilizing the stack would be the better choice. As it is, it’s user-dependent on which one would be better to use.

A better question for the programmer would be, which kind of “storage” memory would they like to have under pressure? A NAND Flash Memory stick (stack), or would they want to go with the old standard (heap)? As mentioned above, pros and cons exist for either selection.

By Aman Goel

Entrepreneur, Coder, Speed-cuber, Blogger, fan of Air crash investigation! Aman Goel is a Computer Science Graduate from IIT Bombay. Fascinated by the world of technology he went on to build his own start-up - AllinCall Research and Solutions to build the next generation of Artificial Intelligence, Machine Learning and Natural Language Processing based solutions to power businesses.

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