Stack vs Heap Memory - Simple Explanation

I take a look at Stack and Heap Memory and how it affects your application. Knowing how memory is handled in your application can help you understand your variables' scopes.
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⏳ TIMESTAMPS
00:00 Introduction
00:18 Three main parts
00:28 Stack data structure
00:51 Call stack
01:19 Heap differences
01:50 Variable storage rules
01:58 Value types and reference types
02:23 Local variables
02:40 Reference types on heap
02:57 Value types on heap
03:20 Garbage collector
03:53 Exceptions to the rule
04:40 Asynchronous methods
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🧑‍💻WHO AM I
I'm Alex, a Software Developer and KZbin working in the UK. I make videos about software development to help developers with the skills they need to be senior developers. As well as this KZbin Channel, I also write articles on my website (alexhyett.com) as well as write a regular newsletter that contains some thoughts to help aspiring developers.
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#coding #programming #developer

[@michaeltheisen]

These ideas were saved in my head as a sequence of words for the entirety of my undergrad. If 5 short minutes you managed to actually help me understand a huge gap in my understanding. Thank you so much.

[@alexhyettdev]

You're welcome Michael, I am glad it helped.

[@saumyojitdas4212]

​@@alexhyettdev public class Main { String s = "ABC"; public static void main(String[] args) { Main obj = new Main() ; System.out.println(obj.s); } } in this above code String object is created in heap and also of class. So 2 objects in heap. But isn't the string object Abc resides inside class object in the heap?that's why we are calling it obj.s

[@rembautimes8808]

Good video very in-depth

[@crazychase443]

i feel the exact same way!! this random collection of words and statements now i feel like concrete concepts in my brain

[@based6457]

Perfect, really good explanation. Thank you!

[@JakeeReacher]

Alex, you made my day. I would call you one of the best instructors! Your explanations are flawless. You explain perfectly in context. For instance, where you explain why variables are not accessible outside the method.

[@alexhyettdev]

Jake, you made my day! Thank you for the lovely comment. I am glad you found it helpful!

[@bitwisedevs469]

Finally a much simpler with actual sample code that explain the whole stack and heap stuff. Now I understand why and when OOM occurs in app, the usual suggestion is to increase heap size but said to be slow or when we do recursion recklessly we get stackoverflow.

[@benessilfie]

This explanation was exactly what I needed! thank you Alex

[@alexhyettdev]

You’re welcome I am glad it helped!

[@sonederbr]

The best explanation/animation ever.

[@alexhyettdev]

Thank you!

[@kohltonpeterson3287]

This is one of the best programming related videos I have ever watched. It cleared up so much of my confusion in C++.

[@alexhyettdev]

Thank you!

[@luminuslux]

Not gonna lie, i cant state enough how explanations like this can massively improve your understanding of why code works the way it does. Just learning to code is one thing, but understanding whats behind all of it and WHY whatever thing actually is happening, can definitly up your game. Im not a pro by any means, but i think stuff like this is very important. The visual presentation also makes it way easier to follow and connect the concepts - so thx for that 😊

[@alexhyettdev]

Thank you, I am glad you enjoyed the video. I find it helps with remembering everything as well. If you can understand something then it tends to stick in your mind a bit better.

[@csanid1]

hey this is an excellent video! i'd never thought or read about the link between variable scope and memory. thank you so much!

[@patrickmccarthy7124]

The analogy of a stack of books provided much needed clarity for me. I appreciate the video mate!

[@alexhyettdev]

You’re welcome, I am glad it was helpful.

[@alexsal6069]

This is an excellent video about how the memory works, I love the last part about asynchronous methods. Thank you for this awesome content. I wish you could speak more about asynchronous functions. 😃

[@balajia.t1487]

A nice and concise explanation . Wishing you all the best for better reach of your subsequent tutorials so a lot from community would benefit

[@amalekilawlor2922]

Wow this was an incredible series of topics, thank you!

[@alexhyettdev]

Thanks, I’m glad you enjoyed it!

[@Mythical_Beastinator]

Very well explained. Thank you!

[@alexhyettdev]

Thank you, I am glad you liked it!

[@Freepackman]

absolutely brilliant explanation, thanks a lot

[@alexhyettdev]

Thanks, I am glad it was useful!

[@SSn0wx]

Great explanation. I do mostly web development, but I've been getting into low-level programming recently, and your video really helped me reach out into my bucket of programming concepts and rearrange a bunch of previous knowledge I had about computers into something more clear and concise. Thanks!

[@alexhyettdev]

You're welcome, glad I could help!

[@timi_t_codes]

Thanks for this simple and straight to the point explanation

[@alexhyettdev]

You’re welcome!

[@kasunsaumya3151]

Simply love your explanations.. Clean and deep..

[@alexhyettdev]

Thank you! 🙏

[@potatopotato4676]

Your explanations are immaculate! You'll definitely make it big if you want to. I am glad I caught your channel early at 18.4k subscribers

[@alexhyettdev]

I appreciate that! Will be making more videos soon.

[@polimorphic13]

Excellent explanation. Thank you so much.

[@dorianneto2859]

Such an intuitive and simple explanation!

[@alexhyettdev]

Thank you, I am glad it was helpful.

[@paulventura3118]

Great explanation! Thanks Alex!

[@alexhyettdev]

You’re welcome!

[@triphazard2906]

lovely explanation, thank you for this

[@alexhyettdev]

You’re welcome! I am glad it was useful.

[@davidjiang7929]

Thanks for the great explanations!

[@wajdwael8775]

That is a great, clear, and easy explanation, thank you.

[@may8128]

Loved the explanation !

[@alexhyettdev]

Thank you! I am glad it was helpful.

[@cmaz6132]

Great tutorial, it really helped me! Keep it up👍

[@alexhyettdev]

Thank you! I am glad you found it helpful.

[@nomymathieu-petrin5672]

A hidden gem !!! Thanks you so much, I understand it so much better now !!!!

[@alexhyettdev]

I am glad it helped!

[@gavinmeeker287]

Really great video! This helped so much

[@alexhyettdev]

Thank you I appreciate the kind words. I am glad it was helpful.

[@milehighgaragespeedshop1065]

Excellent explainer and graphics THX

[@alexhyettdev]

You’re welcome, I am glad you like it.

[@mehtubbhai9709]

@Alex Hyett As always, you give the best explanation of whatever programming topics that you cover. Please keep up the great work and keep the content coming. I'm a fan :)

[@alexhyettdev]

Thank you, I am glad you like them!

[@chocolate_Almonds]

Dude, that was awesome. You explained what I tried to wrap my head around in college courses, in 5 minutes. ily :)

[@alexhyettdev]

Thank you! 👍

[@MarcoLenzo]

This video was very good! I really like the way you explain!

[@alexhyettdev]

Thank you! I am glad you liked it.

[@vfryhn2]

Such a great explanation

[@alexhyettdev]

Thank you! I am glad you liked it.

[@billbasdras5568]

That's good stuff ❤ subscribed

[@scubagoblin]

Reading a book right now that explains this concept rather poorly over 20 pages. You managed to grant me understanding in 5 minutes, and now I can continue reading past the chapter. Thank you, great explanation!

[@alexhyettdev]

You’re welcome! I am glad I could help you understand it. Hopefully more fun than reading 20 pages of that book.

[@iDeveloper92]

Excellent breakdown!

[@alexhyettdev]

Thank you!

[@JanosTech]

Fantastic explanation, thanks mate!

[@alexhyettdev]

You’re welcome! I am glad you liked it.

[@0bsy96]

My jaw dropped when you explained what happens to variables declared in the stack, I never made the connection between this fact and the scope of variables, thank you soooo much !!!

[@nikolabosevski1435]

Samee heree, I've never even thought of why we couldn't call variables from different scopes, i just took it for granted this opened my eyes

[@TheHermitProcess]

I'd be extremely weary of taking this for fact. It is up to the compiler to generate scoping rules, as far as I know. Look into it a bit more.

[@Tanessok]

Thank you sir. Good Explanation. Please, I wish you make a video on "Why in Java, Do Local Variables Used in Lambdas Have to Be Final or Effectively Final?" and please make the explanations at the memory level too, so we can understand all the mechanics behind it.

[@gantushigsaruul2489]

Thank you for easy to understand and great video

[@JHatLpool]

Very nice explanation. Thanks !

[@MrHussien66]

you actually help me understand a lot ,thank you sir

[@alexhyettdev]

You’re welcome!

[@AXkj3mmy]

Thank you! This was great

[@i_am_dumb1070]

Thank you very much i was not able to understand this concept even after reading and watching a lot of videos now i have a good understanding of this

[@alexhyettdev]

That’s great! I am glad I helped.

[@i_am_dumb1070]

@@alexhyettdev if possible can you please explain the anonymous function part i didn't get it

[@Ali_Pxll]

Man you're a savior thanks for the clear explanation

[@alexhyettdev]

Thanks, glad I could help

[@johndzikunu9986]

This is good. Have learned some things I could not know in a year.

[@alexhyettdev]

That’s great I am glad you learned something from it. Thank you for commenting.

[@younesmdarhrialaoui643]

Great explanation!

[@alexhyettdev]

Thanks! I’m glad it was helpful!

[@miladfahimi4787]

that was flawless thanks a million man

[@alexhyettdev]

You're welcome, I am glad you liked it.

[@nargesdeypir4579]

Hey man, awesome awesome tutorial

[@alexhyettdev]

Thank you!

[@GG-sw9vm]

that was a clean description of stack and heap. Never knew about anonymous function being a heap, but it makes sense

[@alexhyettdev]

Thanks I am glad you liked it 👍

[@juliaclaire68]

thank you! very clear

[@alexhyettdev]

You're welcome Julia, thank you for commenting.

[@ragtop63]

Well done! Very good video.

[@tannguyen_91]

amazing, this help me understand everything

[@jacobL1172]

Learning Redux right now, so very helpful! Definitely subscribing.

[@alexhyettdev]

Awesome, thank you!

[@alireza.m]

Thanks for the video

[@alexhyettdev]

You’re welcome!

[@hamidouhsemix8940]

Nice video, very helpful

[@alexhyettdev]

You’re welcome, thanks for commenting.

[@johnolawale2749]

Finally, i now understand the differences between these two. Thank you for the video

[@alexhyettdev]

You're welcome 😊

[@tibebetech4867]

Thank you!

[@alexhyettdev]

You're welcome, I am glad you liked my video.

[@ukaszkiepas57]

Thank you very much mate. Clear : )

[@Fernando-du5uj]

You're great. Thanks

[@rafaelstrack5858]

Great video!

[@Black_Cats_]

Good video. One question: In the case of results from asynchronous methods, once the asynchronous function completes, who cleans up the result in the heap that was left over by the async function?

[@alexhyettdev]

Generally they will be cleaned up by the garbage collector in the same way other objects on the heap are.

[@Black_Cats_]

@@alexhyettdev thanks for your response

[@shadon_official2510]

this video is gold! wow!

[@alexhyettdev]

Thank you!

[@Soupie62]

How does garbage collection handle memory fragmentation? Is there a heap defrag utility? Do you wipe the heap when a program ends? What is multiple programs / threads run concurrently? Now I need to check the rest of your videos for answers. Thank you for starting my journey.

[@EugeneDaveAstator]

Awesome video! Id like to add that in csharp async doesnt always equal multithreading, and since it uses internal statemachine which is a class, asyncs may get allocated on the heap

[@alexhyettdev]

Yes it’s a good point!

[@alejandropoirier6493]

Amazing explanation, greetings from Chile

[@alexhyettdev]

Thank you! Hi 👋 from UK 🇬🇧

[@DiogoSilva-xx8nz]

neat explanation, ty

[@alexhyettdev]

Thank you. Thanks for commenting!

[@sunnypatel1045]

Nice video pal. I love to see a video about boxing and unboxing.

[@alexhyettdev]

Thanks! Sure I will add it to my list.

[@PalasBrown]

thanks for your video

[@alexhyettdev]

You're welcome, I am glad you liked it!

[@AdrianTregoning]

Create more content, you'll be to a million subscribers within a few short years I have no doubt. Your content is pure gold, thank you for explaining this so clearly.

[@alexhyettdev]

Thank you 🤞🏻. Regular content will be back again in September. I have had some family commitments that has put a stopper to my videos this month.

[@AdrianTregoning]

@@alexhyettdev fully understand. Good luck! I quit my full time job as a mechanical engineer to become a programmer/coder of sorts. Bit tough being a student at age 41 but for me I made the decision to ultimately spend more time with my family. Have a super day further.

[@rembautimes8808]

Loved the garbage collector animation. Very nice and funny

[@user-ej8tt6lr2k]

Great Vid

[@petarkolev6928]

Such a precious channel!!! Instant sub from me 🍻🍻

[@lachlankitchen528]

Brilliant video

[@alexhyettdev]

Thank you!

[@joshuafashe9437]

God bless you man.

[@alexhyettdev]

Thank you! 🤩

[@ivandrofly]

Nice explanation :)

[@alexhyettdev]

Thanks 🙂

[@ronz91]

Great video

[@alexhyettdev]

Thank you!

[@yassinekharkhach4889]

you are the king

[@alexhyettdev]

Thanks man 👑!

[@kwaku_2023]

@4:23 what do you mean by the anonymous function is pushed on top of the stack and not have access to what previous level down? You mean even variables within main?

[@leeeric6292]

Many thanks to your video, this KZbin is valuable, so I read word by word carefully. And I find at 03:55, about the static variable, which is different from what you mentioned in your flvog (the link you provide in descriptions). In ur flvog, in para "where do static variable live", there you said static variables even if they are value types are not stored on the stack or the heap...need clarify? Thanks.

[@alexhyettdev]

Thanks for spotting the discrepancy! I need to update my blog to make things clearer. Basically it is an implementation detail. In C# static variables are part of the MethodTables on the "High Frequency Heap". Which is a special part of the Heap memory for static variables and internal data structures. In C and C++ they are stored on the Data Segment, which is a special part of the memory for storing static variables and internal data structures. :) Sound familiar? If you look up Data Segment and High Frequency Heap they are both in the same place in memory. By the looks of things they are just slightly different implementations of the same thing. There is an old article here that explains it in depth: web.archive.org/web/20140724084944/msdn.microsoft.com/en-us/magazine/cc163791.aspx Jon Skeet also has a good article on it as well: jonskeet.uk/csharp/memory.html

[@leeeric6292]

@@alexhyettdev Thanks for your response and your KZbin.

[@nobody-dy6ld]

thank you.

[@alexhyettdev]

You’re welcome!

[@hermanheinz33]

Very good video

[@alexhyettdev]

Thank you! I am glad you enjoyed it.

[@harrylyod3402]

Noice explanation thanks mate

[@alexhyettdev]

Glad it helped

[@Cruz0e]

what does "heap has higher overheads" mean...? higher cost? I assume (seeing that little 'watch' with pointer at high) that you mean for example it's slower, because it's more complicated for the "machine code" to add to the heap?

[@alexhyettdev]

Yes higher overheads as in performance. It is slower to add to the heap compared to the stack.

[@aelesbao]

This video needs to be promoted higher on KZbin. Anyone who wants to learn Rust should start from here before diving into the borrow checker.

[@alexhyettdev]

Thank you. I am glad it is useful for people learning Rust as well. Some of the C# references might not be applicable but hopefully the rest is. I need to learn rust as well actually!

[@Cruz0e]

"In a previous video" you talked about value type and reference type... can we get a link to that? I found a playlist but this is the first video in it.. there is no previous video

[@alexhyettdev]

It was very briefly here: kzbin.info/www/bejne/pnyplImpZ62cmKM

[@Misteribel]

3:01 small correction. A const is NOT allocated on the heap. In fact, it's embedded on the call site at compile time (in C#/F#/VB), the reference is removed (you can test this: create a const in another lib, reference and use it in your lib. Compile. Now update the const in the referenced lib and recompile, but do not recompile your lib. You'll see it did not change on the call site). What you probably want is readonly, which, in your example at 3:01, would then be allocated on the heap.

[@wajdwael8775]

Can you recommend 2 or more books on memory and data structures?

[@217-sritejrajulu6]

awesome

[@alexhyettdev]

Thank you!

[@abdulhaseeb114]

How could I assign which data must store in which memory?

[@alexhyettdev]

You can't. It is decided by the application runtime.

[@abdulhaseeb114]

Thank Alex, So in that case , then why I should know about the memory allocation if I can't able to assign.. There must be a reason pls help me understand..

[@WhiteSiroi]

thank you

[@alexhyettdev]

You're welcome!

[@xetz]

very nice video

[@aligharaibeh3761]

Heap is the same as heap data structure for prioritizing values?

[@TheChyamp]

Aren't static variables stored in the data segment? Not sure if any language stores static variables in the heap?

[@alexhyettdev]

It seems to depend on the language. For C# they are stored in the heap from what i have read. C and C++ you right it is the data segment.

[@vikingghost117]

I haven't coded in over a year. I had a dream where I was traversing a world on some quest to explain stack vs heap to all these people getting it wrong, and I knew they were wrong but didn't know why. Soon as I woke up I came here. Now I can sleep at night again. Thanks! 😂 It was an..(Explain you're a nerd without saying you're a nerd XD)... moment.

[@alexhyettdev]

I am glad I can help you sleep at night! 😂

[@doctrina3344]

I just have one question about this, are the heap and the stack RAM? Does ROM have them too?

[@alexhyettdev]

Yes Stack and Heap are stored in the RAM. ROM doesn't have a stack or heap as ROM is Read Only Memory. It is written once and can't be changed. It is typically used for low level code such as the BIOS. Although even that is usually stored on Electronically Erasable ROM (EEROM) so that it can be updated. All of the applications on your computer including the OS will use the RAM. Stack and Heap are just ways in which the memory is structured to store your application code.

[@dflosounds]

Great explanation! Thank you! My only bit of feedback would be to stay on the graphic visualizations longer. The constant switching between the visualizations and the shot of you talking is a bit jarring and makes it harder to focus.

[@tylersmith8245]

Incredible. Even though I've been a professional developer for six years, I was having a crisis of confidence tonight because I've worked with languages where I never have to worry about this directly. I was asking myself, "Do I even know anything about computers if I don't know the difference between the stack and the heap?" Five minutes and twenty-seven seconds later, I feel like I have a solid understanding of the difference and I'd be capable of talking about this intelligently. Thank you 🙏

[@alexhyettdev]

I have been a developer for 12 years and I went through exactly the same thought process before making this video. I am really glad it helped you.

[@___gg421]

Same here just went through a training where some memory management stuff was covered and I felt like an imposter. This made it all make sense

[@frankkim9178]

Can't find the reference type and value type video. Can you please share the link/ Thanks!

[@alexhyettdev]

It was very briefly here: kzbin.info/www/bejne/pnyplImpZ62cmKM I probably need to do a separate video on them to be honest.

[@frankkim9178]

@@alexhyettdev I like the way you explain the concepts!! Would to love see the a video about pass by value and pass by reference with more examples.