Stack vs Heap Memory in C++

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[@TheCherno]

Hope you guys enjoyed the video! A few notes: - to be clear, each program/process on our computer has its own stack/heap - each thread will create its own stack when it gets created, whereas the heap is shared amongst all threads

[@HazStepFTW]

So if your program is using multiple threads and there is memory which is created by one thread and needs to be read by another, for example, this memory would need to be allocated on the heap?

[@josephwalker208]

Are you going to cover multiple threads because I had I look and it seems simple but could get complicated

[@Puffadderr]

Yes. But that is really not good practice. When one thread is using something in heap allocated memory it has to lock the access to that memory until it doesn't need it anymore. So you really need to avoid using shared resources when using multiple threads. Threads are meant to do their own thing independent from other threads. You can use it to keep to keep track of like progress of all threads but continous access to resource is performance hit.

[@dXXPacmanXXb]

Objects like Enemies in a game should always be created on the heap right? Are the variables of this object then also on the heap or will they be on the stack?

[@olestrohm]

the variables inside the object are created inside the object's "memory space". So if you have an Enemy with an x and a y, it will allocate 8 bytes (2 ints = 2 * 4 bytes) and store the x and y in that space.

[@rawali1]

How is it that none of my teachers explained any of this during my whole bachelors degree.... this is brilliant! Thank you so much!

[@deadcells963]

Bad college ? 😅

[@malharjajoo7393]

not really, when you learn something for the first time, you might have been overwhelmed.

[@quicksilver5413]

I honestly fucking hate it when people make 'you taught better in 15 mins than my university was able to in 4 years' comments on these videos. Like bitch please it doesn't take 4 years to learn these you just haven't been paying attention

[@rawali1]

@@quicksilver5413 I didn't learn more in 15 minutes than in 4 years but this particular concept was not explained... my c++ teacher was absolute garbage. My java teacher was great, and a lot of that knowledge transfers over but... meh. java...

[@masihaahmadi7663]

tanks

[@dub16rider]

You are insanely efficient in explaining complex material, wow..., kudos.

[@felixchien1664]

Moreover he has very nice sweat pants! Kudos for that as well

[@davechan1281]

100%

[@eman5300]

Facts and he actually helps see the bigger picture instead of dwelling on definitions

[@jaminoes_]

I am pretty sure he speeds up his videos as well :-)

[@Earth-Worm-Tim]

I’m a Software Engineer, and my first SWE position was as a C++ developer which I learned predominantly from Cherno. I have an EE education, but I learned more from Cherno watching KZbin than I did in my Intro to C++ and Data Structures and Algorithms in C++ sequence in college. The Cherno is legit folks, but if you really wanna learn, you gotta start at the beginning of the playlist and go straight through watching EVERY VIDEO and coding along. C++ can be a frustrating language to learn, but if you learn C++ first, it’s cake learning ALL OTHER C-like languages. You’re the man Cherno!

[@mauricecooper9880]

That’s awesome! I’m a computer science major looking for my first C++ gig. Can you tell me more about how you got it? Thank you!

[@555gong9]

@@mauricecooper9880 Hello, I'm also looking for a job. Have you found one?

[@miteshsharma3106]

Happy birthday cherno!!!

[@mokshithpb7991]

This comment have 281 likes But 0 replies (except me)

[@paulu2862]

@@mokshithpb7991 2 now

[@projectvibe1226]

@@paulu2862 3 now

[@chauffeur1560]

@@projectvibe1226 4 now

[@Agent_Ax]

@@chauffeur1560 5 now

[@CaffeineForCode]

I like how you show why something is “expensive” or not very optimal instead of just saying it. You actually open the memory view or disassembly which is super useful! Thanks for the videos, they’re amazing!

[@igorthelight]

For all C# developers: "new" does not mean, that it will be allocated on the Heap (for C# program) MyClass c = new MyClass(); // Allocated on the Heap MyStruct s = new MyStruct(); // Allocated on the Stack (in most cases) That doesn't mean that structs are ALWAYS allocated on the Stack! Just most of the times. It depends. Read about "stackalloc" keyword and about "Span" and "ReadOnlySpan". They are great!

[@leixun]

*My takeaways:* 1. Both stack and heap memory are in RAM 0:47 2. How to allocate stack and heap memory 2:55 3. Stack memory allocation *stacks* data in the memory *in a row* and it is very fast 4:45 4. Heap memory allocation doesn't 7:49 5. Heap memory allocation needs to be freed manually by using "delete", whereas stack memory allocation is freed once the code is out of the current scope 8:47 6. How heap memory, "new" and "delete" work 10:27, allocating memory on the heap is slow

[@7guitarlover]

Its been 5 years since you uploaded and still it is one of the BEST video on the internet. Yours is a C++ Goldmine. could you please talk about your learning pedagogy of new things and especially C++. How did you gain so much clarity ?

[@MuhsinFatih]

This is by far the most complete lecture/tutorial whatever, I have seen in a very long time (possibly ever). You explained everything very clearly, demonstrated and tested them, yet did that all in 20 minutes. I am honestly surprised that this video doesn't have hundreds of thousands of views because you deserve that. Wish you the best!

[@logantcooper6]

"Stored in the caysh"

[@section9999]

caysh money dawg

[@tesla.8410]

I understood cage first, then caysh, then i understood that he actually means cache

[@theSassySquatch]

Dude I read that and spit out my drink I can't stop laughing

[@dameck9570]

Oh boy! I found a C++ video from you and now I'm stuck with video recommendations of your series. I appreciate that, but it's 22:30 and I wanna sleep... Seems like I wont

[@Markus_included]

same

[@blank-vw2sb]

Damn. It's 22:35 here. Awesome COINCIDENCE

[@jarektrojanowicz]

Thanks! One thing worth mentioning: We use heap for allocation during runtime and stack for allocation during compile time. It was mentioned somewhat in the video but I think it should be more emphasized.

[@mubin2026]

The stuff that I learned in this one single video is actually insane. like, I knew about most of the stuff that he said, but since all of it was taught to me over various courses, and bits and pieces at a time, I never really could figure out how it all fit in together...This such a wonderful explanation!! All of it is starting to kind of make sense now....damn lol

[@marioseis7692]

MAGISTER DIXIT...! I am no programmer but I have had basic lessons in C almost 30 years ago and now I am strugling to master at least the basics of C#, which I find sometimes a bit confusing and with a lot of rules. Sometimes I get some comfort watching basic C ++ videos, especially those that are very well explained and that go right to the point like yours.

[@TokisanGames]

I think this is my favorite video so far. I always wondered about the stack and heap differences. This is such a good explanation!

[@maxbardelang6097]

Very clear and easily accessible explanation, even the explaining with asssembler was just really supporting understanding.

[@dongyoungkim962]

hey cherno, your explanation of stack vs heap is amazing, no other youtube has evern been able to explain like this. ive come across heap and stack so many times but never got to really understand untill i watched your video today. thanky you so much!

[@jammerbammer1]

This is A+ content. For someone trying to learn to code there is a lot here and I will be re-watching this a couple of times and playing with the memory view in Visual Studio. Thanks.

[@ZzBiazZ]

Finally, you are back, your video always great, thank you !!

[@donha475]

This stuff is all great man. All of your C++ videos have been amazing so far.

[@ManaPie]

Hi, you could make a video explaining your way of structuring C++ projects: the way you separate your headers from source files, the way you organize your includes (precompiled header stdafx.h vs #ifndef guards), etc. What do you think? You're doing a great work, I've been learning a lot in your channel! Thanks!

[@patrikjankovics2113]

#pragma once I think, instead of ifndef guards.

[@xrarach]

@@patrikjankovics2113 This does not always work sadly. When you start having a medium or large-sized project (1M lines ) it will start to fail for some reason sadly, happened to me many times, thus using #ifndef

[@challengeyourmind3937]

@@patrikjankovics2113 #pragma once still can't prevent against including multiple headers within the same project because it excludes based on file system identity

[@Decco6306]

A trendy looking programmer that makes good quality programming tutorials on KZbin that doesn't use a mac? Respect.

[@kjes8639]

This was a very interesting video. Please, make more videos about the way C++ works. I am looking forward to seeing your video about CPU cache optimisation. Thank you, Cherno, love your vids.

[@svenbtb]

This was a really helpful video, thank you SO much. I appreciate that you show WHY the dynamic memory operations are more expensive and how it can be a performance boost to use the stack. So essentially, if you want something to have a longer lifetime, or if it's of a large size, then it's worth using the Heap, but if you're making a small simple variable that won't exist for a long time, it makes more sense to just use the stack, yeah?

[@Drtsaga]

Cherno, your tutorials are always great. I love that you pay attention to what you say. You always choose your words so that YOUR AUDIENCE understands what you say, and not so that you make sense to yourself. Thank you for the good work and congratulations. I am sure when you become worldwide famous these videos will get a lot more views. I have a question for you: How did you get to point that you know the material well enough to teach it? Who/What is **your** teacher? Other than sporadically making google searches and stumbling on documentation pages, do you regularly read books on C++? Do you constantly take classes? Do you continuously engage in competitions that keep your edge sharpe? How are you so good? I am not asking how are you productive. I just wander how do you keep this volume of knowledge in your head in such an order that becomes transferable to others. If I don't refresh something for a month (give or take) I surely forget it ... xD

[@nobytes2]

This is like asking a musician how she/he gets good lol. There's no freaking magic formula, is just practice and experience.

[@erikb4407]

@@nobytes2 I believe he's not asking for a magic formula. He wants to know the materials / instructors / methods The Cherno uses to learn and retain the vast amount of comp sci knowledge he teaches us. Practice and experience is correct, but *how* does he practice? Is it through competitions, work, reading books, classes, etc. Hope this helps

[@RemerexHD]

@@nobytes2 he just asking for tools

[@yellowlegend245]

Hi Cherno, nice explanation. Probably main point is not covered here. 1. Each function has its own stack area and not shared with other functions. Whereas heap is shared among all functions(within a thread as you said in a comment). 2. main use of heap is to allocate memory for pointer that is accessed across the functions. because once the functions scope is over, all stack variables are deallocated.

[@readingchess]

This is the first video I've watched and I wanted to say - Really well done! Such a top notch explanation. I'm subscribing for sure. Thanks again for taking the time to make these videos

[@franejelavic]

Hi Cherno, Could you maybe take a video about exceptions, and why you don't like them, how to avoid them and best practices. Also a good topic to talk about is unit testing and do you write tests in parallel with your development. Thanks for everything your doing here.

[@fouryeartransform3042]

I just nailed an interview question because of this and other videos. Thanks so much.

[@jioferno]

Clear, ,fluent and to the point explanation, thanks.

[@proton46]

Great video! Heap memory is a really complex topic.... It took me a long time to figure out how it works when I was writing my own memory manager! Thanks a lot for this!😃

[@annsgal2025]

One case for allocating memory on the heap is when one doesn’t know the size of data at compile time. STL containers are actually allocated on the heap internally because they grow in size dynamically when the preallocated size is not enough. So if you declare a vector on the stack, it is actually using the heap.

[@omarhatem_97]

i have been programming c++ for almost 7 years now , what makes you unique among other youtube channels or tutorials is that you are really so deep in learning and teaching the concepts . keep going man you are awesom !

[@shambhav9534]

7 years of typing and you don't know where the shift button is?

[@lucianodibernardo1546]

Awesome video !!!

[@mountgraph1403]

I learn so much over this channel thank you for the hard work!

[@Manalor6955]

I chuckle every time he pronounces cache.

[@philippebaque5157]

Many thanks for your effort and your very clear explanantions.

[@lijacky160]

I love you! YOU ARE SUPER HELPFUL !!!!!!!! KEEP THIS PASSION ON MAKING VIDEO. YOU ARE TALENTED

[@aadikarva]

Thanks @cherno for making these videos. Few follow-up Qs: 1. How many CPU cycles does Heap allocation take for each of the examples you talked about in the video above? 2. Can you start a series on OS basics like different types of memory, how it all works at the OS level etc. Thanks! :)

[@greob]

I'm not familiar with the concept of "CPU cache misses".

[@BlackJar72]

The CPU has several levels of caches that are much faster than ram on the motherboard, but the kind of memory is more expensive and has to fit in the CPU, so there is a lot less of it. When data is used accessed it will load the whole area of memory to the cache. If the next data it needs is in the same area it will already be loaded. If not you have a cache miss, so it has to load more from ram to cache, and that's slow. Basically when you have a cache miss the CPU has to sit on idle while waiting for the data -- if it was already in the cache it could just keeps going. It could make things 50 or 100 times slower if you have constant misses versus very few (if there is much data some will happen since only so much is moved at once). This is an advantage of arrays over linked lists -- linked lists cause lots of misses, which makes them much slower than arrays even at things they're better at in theory. That's simplified a bit, since different level of cache do have different speeds too, but that should give you the general idea.

[@xYuki91x]

@@BlackJar72 Thank you so much!!! Throughout the whole video I was wondering what "cache miss" means, I was so happy to find your explanation (which is very easy to understand, so kudos!)

[@mryup6100]

@@BlackJar72 May I ask where you learn about this. University? A book?

[@PatrickRobinsonZA]

@@mryup6100 experience

[@xrafter]

@@PatrickRobinsonZA Experience out ranks everything

[@ifeekesifeekes8166]

This video helped me a ton with interview questions, thank's so much!

[@sayeddileri3461]

Thank you for this video. I have been confused about stacks and heaps. You helped me so much. Time to practice 🙌🏽🙌🏽

[@KoderKapil]

Best content i found....Crazy, how it is simple and detailed 🔥.. Thank you

[@youssefel-mahdy922]

I loved the way you explained them through the code, thank you truly!

[@knofi7052]

Happy Birthday & Thank you very much for your great content! :)

[@edgaramiri]

You're the best man excellent explanation, thank you

[@MisterPubbs]

amazing and very clear video!

[@Jonathan-ex3sl]

Thank you so much for this content. It's been very useful for me.

[@anasahtsham4033]

THANK YOU SOOO MUCH MAN. VERY HELPFUL VIDEO, LOVED IT

[@bandolero818]

You are awesome Cherno! Thanks for your clear explanations!

[@feiyijiang9167]

wow, this video is wonderful! It answers a lot of my questions. Thank you Cherno!

[@davidpatry4195]

Thank you so much for your serie Cherno, I always learn alot watching you Happy holidays to you and your friends/family :)

[@rika9317]

This video is really easy to understand!! I didn't know that allocating memory in heap is such a heavy work, and didn't know why it's heavy. You showed me the way to ensure the reason, looking into the assembly code. I'm gonna consider using Visual Studio...

[@deepikagoyal07]

Its was super useful video. Thanks and Gratitude!!

[@rittenbrake1613]

I just enjoy u talking, very easy to absorb

[@dorkflassbury1164]

Great explanation. But I think we're missing an important difference between stack and heap memory. The size of stack memory to allocate is set at compile time whereas the size of heap memory is may be set in run time. Stack memory is more easy to manage and heap memory is more flexible (and maybe more efficient since actually may allocate just as much memory as you need when actually running your program).

[@xeturr]

Excellent refresher for me. Subscribed.

[@nickbejan4914]

Amazing explanation! Thank you!!

[@karimpeymani6569]

This is the best explanation video about Stack vs Heap I ever seen, Thanks man.

[@root0062]

I love how I get a good in depth explanation of stack & heap. Dare I say better explained than my proff. And at the end of the video I go. Wow! I have the same couch!

[@krisitak]

Next level videos. Thank you!

[@AlaaAreesPhoenix]

Thanks a lot man your videos are so helpful , keep going 💙💙

[@pablorodrigues9811]

Thank you for this really great content, Cherno!

[@vectoralphaSec]

So always allocate on the stack rather than the heap whenever possible until you can't. Got it.

[@dafdaf4052]

Very nice and informative, I am kinda addicted to your videos gj.

[@neiltsakatsa]

Thanks Cherno ! I was wondering if sometime you could dive into Windows Forms Applications using Visual C++ :-). I'm really enjoying your tutorials man !

[@platin2148]

Neil Tsakatsa Don’t think that we will ever use this api same with WinForms you probably should look at C++/Winrt wich is more native than the CLR version wich has an ugly syntax and is very slow compared to Nativ C++.

[@HazemSaleh]

You are a king. Excellent explanation, thank you.

[@WelcomeToSex101]

You should talk about move semantics. I found that it is relatively new topic and it's kind of confusing.

[@Qdouble]

Amazing video! Thanks. I just subbed.

[@marindraganov8765]

Pal, thanks a lot! It is like putting me in a new dimension with my coding! Now I have a vague idea why my projects work the way they do! Coming from Python/C# background this video is an eye opener! EDIT: Typo.

[@sheepcommander_]

this video was helpful enough im almost willing to overlook Caysh

[@lukaspetrikas6320]

Your a very clever guy. I find your videos extremely helpful

[@ChamAntonio]

still such an amazing and practical video now it's 2021.

[@dxlge]

amazing, explained really well and in a clean way

[@alexseresalex1843]

I don't really comment on videos, but this is some extra high quality stuff

[@daluwang2112]

Thanks for explaining this sooooo clearly and in an easy way!!!!! very useful!

[@albertkiefel]

Very well explained, very good examples!

[@shruthiabirami7406]

Awesome video😀 understood clearly... Kudos❤

[@codastudiode]

dude, you're awesome! I've learned it like a piece of cake!

[@Jonny-op3wr]

Just subscribed. Enjoyed the content. 😇

[@MrDarkyosh]

your videos have been very helpful to me. I hope things are going good for you Cherno :-)

[@marcelbarbosa281]

Sick bro

[@relytheone853]

I enjoyed the video. Thank you!

[@dream_emulator]

Wow. This guy is next level and then some. 🔥

[@TheShorterboy]

having written malloc's for embedded systems doing all the merges is what takes time, you can do it in a thread but that's still time you are stealing from a core and on embedded you didn't have any spare, abstracting your pointers is a way to get around this but it creates funky code no one wants to write

[@LarryPeteet]

Very Helpful, Thanks!

[@dan110024]

Random fun fact - 99% of Rollercoaster Tycoon was written in assembly by a single developer. Getting an understanding of even a fraction of what goes on here, it's insane to think about how good Sawyer, the dev, was.

[@milosz-barylowicz]

Maybe you can cover rvalue/lvalue topic it is pretty confusing or move semantics.

[@MsJavaWolf]

@@Franckbery IS that all though? I always though there were like exceptions to that simple explanation.

[@mateuszabramek7015]

Done

[@minderiskrir989]

We really do need a CPU cache optimization video.. & thank you The Cherno for your informative/educational videos.

[@zniverse]

Your video is always great. Thank you.

[@ErichDAtriGuiran1]

thanks dude, good explanation

[@petersenglish]

This was super interesting. However, thanks to you, I have spent hours looking at assembly code trying to figure out what it is doing.

[@L1Q]

finally! the no-bullshit explatation! 🙏

[@duckcluck123]

Wow, this was incredibly incredibly insightful

[@basharTheSoftwareEngineer]

words cant describe this video thanks for helping

[@koungmeng]

3:08 you can use: int* hvalue = new int(5); //save 1 line of code xD

[@smileynetsmileynet7922]

Right, like using a built-in constructor.

[@Djzaamir]

Finally dude , its been some time since your last video on C++

[@haznoskill]

A lot of useful knowledge, thanks.

[@footballCartoon91]

@3:12 It is a worthwhile to explain that the variable name must be declared differently between variable stored in stack and in heap

[@footballCartoon91]

@Artem Katerynych In the example he used int value; and int *hvalue; both exist on the stack while the value of int *hvalue exist on the heap.. That is from what I understand him saying.