Pointers and Dynamic Memory in C++ (Memory Management)
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- เผยแพร่เมื่อ 24 ก.ย. 2024
- An introduction to using dynamic memory in C++.
Concepts:
Why we may need to allocate memory dynamically?
new operator
heap (free store)
pointers to reference dynamically allocated memory
delete operator
garbage
dangling pointers
thanks man, hats off sir.
I wonder why we pay our universities and end up learning free on TH-cam😒
Because there are stupid people out there want paper signed by University
@@Guest-gy9vp hell yeah
Why job market wants that fucking papr signed by fucking garbage university
It's because you guys never concentrate during your lecture.
Don't know if you are trolling or for real.. Universities exist to guarantee a certain quality standard, if you have a degree there is a guarantee that you meet those standards and know specific things.. There is no standard for people who learn online, they might be geniuses, but could also be "garbage" programmers.. ;)
@@DonSanchezDK but as an employer you can make interviews or tests ,if the employee pass ....that is a proof he know things necessary for the job...so there goes the purpose of college !
DUDE I literally got a 100 on my exam because it was based off of memory diagram questions. Thank you!
Nice 👍🙂
@Abhinav Rao LMAO
@Abhinav Rao bruh moment
@Abhinav Rao do u think people should work infront of the computer 24/7 to use their programming knowledge?
@Harsita's Kitchen do you code while cooking?
at 6:48 he crack me up every time.
Describing all the code I've ever written.
hahahahahahhaha
Super clean and easy explanation. Absolute masterpiece if anyone wants to understand pointers, dynamic memory allocation, stack and heap.
Just started programming and c++, memory was the first topic that I would first struggle to understand and get my head around and this video really helped :) thank you so much
Since C++11 You should not set a pointer to NULL, but rather to "nullptr".
+Peterolen or use 0 and use it in c++1002059
=0 isjust fine anyway.
Zoran Jovanov Not really. It was replaced for a reason. Imagine having two functions, void Func(string* aStr) and an overloaded version called void Func(int aNum).
If I call Func(0) or Func(NULL), Func(int aNum) will be called. But if we call Func(nullptr), then Func(string* aStr) will be called, which we want as we're dealing with pointers.
NULL is just constant of 0 difference is NULL is defined with #define and nullptr is a const variable it was replace just to tell you that you are assigning it to pointer and to avoid some memory leaks :)
Scias
yes but i ment only when u delete pointer so it wont be dangling =0 is just fine.
i ‘ve watched many best tutorials but this one made my way clear that i won’t ever forget how stuffs are allocated in the memory. Thanks sir
Very informative! Really liked your drawing of the 'heap' and the 'stack'. Made it much easier to understand what is going on.
This video is 7 years old and it is the best explanation I've yet encountered on this topic. Thanks.
I have never seen anyone explain this more clearly in my life. You are amazing!
I've been reading Dr. Bjarne Stroustrup's book on Programming and referring to your videos often. I must say that I wouldn't probably be able to go through that complex book if it weren't for your clear, really lucid explanation of concepts. Thank you so much!
Your efforts are paying off for more than 10 years. This video helped me a lot. Thanks !
finally understood the concept...this video helped me a lot...
I was debating dropping my major until i found your videos, thanks for the help/motivation!
i got the clear idea of what is heap and how to handle new/delete operators and that too dangling pointers and garbage collection. Thanks for this lecture.
Those illustrations were SOOOOO helpful. Thanks!
This was the best educational video of explaining pointer and dynamic memory. Everything about pointer and dynamic memory is so much clearer now. Cheers !
Thank you so much for the tutorial. Dynamic Memory Allocation has been kind of a plateau in my C++ learning, and you explained it very concisely. Very well done.
the best 13 minutes of my life
The stack memory is managed by the program/compiler
Dangling pointer = pointer that points to something that no longer exists.
you can assign a dangling pointer the value NULL or 0
When a function exits its memory on the stack is deleted.
best pointer explanation ever :D
Excellent explanation with the graphics. Please make more videos. Thank you
Woww😲 had been struggling with this topic for months.. well explained..Tysm.. you're awesom!!!
He is so simple in explaining complex concepts. thank you
One of the best explained topic I ever seen
best c++ fundamental videos on youtube
Thank you very much.
You really helped me. May God guide you and increase your knowledge .
Taking reference from your videos and C++ Primer both, best learning combo ever!
Thank you so much. I watched a few of your videos today, and I found them very helpful. Clear and concise, really impressive!
I removed a comment by mistake. Apologies to the user that left the nice comment. I had replied "Thanks!" to your comment under my other account and wanted to reply under my ReelLearning account. Deleting my comment, deleted your comment, for some reason.
This helps me to understand the operations of 'new' and 'delete' . Thanks.
Excellent for someone working closer to the hardware and memory!! Great video. Keep it up
The best video I've ever watched about pointers
This is a great video, the drawings really help to make the concepts and idea take concrete form for a begginer
Such an amazing amazing amazing amazing amazing amazing tutorial...hats off
Thanks for the video its NUTS & BOLTS :). I am trying to learn how to make a program and everyone says C++ is powerful because of memory management, but now that I am learning it they keep getting away from the nuts and bolts and pretty soon everyone is talking about packaging everything into things already programmed in other things... boxes within boxes and which box to use... Before too long I don't even know what nuts and bolts are actually in the boxes or anything from anything. So thanks
Thank you so much! I finally understand why pointers are useful! I have been facepalming over them ever since I first read about them.
Excellent video. You really capture the big ideas well.
I love the drawings!
You helped me understand what a stack frame is! Thanks!
Wow. explained in such simple terms. Thank you so much.
Thank you so much bro! Your drawing and interpretation of heap & stack made me understand the whole thing :D
4:31 That voice crack though haha
I'm actually kinda scared to start practicing on pointers...
I don't really understand them to well...much reading up on to do. But the last example you did with the function sparked a question. If you close the program, then what happens to the garbage? Does it get deleted? Cleared?
When you start your program - OS allocates some memory for it, then your application messes with memory that it is given(storing everything it needs - text, globals, heap, and stack). After it terminates, OS is responsible for cleaning up the mess, so memory will be freed
1. Theoretically - yes, practically - not really. The address that contains garbage is still occupied, so nothing will be written there by the program or OS automatically unless you use a delete operator to tell that the memory address is now available for use (it doesn't really mean that the value is deleted, it might still be there it just marks the address as available and might or might not be used again). The only way to replace the value guaranteed is to get the address, and to do so you have to manually increment memory addresses and check whats in there, but another problem rises - how would you know what is a garbage value? For example 53453453453 can mean garbage or actual value, it can be an integer that fits entirely in a single memory address or can only be a portion of a large object that continues in the next address. That leads to your next question
2. This one is even more complicated, since it depends on implementation of memory management in OS, in general heap is not guaranteed to be contiguous, however more than often you will see the opposite if you write a program to demonstrate it (the program is tiny and will terminate quick so the whole heap will be within certain range). Also all(?) modern OS use virtual memory technique, meaning that the memory used by a process is different from actual physical addresses where stuff is stored, and on top of all that paging and swapping are used to move memory around.
Hope that helps a little bit, also note that I am not a C++ guru and might be wrong on something. Please read more about terms I used in my answer to get a better undestanding
You dont have to start with pointers, they are not needed at all until well into mid-tier knowledge.
When you need to move beyond the memory limit of a stack you will know 100% enough.
History
In 1955, Soviet computer scientist Kateryna Yushchenko invented the Address programming language that made possible indirect addressing and addresses of the highest rank - analogous to pointers. This language was widely used on the Soviet Union computers. However, it was unknown outside the Soviet Union and usually Harold Lawson is credited with the invention, in 1964, of the pointer.[2] In 2000, Lawson was presented the Computer Pioneer Award by the IEEE "[f]or inventing the pointer variable and introducing this concept into PL/I, thus providing for the first time, the capability to flexibly treat linked lists in a general-purpose high-level language".[3] His seminal paper on the concepts appeared in the June 1967 issue of CACM entitled: PL/I List Processing. According to the Oxford English Dictionary, the word pointer first appeared in print as a stack pointer in a technical memorandum by the System Development Corporation.
en.wikipedia.org/wiki/Pointer_(computer_programming)#History
Thank you so much for offering high quality tutorials!
+Forever Alone Studying for the CS final? lol
What?
+Ferris Bueller yes, this is part of my last assignment and will make up most of the final
Very informative video! Thank you so much!
The "garbage", i guess is called "memory leak". Good video!
Thanks for the video! It's a lot easier to program codes in c++ using memory allocation with your explanation visuals in mind! Thanks a lot! :D
very precise and informative!!~ thank you so much!!
very clear clarification. Thanks man
This was crystal clear .Thanks
Thanks for such an easy explanation
great job! thanks so much for making this video :) helped me with my homework
thank you so much I never get to understand pointer as I did this time, thank you again
Rockstar should learn this...
I love your tutorials. You explain thing soooooooooooo clear. Thank you soooooooooooooooooooooooo much.
Yea nullptr uses in C++ from the book. Very good video very clear. Better than the book.
very great explaination. thank you
Agree, finally understood the concept
a legendary explanation. thank you sir.
This was a great explanation. Thank you!
I loved your explanation. Thank you!
Holly shit you explaint it like no other, literally 15 min and I understand it all now! Thank you!! :D
this video explains alot. however, as a beginning, I still have a few questions.1. Variables stored in the stack DO have variable names and variables stored in the heap DO NOT have variable names, correct?2. What is the advantage/disadvantage of storing variables in the stack vs. in the heap?3. This is probably a stupid question, but why is it necessary to have a stack and a heap? Why can they not be considered one and the same? Then pointers would not be necessary?
Short and informative, thank you!
Very informative video! Keep it up.
I HAVE A QUESTION!
this is my code:
____________________________________________________________
int *p = new int(3);
cout
got it. thank you
Great explanation.
You are incredible! Great presentation! Keep it up!
Awesome explanation
I'm extremely new to programming. But to summarize heap and stack, very simplistically, the stack is limited in terms of memory to the program. If for some reason you don't want to bog down your program by overusing your available stack memory, or risk overusing your memory and crashing the program via a stack overflow, assigning parts of the code to the heap temporarily allows you to avoid all of this? It's like having a glass, and you're limited to how much water you can pour in it, but if you need more water than your glass possibly can accomodate, you can pour it into another cup and sit it beside your main glass. Is this kind of accurate??? Thanks for the awesome video!!!!!!!!!
You may have advanced to the level of senior programmer by now,😊
Let's reverse the question back to you: is this accurate?
OOOOHHH MYYY GAAAADD! Pointer's too simple now that I learned it from u
excellent explanation!
Greate explanation.
I finally understand this concept
very useful video....carry on
Would it be more appropriate to call it a “memory leak” than “garbage”?
Thanks man, really good explanation!
Just a doubt, in the function x() when you don't use delete to deallocate memory in spite of being empty (because you just did new int, instead of new int(10)), it's not the same as if it wasn't allocated and that way stay free?, or exist some mechanism that prevents use that section of memory due to the lack of a delete statement for the same pointer that was declared with the new operator?, for the rest,it was completely pleasant to watch, thank you for share knowledge!, greetings from Perú.
outstanding sir.
really nice article about memory
Amazing explanation. Thanks
Very Useful. Thankyou
Please come back bro, we need ya 😥
Wow great video! I completely get it now :) Doing a quick review, haven't touched this material in a while haha
Thank you! You really explained it well and it helps me a lot in studying :)
I wish you referenced memory locations as an explicit hex value, such as "0x500" instead of "500". Instead, you have a bunch of ints (some that are actual int values and others that are actually memory addresses) all over the place and could confuse people.
Jimmy Watson I get confused until see your comment, thank you. :）
Jimmy Watson Yes. Well done for pointing that out.
he "pointed" it out, eh?
get it? get it?
Both 500 and 0x1F4 would reference the same memory location..
I understand your idea though :)
Thank you so much for your effort man! your doing such a great job...
I have only one question, is there any way to get your notes for the videos you ?
Great explanation. Is it possible to find size of the reserved memory for a specific variable in heap? For stack, it is sizeof() but what would be the case for heap????
Newbie here, why would you use a variable in the heap and not the stack?
I don't get why we need to do this. Why not just work with variables?
You should call this video "2 - Pointers and Dynamic Memory in C++ (Memory Management)" continuation of "1 - Call Stack, Scope & Lifetime of Variables"
At 4:36 I am confused you said that you were dereferencing the pointer p when you were changing its value. Does the asterisk mean "dereference", I thought to "dereferencing" was only when you were getting the value of whats being pointed at, not reassigning its value. I'm not trying to be difficult I just don't know.
Why does 'delete' not actually delete p?
Like the entire variable?
Otherwise, isn't the memory for that int still wasted?
so can I write
int *p = new int;
*p=5;
p = NULL;
and skip ( delete p ; ) line like that ?
So if int* p = new int; creates a pointer on the stack and space for an int on the heap, does the following allocate an int on the stack instead?
int x = 5;
int* p = &x;
Or is x still created on the heap?
+Lambda x is on the stack in your example, assuming it is being declared inside a function. If declared globally (outside a function) it would be in what the video calls the "static" area.
Stack memory is only guaranteed to be valid for the life of the function so pointers to stack memory should not be returned from the function.
+lockbert99 Cheers, thanks for clarifying that for me.
thanks friend greetings from Colombia :-)
Thank you for explaining it so well!!!
Thank you. I understood everything you said.
Hi :) thank you for such a wonderful lesson.
Just a quick question: is there a to get *p to point back to memory address 500? Like say for instance we point to 500 (after we allocated space at address 500) and then we point to 700 ((after we allocated space at address 700). Can pointer p point back to 500?