Pointers in C

[@TheSar]

I studied C native in University on Solaris and this explanation of pointers is far and away better. Better on all fronts. Well done Sir.

[@skilz8098]

This is just the basics, here he is only addressing it... wait until you work with dynamic memory and the heap... I've learned C long ago but I'm more familiar with C++. The basic way to create a block of memory in C++ is with new and new[] and to free them is with delete and delete [] respectively. Today, this is considered bad practice unless you truly know what you are doing and you have a very specific reason for using "raw pointers" as the conventional way is to use std::shared_ptr and std::unique_ptr... In C this is done with malloc() and free() and some other memory-based functions.

[@Seaprimate]

I feel that despite not having any fancy visuals or elaborate analogies, I feel I intuitively understood more in these 10mins with your video than I did through multiple other longer videos combined. I don't know how you did it but thank you!

[@liamhulsey9158]

Currently in a college course learning C and this is the only explanation I've heard in class or on the internet that makes pointers make sense. Can't thank you enough.

[@GaryExplains]

My pleasure. I hope your courses go well 👍

[@john_avernia]

I just started learning programming (several weeks now) and your video really helps me a lot in understanding pointers. Which is, from what I heard, is one of the hardest subject in C programming.

[@Hunter725R]

Me: Visual Studio for C with autocompletion for smallbrain Him, a divine being: nano on a Rasperry Pi Zero for C.

[@SwedishDude08]

@Christian Weissmuller Vim is evil, use emacs instead and enjoy your sprained pinky!

[@dgaa1991]

@@SwedishDude08 Well Evil Emacs is kinda nice :D

[@volkerking5932]

@Christian Weissmuller vim is for noobs use xemacs!

[@Andrew-wo8ry]

Notepad++ gang.

[@ihitonmilfs]

you guys still use nano? real men just echo "#include int main(){printf("Hello World");}" >> program.c

[@LoyalSlime]

sir please do more C tutorials

[@GaryExplains]

If there is enough interest then I will.

[@thomasb1337]

I'd love it. I'd even pay for it on something like udemy =.

[@josh429]

+1

[@stephenjames5745]

That would be amazing!

[@nikhil.n]

sir we are interested in programming tutorials do make more of them.

[@fifaham]

I have been browsing for tutorials and found many on KZbin for things I already know, I found yours to be one of the best and I will keep your link here with me. Job well done.

[@skylo706]

Oh I wanted to make a tutorial on pointers myself called "How to SegFault in C"

[@qwerasdfhjkio]

Lol

[@SwedishDude08]

To people getting this error message from gcc: warning: format ‘%x’ expects argument of type ‘unsigned int’, but argument 2 has type ‘int *’ Change %x to %p and it will work.

[@davidmella1174]

yes, some things have changed with the new C standards in the compiler.

[@boazvoort6869]

"%d" worked for me

[@abrahamnzau254]

By far the best explanation of pointers I have come across

[@Ejeby]

4:30 & tells you the address, * tells you the dereferenced value 6:50 in c an array name is equivalent to its pointer 7:30 increment the pointer

[@JJSogaard]

I'm just in the beginning of getting into C after learning Python. There really is something beautiful about how basic and (relatively) low-level it is.

[@DrSpooglemon]

Scared the b'jesus out of me moving from the well ordered metropolis of Python to the wild west of C.

[@MrGman590]

Now I understand how pointers work, after 4 years of trying. Thanks for explaining, Gary!

[@D3ND]

Great video! pointers are definitely one of the more tricky parts of C that I have faced, especially when going for data structures (linked lists, dynamic arrays... ) with allocating and freeing and so on...

[@brokenicry]

I went through so many tutorials just to understand this...Only this single fast-paced video helped me understand... Thank you. Please tell me there are more videos like this

[@ShadowPianoProductions]

Dude, you're a godsend, I could not understand pointers for the life of me before watching this video

[@felaflame]

Excellent explanation. Simple, going straight to the point.

[@mukukakondowe5939]

Thank you for demystifying pointers for me. They have been a real pain in my neck.

[@ST95953]

my teacher couldn't explain this properly. Thanks!

[@easymatrixyt326]

Lol

[@cy4n_knight_q8]

Your teacher tried to explain this? Mine didnt even bother to explain lol

[@froggyy]

Change your college

[@CodyHoskin]

Haha same

[@johndripper]

Read books😔🙏🙄its not even a hard concept to grasp

[@陈瀚龙]

Old guy here. I've been self-teaching Java and soon to start Android, but not sure how to approach learning Android. I decided to take a break and learn some C and explore Linux more in-depth which led me to this video. It was nice to see you using NANO and excited to hear about the Java/Android course. I'll have a look. Great job with this vid, short as it was, good introduction to pointers.

[@eatscaper]

Your tutorial in C was superb ! Make more tutorials and gain the attraction of new developers and of course you are great !

[@woomlrweiriwueiru]

Best pointers explanation I've seen!

[@cookymonstr7918]

It dawned on me as you were typing (3:11) *aptr = &x because in a variable "aptr" you literally store the (hex)value of the address of an "x", which is nothing else than &x. No more, no less. The only thing that confuses me a bit is that doing "pointer arithmetics" decimal number is added to hexadecimal...

[@GaryExplains]

Decimal and hexadecimal are just ways we represent numbers for humans. The numbers are the same. Adding 15 to something and adding 0xF are the same thing.

[@JesusMartinez-zu3xl]

You literally taught me in 12 minutes! compared to what my professor taught us... Thank you!! also understood you much more better.

[@arjunkharbanda]

One of the best video on pointers. Please make more such programming videos like Data Structures etc

[@aliftaufik1934]

The question is why should we prefer using pointer rather than using, for instance, the index number of array to loop it??

[@danielgysi5729]

This is what I hoped this video would explain. Unfortunately I'm left feeling more confused than when I began

[@SamChaneyProductions]

Pointers allow you to change the value of multiple variables from inside a function, and they even allow you to pass functions as arguments into other functions, both of which are impossible without them.

[@RadicalEagle]

@@SamChaneyProductions thank you! As someone who is not familiar with C I couldn't quite understand why this was important.

[@reiniertl]

There is a very interesting advantage but I really don't recommend it unless you really need the most performance. When you use array indexing in a loop the compiler (in theory) generates code to bring into the CPU registers the base address of the array and the value of the index, then it must compute the address you want to get access to. So you need two read access and a sum (all this is in machine code so it is very architecture dependent). When you use a pointer to access the elements of the array and you are traversing the array in a fixed pattern you can take advantage of pointer arithmetic, since you are incrementing the address by a fixed number the compiler generates code to bring the address value to the CPU register and the increment will be put into the ADD instruction code, so you save at least one instruction per access (no need to fetch the index value from memory). For example, the code bellow shows the differences: #include int array[10]={100, 200, 300, 400, 500, 600, 700, 800, 900, 1000}; int main(){ //This is a bit slower but more clear int val; for (int i = 0; i

[@jvarennes]

Better to use pointer when, for example, you don't know what the array size will be at the beginning. Let's take a text file which has to be parsed and values stored. First, you do a malloc which gives you a pointer and begin to read the text file. Then, if you haven't allocate enough memory, you can do a realloc and continue to read and parse the file.

[@MarcelN1980]

Thank you Sir, subscribed in 2021, all the very very best from Romania :)

[@pcache]

I didn't learn anything new about pointers, but boy oh boy I had no clue some shells supported the exclamation point notation for repeating previous commands, that makes me excited.

[@dwagner6]

Been a while since you shared this, but a better explanation than my professor at uni explaining c++ pointers. Cheers.

[@nayanarora4966]

Best explaination I have ever seen

[@NinjaRunningWild]

That sign behind you terrifies me, fully understanding what that will do. Happy debugging!

[@GaryExplains]

Why should that terrify you?

[@GaryExplains]

Here is a little C program using the code on the signpost! #include int main() { int **ptr; int *ptr2; int x=42; ptr = &ptr2; *ptr = &x; printf("x is %d ", **ptr); return 0; }

[@emilyboyle7240]

this is the best explanation ive come across so thank u for this. i am curious as to what the point of pointers are. to fill the array u also could have just referenced each index as well

[@GaryExplains]

If you had a large Image that you want to process in a function, should you pass the whole 5MB to the function or just a pointer? They are also useful for many types of data structures, see my video on linked lists.

[@StannyObelisk]

Gary mate you’re a legend

[@jourkevin5254]

missed that part at school because of the covid , had trouble with the array part. Thanks for the video. Aannd subscribed

[@akhilsreedhara968]

you have taught pointer better in 10 min than my professor has in 3 hours

[@nagesh007]

Thanks a lot , can you please teach " C structures and unions" ?

[@neelparekh1759]

It's easy 🙄🙄, I hope you have learned till now 🤣🤣

[@thsdsyt]

The star (*) is called the indirect operator because it access indirectly the value of a variable through the pointer.

[@JP-nj2sl]

Very clear explanation of pointers

[@eliasdetrois]

Great tutorial. Thanks

[@OMNI_INFINITY]

Is it possible to make the val of a non-pointer var a mem address and then use the * operator on that normal var to get the val in the mem address that is its val? There must be some way to do that, unless it was architected to not allow that (doubtful)

[@GaryExplains]

Why a non-pointer var? I don't see the need or benefit. As a side note, with casting you can convert almost anything. For example: #include void main() { int x = 42; long y = (long) &x; int *p = (int *) y; printf("%d ", *p); } Output: 42

[@OMNI_INFINITY]

@@GaryExplains Apologies that I didn't see that reply until today. Thanks for including that nice example code!👍🏻

[@FritsvanDoorn]

Your main function should return a value. Other declare it void. Good explanation! Very clear.

[@GaryExplains]

LOL, not the grammar police, but the code review police. 😂

[@DaSnipy]

Thank you so much Sir .. Such crystal clear explanation with demonstration.

[@yoelin9253]

This was so incredibly helpful! Thank you!

[@GaryExplains]

Glad it was helpful!

[@kc2838]

Sir, please do more videos on more C concepts.

[@ujvalmadhu5482]

Can someone explain the purpose of a pointer, because you can just directly increment the index of the array (somenumbers) to update its values right? Instead of using a pointer? Why not call the variable directly??

[@michaelshort2388]

Thank you for the informative video. Is there any benefit to using a pointer to traverse an array vs the traditional way?

[@Kakashiownsyou]

Big ups for Nano. Big ups for good display colors. Salutations, friend.

[@vishma9166]

Thank you very much Gary. Very helpful.

[@eren8227]

shouldn't printing the address of what pointer holds be with %p and proper type casting?

[@patrickdeniso]

Thank you! You explained pointers really well

[@Goodbirb]

I've always used vs code, but now um curious on how do you code in the terminal like that

[@michaeldausmann6736]

Great video Gary.

[@JM-yj4yy]

has pointer exam in 2 days, bless you KZbin algorithm, sweet child

[@1MarkKeller]

*GARY!!!* *Good Morning Professor!* Great video as always!

[@GaryExplains]

MARK!!!

[@DanielAlmeida499]

Great video! Thank you

[@barakyehudagortler6265]

tnx you explain in an interesting and clear way

[@KoKoKen]

commenting four years late but thanks dude this was massively helpful

[@GaryExplains]

You're welcome!

[@DavidBarnwell876tkdja]

I'm getting some strange output. I'm getting 5 outputs. The first gives the value 2, then, values of the other array elements (all 0) then the fifth value is the memory location of the last element. Then, it repeats with 2, hen, 4, then zeros, until it prints the memory address of the last location. This happens 5 times until the array has been completely filled. It's weird ..I can't see what could lead to that behaviour, Never mind..I had the second for loop enclosed inside the first..that was the problem. It's all good now.

[@Dish.Washer]

@7:49 Isn't saying somenumber[5] going out of the array?

[@xiajack1507]

the for loop terminayion condition is ptr

[@TheTestr]

The confusing part is that you use * to tell C that a variable is a pointer. But when you want to save something in this variable you use & to get an adress and * to get a value. I do not understand, why it is not the other way around..

[@fazp]

this video made sense for me and it gave me an idea what a pointer really is to my small brain 😂

[@radddish]

thanks gary that helped a lot !

[@CaptainWumbo]

it would be nice if you explained why you would want to use a pointer over access by index. Is it more efficient in some way? It looked to require a bit more knowledge to read. I never did anything with C before, so the only value I can intuit is that passing a pointer to a function can save copying the value in cases a copy doesn't help. It's not clear from the video why you would prefer to deref a pointer over using a variable directly.

[@GaryExplains]

Well, why you would use pointers is different to how. This video is how. Check out my video on linked lists for an example of why.

[@lihanou]

concise, straight to point, thanks

[@supergoofy123]

Thank you. We need more videos like this.

[@GaryExplains]

I will certainly do more programming videos including C and Python. However they aren't the most popular type of video, so I will only be able to do them from time to time.

[@dutoitvandyk2531]

well done, really well done. Can you please continue to teach C in such a understandable way.

[@GaryExplains]

I am glad you liked it. I will certainly do more C tutorials from time to time, but my only concern is that they don't seem that popular.

[@dutoitvandyk2531]

i can see that from the views, I feel like there is so little interest in C because it is quite a difficult language to learn, especially as a first language. Its my first language I am learning but only because it's a module i have too finish for my degree . I would personally like to learn python first, love the language and the simplicity. I have learned a lot in this video and used it to do one of my tutorials. I've spent about 3 days now trying to figure out how to assign new values to an array and keep the memory addresses. Then it needs to give the new values for the array and the addressees. Just can't seem to get it right..... The fact that the C videos are so unpopular might actually have to do with the fact that no-one is interested in learning it as a first language and because of the immense lack of useful videos on it, which is kind of a vicious cycle.

[@arunsc37]

Thank you this is 30x better than my prof

[@raphtlw]

Hey Gary, can you do a video on the difference between C and C++ and C#? Thanks for these awesome videos!

[@GaryExplains]

Hmmm, that could be an interesting video... thanks for the idea.

[@raphtlw]

@@GaryExplains ❤️❤️❤️❤️ I honestly can't believe you replied

[@nouramsaeed]

I really appreciate ur effort

[@GaryExplains]

Thank you so much 😀

[@suma4m]

3:00 Why does this: {int *aptr = &x;} and this: {int *aptr; aptr = &x;} give the same result? Why the asterisk can be placed both before variable name or after the type name?

[@GaryExplains]

{int *aptr = &x;} is a short form of {int *aptr; aptr = &x;} In the first the pointer is declared and initialized in one swift move. In the other the pointer is declared and then initialized in a second statement.

[@filker0]

As for why "int* ptr;" is the same as "int *ptr;", the space is not required by the language syntax. The type of the variable "ptr" is "int *", read as "pointer to integer".

[@canaDavid1]

One thing that frustrates me in c/c++ is how a pointer is made. Ie Char *ptr = &x; But as i have understood it, * dereferences the pointer. (And & tells us the adress of it). This code seems to suggest that in wherever ptr points, write address of x. But what it means is to write &x at ptr, no dereferencing. Therefore, I always write 'char* ptr' with the * before the space, to clarify this. Is this an oversight or am I just being silly? (My format is a problem if you are doing multiple variables: 'char* a,* b' should be 'char* a,b' in my opinion)

[@GaryExplains]

Yes, lots of people have the very same issue and they write the * to the left as you. For me it has never been as issue, because it only occurs when doing a variable declarations, so you just learn it for what it is.

[@canaDavid1]

@@GaryExplains Well that's a quick reply! Nice to know I am not the only one.

[@Jool4832]

Unrelated question: what's the name of the music you're playing for this video?

[@willd9807]

How did you get it to compile without return 0;

[@filker0]

There's so much more that can be covered with respect to pointers. Passing by reference, linked lists, dynamic allocation, struct pointers, function pointers, and using pointers with array syntax. Also, sizeof(ptr) vs sizeof(*ptr). Understanding pointers is essential to sophisticated C programming, and correct use of pointers is essential for robust and bug free code.

[@GaryExplains]

Yes, of course. This is an introduction video.

[@Abdulrahman-uk9ny]

Thanks a lot for the very good explanation. I am about to enter the final exam of C in college... I didn't understand the language well, but I may pass the exam... I think I need to study the C language again in detail.. please make a whole tutorial for C language.

[@volkerking5932]

Hello Gary one question about the first => for(;ptr < &somenumbers[5]; ptr++) I know that the pointer is at the start of this "for" on the correct point but where is this? you write => for(; - what is normal between the '(' and the ';' I make a attempt => for(ptr = &somenumbers; ptr < &somenumbers[5]; ptr++) {.... but my start condition follow by an error what is the correct start position of the pointer?

[@GaryExplains]

The first section is for initialisation. Your test was almost right, but should be "for(ptr=somenumbers;..." You don't need the & as an array is a pointer to itself. You could also do "for(ptr=&somenumbers[0];..."

[@volkerking5932]

​@@GaryExplains what I understand now = after making a error 'int somenumbers[5]; int *ptr = &somenumbers; - A array[5] is a hardware address itself! after initial a array[5] it is not need to say this is a addr in the RAM I only can say int *ptr = somenumbers; and this will accept it as a arrays first addr inside the RAM or where else. My pointers are xh,xl yh,yl and zh,zl over R0 :-) I only know how to program in assembler and this 'C' is only for lazybones - reason you never need to manage the vectors itself that is doing the compiler and not your brain. hahaha Super I learning again the 'C'! Thank you Gary! Best Regards Volker from vienna

[@GaryExplains]

@@volkerking5932 For arrays only, the array name without square brackets is always the address of element 0. So 'somenumbers' is the same as '&somenumbers[0]'

[@volkerking5932]

@@GaryExplains I see - wow that is a little bit complicated for me in the start sequence. I understand it I come from the assembler language but my story is harsh. I've be in the hospital in 2017 and my pancreas is died inside my body. The hospital send me for 61days to deep sleep comma and in sum it was 128days hospitalized. But that was hard and I loose all my knowledges/skills inside my brain so I must learn all again. I can't remember what I've done before my visit in the hospital? I learn now from 2017 September to calculate - yes I must learn mathematics and reading/writing that was also a bit hard for me to understand - ironical the assembler programming I don't forget but that I have had a wife and children that I can't remember. After this hospital they told me I've a family - I can't remember it. The people of my family was foreign for me and I can't live with the woman again so I leave her. She was a foreign person for me I can't remember nothing about us. No pictures and no feelings that was missed after this hospitalization. In case of the hard medication they gave me inside the intensive care I lost all data in brain from 2007 - 2017. I remember only things that far away in the time line. For example I remember back in the 80s very good and my learning time at Grundig (TV & Videorecorder Company). I must say thank you very much to you and I like this Video. Best Regards Volker from vienna thumbs up Nr. 4964

[@wedsonlopes2559]

please, do more classes like that!I am now subscribed.

[@viniciusleitecosta]

Greetings from Brazil!

[@grasshopperweb]

What about constant pointers? My text goes through them far too fast and I don't fully understand lines like int const * const pointer = &adr;

[@RushilKasetty]

When reading const, read from right to left instead of left to right. So, the pointer variable is a "constant pointer to a constant int". This means that after creating the pointer, you won't be able to change which object it points at, and you won't be able to modify the object it's currently pointing at. The first const (as in int const) means that the thing the pointer is pointing at can't be modified. The second const (as in const pointer) means you cannot change what object the pointer points to.

[@grasshopperweb]

@@RushilKasetty thank you very much! Clear explanation

[@galvanizeddreamer2051]

Finally, someone explaining what something is.

[@jadenlorenc2577]

Dang this guy does a really good job

[@johng7rwf419]

That took me back more than 30 years..

[@redrock9319]

Straight from 90's!

[@ProductionCowbell]

Very informative video 👌

[@jacobhansen3871]

Great explanation

[@GaryExplains]

Glad it was helpful!

[@JadedBeast]

Cool logo you have there , and thanks for making this video

[@davidpotesta]

I get a compilation error if I try printf("aptr is %x ",aptr); The compiler (correctly) tells me that aptr is a *int. To print the HEX address of what aptr points to I need to use the format specifier for a pointer which is %p and use this: printf("aptr is %p ",aptr); and it works. I guess my question is, why did your program compile with a format specifier that mine does not?

[@GaryExplains]

Yeah, my version is wrong. It depends on the compiler and the platform, I guess.

[@davidpotesta]

@@GaryExplains Thanks for the quick reply and for verifying that I wasn't crazy. Thanks for all of your great videos!

[@lukenukem8028]

Pretty cool. But, what is that primitive program you're using, and primitive OS? Is it like a DOS legacy inspired thing for certain people? I need to see my project structure, seriously, all files, etc.

[@GaryExplains]

I tell you what I am using at 1:42

[@lukenukem8028]

Oh, I def heard the pie and nano. Is the pie a computer, or OS on a computer, is it a console, terminal? Others use Sublime for C so I'm guessing Nano is something required for use on Raspberry Pie?

[@lukenukem8028]

I heard it, but it doesn't tell me anything. LoL

[@GaryExplains]

@@lukenukem8028 It seems you are missing some fundamentals here. I have videos covering just about every question you asked here. The comments section isn't the place for me to fill in the gaps for you.

[@lukenukem8028]

This is the first video of yours I've seen. I'm only asking what R.Pie and Nano are.

[@nousernamealexander]

I still can't explain pointers by myself. I still can't understand where I need to put a pointer when I am doing an exercice. Do you have some exercices to help me ?

[@throwitatthewall6289]

Understanding pointers was pretty easy from this. What I fail to see is why it is better than just referencing the variable.

[@GaryExplains]

If you had a 4MB image and you wanted to apply a filter, would you pass the 4MB variable to the filter function (which means allocating another 4MB and copying the image) and then return another 4MB (with allocation and copy). Or just pass the few bytes needed for the pointer?

[@manobrodeful]

Very well done, thank you very much.

[@mbunds]

Thank you Gary!

[@santosshresth4419]

love your contents here can u make a video explaining the digital ciruit realization of how pointer works?

[@ammaribrahim5756]

what assign addresses to memory locations such as bea54240? is it the bios?

[@GaryExplains]

It depends. If the pointer is a local variable then the compiler will get the address from either the heap or the stack. If malloc() is being used then the address comes from the OS.

[@ammaribrahim5756]

@@GaryExplains Thank you for your effort and your awesome videos... Mr.Gary......

[@yapayzeka]

behind you what is the type of pointer pointing :D

[@consciousness147]

brilliant! love how you made this video , thanks :)

[@c0ldw1nd27]

I already knew everything, but I still watched the whole video.

[@josh429]

Gary could you explain make and makefiles please?

[@GaryExplains]

That is a good idea... I will add it to my TODO list.

[@josh429]

thanks

[@dev-patel]

I cant initialize in the middle of code I have to initialize any variable at in start? how can you do ?

[@benediktbeck3987]

Really helpful, thank you Sir!