Checksum
ฝัง
- เผยแพร่เมื่อ 6 ก.ย. 2024
- Checksum is a method of checking for errors in a communications system.
I'm Mr. Woo and my channel is all about learning - I love doing it, and I love helping others to do it too. I guess that's why I became a teacher! I hope you get something out of these videos - I upload almost every weekday, so subscribe to find out when there's something new!
For categorised playlists: www.misterwootu...
Main channel: / misterwootube
Discussion: / misterwootube
Worksheets and other resources: woo.jamesruse.n...
Man, your presentation/teaching skills are spotless. I'll be watching your videos before my next presentation. Thanks
Sir, you are the kind of teacher that doesn't induce the students to sleep. And there's only a few instructors that have this talent.
couldn't be more clearer.......that was very helpful.....hands down you are a good teacher
Great charisma. I think you will do well as a professor or a owner of a gigantic cram school chain. I hope you will post more educational videos like this and your TH-cam channel will flourish.
this is the top google video search result now for checksum! nice work. I was surprised to see a Ruse logo to the side. Recogised the AHS and gesta non verba lol! which year did you join/start teaching? which subject do you teach? i dont remember learning checksum even in SDD
haha.. Im also asking the same question to myself about the subject he teaches. I think he is a mathematician. Most of his videos are math. But I would like to see more computer videos like this.. I know there are lots of video tutorials on youtube but I really find his teaching interesting and it really sticks with my brain xD
Hahah, funny.
Today this guy is rocking
You're damn right about that :)
Quite a famous person now :).
Most fabulous and enthusiastic CS lecturer ever. Love it!
Great video, but I really really hope that that "keyboard master race" dude in the background STOPS !
XD
hahahaha
😅😂
Lmao 😂
This is one implementation of Checksum however it is abstracted a bit much to make it easier on the students, hindering its purpose.
It's usually done with the sum between all words in the msg like in the video, but the final value is given its one's complement and appended to the message.
If the transmission is correct, repeating the procedure on the other end (except now with the appended checksum) will result in FFFF assuming 16 bit words. No division operation needs to takes place.
Knowledgeable, clear, enthusiastic and dynamic. Great teacher.
watching after 8 years of uploading, and I am finally satisfied here. -29 April 2021
WOW. Thank you Eddie. Literally three months of confusion cleared up in 6 minutes.... Thanks again
Cramming for my last final at uni, thanks for helping me with Computer Networking Mr.Woo :)
I hate to be "that guy" but that is not how checksum works. It works at bit level, but for argument sake, if you wanted to give a decimal example, it is still not analogous to how checksum works. Neither side computes the remainder, they just sum. The trick is both sides know the sum, let's say for this example it is 100. The sender adds everything and the checksum is whatever number you need to complete 100 (in your example because the total is 72 your checksum would be 28). The receiver just adds everything and if its equal to 100 it is correct. The checksum can be placed anywhere in the sequence (beginning, middle or end), again, because it is only adding, or checking by sum. This is important because it is usually placed at the end of a header (between the information about the data and the data itself). Even my example is still not exactly how it works, but it is a good decimal value explanation/simplification. If you use a cyclic decimal value definition (say values from 0 to 31 and 31 + 1 = 0, sum of values = 31), you can get a more accurate depiction, but at that point it is just easier to use binary values.
What we have learned in Cambridge O levels is that we have to divide that sum "X" by 256 take the answer in whole number , Y. Then Z=Y*256. Then calculate the difference (X-Z). This value is checksum.
example:
X=11855
1. 1185/256 = 4.629
2. nearest whole number = 4
3. multiplying by 256 gives Z= Y*256=1024
4.The difference (X-Z) gives the check sum: (1185-1024)=161
5. this gives the check sum= 161
BTW I really love your lectures. :)
I think you made a mistake in line 4
Very Good Night Engineer ... One question ... You can take Checksum to a KM of a Suzuki Vehicle
This gentleman is a wonderful teacher
No clue what this is about, clicked randomly but kept watching because I was so drawn by how good your presentation skills are
This is amazing, I've learned so much in under 10 minuets what my professor was trying (and failing) to teach in an hour!! thanks a lot
Mr. Woo, Please upload more videos like this. Really simple and easy to understand your teaching. I like it
I can see why Eddie Woo is one the best teachers in Australia!
eddie would really apreciate u coming over to greenford high school and teaching it wouldbe great
Nice video, thanks for the help. The remainder for the second example is 9 (opposed to 7).
Hi Eddie, very much impressed the way you explained checksum . On databases also there is checksum not able to understand by reading . If you have anything on that can you please upload . Thanks
You have a great enthusiastic characteristic personality and you have a cool accent :p. Your video rocks.
Great video, clear and easy to follow. First time I've walked away feeling good after trying to get my head around this principle.
I just subbed because of an interesting random math video, but I would have never thought that you would actually help me with stuff I needed. Thanks for the awesome video! I never understood checksum before it.
Great vid thanks! One question though: Where is advantage of using a devider instead of just comparing the sum?
If the sum exceeds 26, you cannot put it in the message.
@@aronquemarr7434 I had the same question, so thank you!
Great video and glad I found your channel. Obvious passion with great teaching talent.
Very well said Mr. Woo. I love your presentation style.
great explanation , and i am vary glad to have a Eddie Woo in this profession u deserve that position,and i think i have to copy some teaching techniques from you .. any way thanks a lot..
😂
Man you're explanation is sooo clean ! Thanks
Best teacher ever.
Hi Eddie.. Its really a nice video. But I have question for you. You have a data 25 11 12 13 .. initially which gives you checksum value 8. and when you changed the data to 24 12 12 13.. also gives you the same value 8. This lies under the error but still it passes the checksum value. In such case how can we ensure the data integrity?
great vid! but how do both computers know what number is the divisor??????? like in parity the check digit is based on the numbers added together, but here it depends on the divisor which can be anything!!!!!!!!!!!!!
So is there any way to get around the balanced offsets on your data (when you changed 23 to 24 and 11 to 12, resulting in the same checksum?) Seems like the size of the divisor wouldn't even matter here. Perhaps it is so unlikely that it's not a significant problem? Or is there a secondary check that is not a checksum that can detect this? If anyone knows, I'd appreciate the knowledge.
Dude ur so good at teaching.
Wow, this is awesome. You explained that really well. Was mesmerised by the whiteboard! Wish my Uni had them
I remembered my classroom in like first grade had one of those. I've never really looked into it too much and as far as i can remember, this is the first time i've ever seen one since then. I didn't go to second grade at the same school since i moved.
Very clear explanation. Thanks.
Loved the way you teach :) Thank you for such a spirit :D
I absolutely agree ^^ pretty cool :)
where to watch the full Video/lecture/lesson?? the links in the description are infected and not working?
Great explanation ! You really make things easy to understand. Thank you
Can you plz give example of hexadecimal checksum?Does division hold good for hexadecimal too?
You sir are an excellent teacher. Thank you very much.
where have your videos been my whole life (aka these past 8 weeks in my networking class lol)
Is this operation the same thing as a modular checksum? Thanks.
Thanks you very much from Uruguay, you really help me a lot with this video.
Great videos, taught so clearly and with great atmosphere.
very good presentation of the concept. Really i liked it.
what if sum of bits and checksum changes in accordance, for eg if sum changes to 88 and checksum also changes to 9, then would that message will be flagged as incorrect ?
We use checksum in computer science all the time, it is an important piece in knowing if credit cards are valid for example.
Thanks for the video. Is that Fletcher's checksum?
wow , this is a real top of the class teacher , never saw one of those in my life really interesting
Why in checksums are you looking for the largest multiple of 16? Is that just a rule? That you need to look for the largest multiple of the agreed on number?
This has helped me a lot but what would the question be if it came up in an exam?
Josh Wood design a hamming code an complete a parity check. identify any flaws in check method
exact words off my exam
Thanks for uploading this video, really helped me out. You make an awesome teacher btw =)
Fantastic explanation! I feel I'm finally starting to get a handle on the concept.
Thank you it help a lot to understande how checksum works...i appreciate so much.
Very nicely explained-
Thank you so much Eddie, this and the parity check video was so helpful.
If the checksums match, the data was almost certainly not altered. So, why does the checksum or CRC by itself not provide security?
I love your energy.
Wohoooo your vids helped our class alot thanks heaps mista woooohooooo!
Thank for your explanation!
anayone can explain me how can the 15 is the largest checksum? how can the same sum of the number send while they are different is detected?
Man, I wish you were my teacher in college!
I'm confused. I learned checksum to add al the numbers then flip the bits (add one depending if I'm using ones or two complementary addition.) then you add that the end of the message. The reserver adds it up and should get 0 if right.
This looks like a mix of checksum (the one I learned) and CRC. So I'm confused.
+cook7772 I think the ones complement and two's complement thing is exclusively for dealing with negative numbers, while checksum's main goal is to provide data integrity.
good teacher i like your teaching skills
dude, that was great.....ez.... no bs. clear. have an upvote.
a larger divisor means that the sum of the message can have more possible remainders. only one remainder can be correct. so more remainders means more chances the checksum could be wrong. which means less chance it can be right. so the larger divider the more secure the check is?
you explained well...!
Thank you for such great channel
Wow, superb teaching..!
Thank you so much , It helps me a lot to understand checksum in NW ,
Keep going :)
Explained it well. ❤
YOUR SAVING LIVES OMW !!!
Love the use of the smartboard
very well explained video
i became a great fan to you eddie..
i love u. clear and easy to the spot
love your videos so helpful but how is the divisor chosen
Great work man... Thanks a ton... This surely helped...
Best teacher
you teach awesome !
Great intro!
you are awesomeee! such clear explanation that I wish you're my lecturer xD
The model of whiteboard is giving me nostalgia.
Amazing.
Why is a bigger divisor preffered when the chances of the data being sent wrong are more? Please help me Eddy Woo
Really Good, thanksEddie
I like the way you explain .. I got it right a way ..
BIG like + subscribe ..
I can't wait to watch the rest of your videos .. keep it up
Thank you very much Eddie!
like your way of teaching....
How can the remainder be 8, when 72 (sun) : 16 (checksum) = 4.5 and not 8?
i was wondering will 16 be given in the question?
sir why you not uploading full video's why ?
awesome!! u made me understand the checksum, ty kind sir
Um, very helpful man, keep doing this!!
What is the student saying around 5:18?
4:55 that kid who is typing in background is definitely playing fortnite lol he grinding with his 10000 dollar pc at school lol 😂
Thank you professor Woo!
And as we discuss parity / checksums I cannot help but notice this is uploaded to a "eddie woo" channel.... but the professor appears to be one James Ruse -> huh.
So thanks to both of you or one of you with an alias... or something.
@@inadaizz Where do you find he's Professor James Ruse? He did teach at James Ruse Agricultural High School per Wikipedia. Also this might provide more insight. th-cam.com/video/30j8e7PZXgI/w-d-xo.html
Well observed.
thanks alot but i wonder if you can introduuce more examples
That whiteboard setup is sliccccckkkkkk