Boolean Logic & Logic Gates: Crash Course Computer Science #3 

*CORRECTION* AT 1:27 the graph says "Quinary System" but then the graph shows 10 possible states - which is actually decimal. Technically, there should be only 5 possible values there, but the overall concept is still the same. NOTE: Since we can't use annotations in our videos going forward if we find any smallish errors in our videos like this we'll leave clarifications in the episode description. Thanks all for the wonderful feedback! -brandon

I am a third year majoring in computer engineering and this video explains transistors and logic gates better than a semester class.

Bit at the end made me wonder if I'm merely a computer. Great episode! -John

Unlike most CS introductions, Crash Course does a great job in giving the student context, explaining how computers function at a fundamental level before applying layers of abstraction. Very well done -- As a Sophomore ComputerSci major, I'm excited to see more enriching content every week(:

Oh my god, THANK YOU for clearly explaining how each logic gate is physically represented in an electrical circuit. A lot of that abstraction makes it really daunting and hard for dummies like me to get it through our thick heads.

Just wanted to say I love the themed animations for this series. The computer UI, old Mac OS UI, etc. Always great work to the animators and team.

A good video as always! As a CS major myself, this is actually finally a series where I can answer questions and stuff in the comment section! Just a pedantic note for people who want a little more info: 1) There are also not versions of all the gates. AND, OR, and XOR become NAND, NOR, XNOR, respectively. They are represented by adding a small circle to the end of the gate. While they can be formed just by adding a not gate at the end of the inputs, they are common enough that they get their own specialized parts. You often here people verbally NAND and XNOR when talking about logic, so I think it is interesting to note even though this isn't computer engineering. 2) While by convention in truth tables 1 is true and 0 is false, this is often not the case when we actually look at real components. Because of power usage, the opposite is often used. Generally, the more common output is set to 0. 3) 0 doesn't actually mean nothing is flowing through. For example, we may set our 1 to 5 volts, and our 0 to 2.3 volts. This allows for us to have an "off" state at 0 volts. We wouldn't want our computer to be calculating stuff with 0s when it is off! There are also other uses for this state, but this may be covered in a future video.

She is a VERY good teacher. How she breaks it down so you understand the details and then subtly tells you about application of abstraction helps you focus on whats important... she makes actual little building blocks for you as she speaks.

My first real exposure and application of logic gates was in Minecraft with Redstone

Just passing by to say that I'm loving her course and excellent diction.

I used to make cpus in minecraft, and it's amazing what it could teach about computers. It makes you feel like you understand exactly how computers work, and in a sense, you do. programming using only 1s and 0s, creating all of the logic gates/decoders etc from scratch, optimizing, and attempting to add a second core. I've moved on from Minecraft since then, but it's a great tool to make use of if you have the game and want to go deeper into boolean logic/logic gates and computer architecture. The hardest part is creating an Instruction set that is powerful enough to let you program basic programs but easy enough to decode to keep you from ripping your hair out. generally, It would be a non-pipelined CPU running at about 0.7 hz, but some made optimised pipelines that allowed speed of up to 2.5 hz, which is amazing given that every transistor take 0.1 seconds to switch, and after a certain range, you must add a repeater, which re-strengthens the signal, which also takes 0.1 seconds.

As an Electrical Engineering Student who was always curious about how Boolean Gates worked, my life is now complete...

I was wondering where I'd heard Boolean before, then realized that I took a logic class last semester. :D

Wow! I love these videos. It's amazing how far we've come with computers.

I'm so happy this channel exists. Thank goodness it does.

Loving the casual reference to "Journey" aroud 0:50. Such a great game!

The circuit explanations would always go over my head when I learned it in class and I just skipped over to doing the gate symbols for everything. But I think it FINALLY clicked when I watched the circuit diagrams in this episode. Really nicely animated!

Physical basis of logic gates wonderfully explained!

Man I used to study CS a few years ago, love how you can learn all I learned in months in a few minutes. Great job !

I mean the fact that George Boole came up with Boolean Logic a century before it became a vital component of designing computers is pretty incredible. It just goes to show how the discipline of pure mathematics, that is studying mathematics not for a practical purpose that is known at the time, but just for the sake of expanding the scope of maths itself, can really pay dividends when the technology catches up with it.

I have took electronic design in highschool, in college and in university as ee engineer but this explanation would be so easy to understand at the begining. Great job as always cheers.

The sound effects accompanying the currents/ON/OFF/logic table animations make me so happy :)

That feeling when you literally have a test on this tomorrow

This is really amazing, you have answered so many of my questions in this series so far and I am excited to see more videos in the future!!

I'm so glad you're making this series, this will help more people understand the concepts and fundamentals behind computers and computer science :) I'm dual majoring electrical engineering and computer engineering and while I already know all of this content from my courses, this series is absolutely fantastic and I wish I had it when I was going through my early classes. This is something I could definitely see good professors showing in their classrooms before getting into the nitty-gritty math

Carrie Anne is effortless and brilliant. She made logic gates delightful. More please.

Minecraft redstone already taught me this

As a CS grad that graduated over 5 years ago, this video had me giggling and remembering many classes, thanks!

I cannot believe I have learned NOT, XOR, OR gates and all other jargons in just few minutes. Please keep making more videos on computer science. How about videos on programming languages, electronics and mechanism? Your brilliant videos make our small brains balloon up.

I HAVE BEEN TRYING TO FIND A VIDEO THAT EXPLAINS THIS CONCEPT IN A SIMPLISTIC MANNER AND YOU ARE FINALLY THE VIDEO THAT DID IT FOR ME!! THANK YOU SO MUCH!!!

loving the series! wish i'd have had this to watch before starting to study computer science :D (i just finished the first semester) you're doing a great job at breaking the subject matter down and making it interesting! i'll be forwarding this series to anyone asking me what i really learn about!

I truly love this series. and really all of the programs here on Crash Course. The re-enforcement provided here is amazing.

Carrie Anne is the best. So good at explaining these concepts clearly and with a little humour thrown in as well.

I am in love with this series, I think I should set a date to watch this series every Year !!!! It is super refreshing to see and realize how it all started and obviously unravel all the levels of ABSTRACTION :)

The feeling when you don't have any exams tomorrow, but are doing it for fun and now the whole new world of Computer Science has opened for you to learn and become a master of every computer you'll ever meet in your life.

I appreciate that this video relates it to actual transistors and not just starting with the arbitrary principles/symbols. Relating it to the real world is important.

You are amazing. I have always been fearful of this information. I see now i was fearful of the instructors. Where you are concise, cheerful and fun they were scattered, drool and resentful. Thank you for knowledge!

Two and a half years into electrical engineering and now in this video i learn these stuff. Really well done!

omg love the Journey reference!!

I've been 40 years in the industry, and I learned to program (in assembler) from a PDP8 manual back in 1967. Congratulations on making a complex subject very approachable. Curiously the good old 6800 microprocessor had a "half carry" in the status register, and the DAA instruction specifically so that it could work with two decimal digits to a byte (BCD). If you were using it to implement something like a cash register it was easier to work in decimal than convert to binary and convert back.

It would have been really neat if you had gone a little deeper and talked about the NAND or NOR and they are functionally complete on their own can build up to any of the other logic gates.

I absolutely love this course, and would like to thank you guys for one extra feature that most channels don't care for: subtitles!!

Boolean logic came from a professor at my university, University College Cork (UCC) in Ireland. His name was George Boole. He's very famous here. Our main lecture theatres as named after him. Along with are library. Funny fact about him is that he died after getting a cold because one day when it was raining he forget his coat. Anyway I hope this piece of info helps in your studies of Boolean logic.

Thanks Carrie Anne, I'm really looking forward to the rest of the series!

Minecraft Redstone is just like real life.

She has gotten much better compared to the first 2 episodes. Keep it up Carrie Anne!

"Try turning it off and back on again" Great sign-off. :)

This is the best course i've seen. I've learned so much in 10 minutes, thanks for the explanation!

Not wearing pants means something very different in England

These series needs more views. Too few people nowadays know basics of how computer works.

Journey!!! Awesome reference!

I'm in love with this series. Hat off to Ms. Carrie Anne, her explanations and engaging methods are superb.

Very useful for those who love redstone.

I never would have guessed how useful my intro to logic class is when it comes to this aspect of CS. I'm so glad I took that class.

That Journey shout out.

The way you're organizing this series is pretty clever

Brilliantly explained! I am really hoping you will talk about more theory like Turning Machines and finite automata

I already knew at a basic level how AND and OR gates worked but I never realized before watching this video that the difference between the two is basically transistors in series vs parallel. That is super easy to remember.

Neat pickup line: "If I were to ask you to go out with me, would the answer to that question be the as the answer to this one?" XOR gated!

I'm in love with the comprehensive, engaging and enjoyably simple content being put up here!

This is SO GOOD!

I'm currently in my first year as a software developer apprentice and we do learn many of these things in school, for example logic gates. But this series is so damn helpful for me since we never really discussed the origin of it all, or why exactly we need these gates. knowing what role a specific topic plays in the field you work in and its physical basis makes it so much more interesting. thank you so much for the work you put into these videos!

That was both the longest and shortest 10 minutes of my life :'O

Great summary of some basics on logic gates. I am amazed by the speed of Carrie Anne's reading and diction.

My former university held a festival dedicated to Boole, I now know why!

I'm so happy you guys have started making this series, as a first year computer science student, it's helping a lot in the bits that I didn't quite understand in lectures. Thanks guys, and keep up the great work!

Carrie Ann is beautiful! Although I consider myself a veteran of this material, nonetheless my attention is captured and I find the journey up through these layers of abstraction from the flowing of electrons to the touch pad interface I am using at this very moment quite refreshing.

I've been struggling with the diagrams at the end for like 2 weeks now so thank you for explaining them simply, I might just show this to my professor

"a robot dog must always bark at a squirrel, as long as it does not conflict with laws 1 and 2"

This is just what I needed! Loving these series.

"In computers, an 'on' state, when electricity is flowing, represents true..." IMO this is at best misleading; in practice, it might be the other way around, but much more usually *voltages* represent states, and so bits, not currents. But many electrical and optical representations of bits are used in computers

I'm currently doing a coding bootcamp and studied a whole section of boolean logic. I felt like I understood pretty well but I also felt like I was missing something. Watching this filled in some of those blanks and made the whole this make so much more sense.

0:50 Nice Journey reference!

Thanks Carrie Ann for doing this. Never had a computer science course. And this stuff is great.

THE LOGICIAN I leave you with this conundrum - Boole me this, Fatman: "I am a liar. Everything I say is a lie. I'm lying." Compose a coherent logic gate output using that set of input statements before the auto-destruct countdown goes from 30 seconds to zero and both you and the Boy Dunder are... deleted from existence! LOLOLOLOLOL!!!!!! [exits with henchmen AND, NOT, OR and XOR as the countdown begins]

I loved it. Short, precise and full of information. I didn't waste a second. Keep it up.

The quinary system doesn't seem rightly represented, I mean in that system the only numbers posible (using our current Indo-Arabic numerals) would be 0, 1, 2, 3, 4 (or 1, 2, 3, 4, 5). Yet the graphic at minute 1:25 uses all Indo-Arabic numerals which would mean is actually decimal and definitely not base-5!

Have studied computing for 4 years and never seen how logic gates are physically made with transistors, really awesome video!

first few seconds i was like " -__- " and then i was "

WOW, the flow of this series is extremely logical!

that journey easter egg tho

A natural teacher. It's reminding me of a few semesters back.

5:10 I thought you were brave for going commando, but no pants or trousers? I guess that's why we can only see you from the waist up?

This was exactly the type of course that i was hoping for in this series. Well done!

trust me, you're not early. message from the past future.

As much as I hate the complexity of these videos, I love how much I'm able to learn from them. And I believe I'm speaking for thousands.

What about NOR, NAND and XNOR?

Thanks for explaining this to me. Got a test tomorrow and this is part of it. Anyone wanting to be an aircraft mechanic, take heed. This is part of the curriculum.

Your “and fortunately” sounds like unfortunately!

wow, this video is pure gold! you just perfectly explained the transistor much better than my electro technology teacher who teached the subject for weeks but failed to explain it, and not only that, you also showed other gates :) i love you, thank you so much! Now I finally understand it. :)

NOR gate? :(

Holy hell, I’m so happy i found a resource this detailed

My brain hurts

This is the best thing I've seen in a while. Thanks!

first() || !first(); I win.

This is my favourite crash course subject thus far!

Is that dress blue?

Carrie is such an amazing person. I wish she narrated half the stuff I find on youtube.

when they say "if you're in England" and use the union jack, like the english flag is the St George's cross :(

This channel is awesome. Where have you guys been all this time? I love it. After the first episode I am addicted to this channel. Well done.