Speaker 1: Brought to you by the reinvented two thousand twelve Camray.
Speaker 1: It's ready. Are you get in touch with technology? With
Speaker 1: tech Stuff from how stuff works dot com. Hello everyone,
Speaker 1: welcome to tex Stuff. My name is Chris Pollette and
Speaker 1: I am an editor how stuff works dot Com, sitting
Speaker 1: across from me, as always his senior writer, Jonathan Strickland,
Speaker 1: logic clearly dictates that the needs of the many outweigh
Speaker 1: the needs of the few. Okay, so today we're going
Speaker 1: to plug Thank you. Today we're gonna talk about logic gates.
Speaker 1: But before we get started, let's let's let's begin with
Speaker 1: a little Facebook feedback you. This comes from James and
Speaker 1: James's suggestion Electronics one oh one logic gates. Thanks James,
Speaker 1: it was an easy one. Yes, we're going to tackle that,
Speaker 1: but before we do, I have a little listener mail.
Speaker 1: This listener mail comes from Chris and not the Chris
Speaker 1: who's sitting across from me. Chris says, you say in
Speaker 1: your three hundred episode that machine code can't be easily
Speaker 1: read by humans. That got me thinking humans made machines.
Speaker 1: I understand that the best concept at the time was
Speaker 1: to code computers and machines with this complicated and unreadable language.
Speaker 1: But in this day and age, why don't we build
Speaker 1: computers and machines that can understand our language. It just
Speaker 1: seems to me that some kind of cycle humans build
Speaker 1: machines that only understand a complicated language, we adapt to
Speaker 1: that language, and we build programs that translate a simpler
Speaker 1: language to the machine language. Is it possible for computers
Speaker 1: and machines to be built to process information in the
Speaker 1: languages we are accustomed to? Now these two items are
Speaker 1: actually related to one another. You might think, well, one
Speaker 1: of these we're talking about natural language, and the other
Speaker 1: one we're talking about logic gates. How do those end
Speaker 1: up being related? Well, it's because machine code is based
Speaker 1: upon the binary system zeros and ones and logics are
Speaker 1: as well. And it turns out that the way we've
Speaker 1: built computers is based upon this binary system, and that's
Speaker 1: why we have machine code. It's this two humans. It's
Speaker 1: a it's a complex way of trying to get a
Speaker 1: machine to do a relatively simple task, or at least
Speaker 1: one that seems simple to us. And unfortunately, there is
Speaker 1: not an easy way to translate natural human language into
Speaker 1: machine code in order to make a machine understand natural
Speaker 1: language in a on a fundamental level, like on a
Speaker 1: mechanical level, we would have to completely change the foundation
Speaker 1: of computing. Yeah, so that's why it's a big deal. Uh.
Speaker 1: You know. Instead, what we do is we end up
Speaker 1: building programs that can understand on on a superficial level
Speaker 1: what natural language is and translated into machine code so
Speaker 1: that a computer can respond the proper way. It's not
Speaker 1: true understanding, because again, a computer is just running processes.
Speaker 1: It's just running, uh, series of calculations using these zeros
Speaker 1: and ones and logic gates are the very foundation of that.
Speaker 1: It's the foundation of circuit treats, the foundation of electronics,
Speaker 1: and the foundation of computers. But it kind of goes
Speaker 1: back a long way back, in fact, before there were
Speaker 1: electronic computers. Oh yeah, I mean, because you know, I
Speaker 1: I think of it as, uh, well, we actually have
Speaker 1: an interesting article about it, um about something that has
Speaker 1: come up with a couple of centuries ago by a
Speaker 1: guy named George. Yeah you know. Oh yes, because logic
Speaker 1: gates operate using Boolean logic, we have then there is
Speaker 1: an article on how Boolean logic works, on how stuff
Speaker 1: works dot com, I recommend actually, which is basically about
Speaker 1: logic gates, which is kind of funny. I had no
Speaker 1: idea until I started doing research on it um because
Speaker 1: we also have a an article about how electronic gates
Speaker 1: work on the the the site. But there's they're sort
Speaker 1: of hand in hand. It's better probably to go back
Speaker 1: through the bully and logic article first and then go
Speaker 1: to the other um. But yeah, I mean, he basically
Speaker 1: figured out how to use uh, you know, I guess
Speaker 1: it's sort of the marriage of language and mathematical operation
Speaker 1: in some ways, wouldn't you say? Yeah? And I also
Speaker 1: tend to to relate it back to symbolic logic, which
Speaker 1: is another way of marrying mathematics with language. Now, if
Speaker 1: you're not familiar, symbolic logic is a concept where you
Speaker 1: reduce statements to sort of almost like an equation, and
Speaker 1: using the equation form, you evaluate that statement to determine
Speaker 1: whether or not the statement or the combination of statements
Speaker 1: is true or faulse um. And you know, you have
Speaker 1: to make some certain assumptions in order to do that,
Speaker 1: but you can build more and more complex equations using
Speaker 1: all these series of statements to determine if the ultimate
Speaker 1: conclusion is true or false, and by true or faulse,
Speaker 1: we're really talking about whether the argument holds water or not.
Speaker 1: So you can actually do this. You could take a
Speaker 1: debate and you could take one person's side of the debate,
Speaker 1: reduce it to this sort of mathematical equation, and then
Speaker 1: determine whether or not the ultimate outcome of that of
Speaker 1: that person's side of the debate makes sense from a
Speaker 1: logical standpoint. Yeah. Now again we're talking logic here. We're
Speaker 1: not talking about, uh, you know, trying to get someone
Speaker 1: to agree to something based upon its emotional weight, but
Speaker 1: simply does this argument makes sense? Does it follow the
Speaker 1: rules of logic? Yeah? And a lot of these UM
Speaker 1: when we talk about the logic gates UM, they're actually
Speaker 1: devices inside electronics that use these logical operators, these rules,
Speaker 1: these rules within the machine. Basically, they're passing instructions based
Speaker 1: on the type of circuit they are and according I
Speaker 1: actually look this up in Access Science, which is UM
Speaker 1: a really awesome database for for technical things like this. UM. Basically,
Speaker 1: the Access Science said that if you're creating a gate
Speaker 1: circuit UM, they could be made up of transistors, diodes,
Speaker 1: or resistors, in some combination. Now most today are are
Speaker 1: generally transistors only, but they could be made up a
Speaker 1: variety of components um and they're they're basically, you know,
Speaker 1: you hook these up, and you can hook them up
Speaker 1: in a variety of different ways depending on the type
Speaker 1: of device and what you're trying to get it to do.
Speaker 1: Um it. We'll get into that later, but basically, these
Speaker 1: circuits are um a series of components that are wired
Speaker 1: together to perform a logical operation within a device. So
Speaker 1: let's start off from the very very very basic steps.
Speaker 1: So it all begins with bits, zeros, and ones. Now
Speaker 1: this these aren't just numbers zero and one does not
Speaker 1: that doesn't that to us, That doesn't really mean anything
Speaker 1: other than the fact that we can do mathematical processes
Speaker 1: using them. As as as values zero and one um
Speaker 1: they actually translate into other concepts. So a zero in
Speaker 1: an electronics system would be a low voltage meaning zero volts,
Speaker 1: and a one is high voltage, meaning five volts. So
Speaker 1: a one means you've got electrons running through there at
Speaker 1: five vaults. Zero means there are no electrons running through
Speaker 1: zero vaults. But a zero also would mean a false statement.
Speaker 1: One means a true statement. Zero could also be thought
Speaker 1: of as being on in the off position. One is
Speaker 1: in the on position. So let's we have to do.
Speaker 1: You know, zero and one is kind of shorthand of saying.
Speaker 1: So if we're talking about zeros, we're talking about false,
Speaker 1: and we're talking about once, we're talking about true. For
Speaker 1: time about zero's we're talking about low voltage. If we're
Speaker 1: talking about one, we're talking about high voltage. This is
Speaker 1: how we translate ideas conceptually into a real device, a
Speaker 1: physical device that does something one there we go true.
Speaker 1: So now a logic gate will process a signal and
Speaker 1: what it does to that signal, like it has an
Speaker 1: input and an output, what it does to that signal
Speaker 1: when it comes in through the input is based upon
Speaker 1: two things. The nature of the logic gate, because there
Speaker 1: are several different basic types of logic gates, and the
Speaker 1: whether or not the input was true or false, so
Speaker 1: whether or not it was a one or a zero.
Speaker 1: Those two elements will determine what the output of that
Speaker 1: specific logic gate is. And the simplest logic gate is
Speaker 1: a not git that's also known as an inverter. Yes,
Speaker 1: Now inverters what they do is, they will take an
Speaker 1: input and switch it to the opposite output. So, in
Speaker 1: other words, if a zero is fed into a not gate,
Speaker 1: it will produce a one. So false statement comes into
Speaker 1: a not gate, it flips it to a true statement
Speaker 1: coming out right, all right, so or against low voltage
Speaker 1: to high voltage, yes, vice versa. So whatever the signal
Speaker 1: coming into the the not gate is, the opposite goes out.
Speaker 1: Now it can only have one input, which makes it
Speaker 1: unique among the gates. The other gates have two or
Speaker 1: more inputs, and they combine the two in order to
Speaker 1: produce a result. Alright, So then the next one would
Speaker 1: be an and gate. Now and gates will produce a
Speaker 1: true result only if both inputs coming into the gate
Speaker 1: are also true. I think of that like the programming
Speaker 1: statement if then if both are true, then it will
Speaker 1: return true results. So that means that let's say imagine
Speaker 1: that you have this. You can actually imagine that this
Speaker 1: is a gate and there are two roads leading into
Speaker 1: the gate, and you have two cars going up to
Speaker 1: the gate. If both cars are are true, then you've
Speaker 1: got a true result coming out. Otherwise you have a
Speaker 1: false result coming out. Actually, it would be and if
Speaker 1: and only if yes. So, in other words, if you
Speaker 1: have to If you have these two uh inputs coming
Speaker 1: into the and gate and both are a one, so
Speaker 1: both are true, both are high voltage, you get a
Speaker 1: one as a result. Any other combination you get a
Speaker 1: zero as a result a false statement or low voltage.
Speaker 1: Zero and one will equal zero. In this case, zero
Speaker 1: zero will be zero, zero one will be zero, one
Speaker 1: zero will be zero because you have to think of
Speaker 1: all three instances that way. Even though you might say, wait,
Speaker 1: zero one and one zero, isn't that the same thing? No,
Speaker 1: Because you're talking about two different inputs coming into a gate,
Speaker 1: and those two inputs are coming from two different sources.
Speaker 1: Sometimes yeah, sometimes they come from the same source, but
Speaker 1: usually they come from two different sources. And that means
Speaker 1: that because they're coming from two different sources, you have
Speaker 1: two different configurations. You have one where one is true
Speaker 1: and one is faults, and another one where one is
Speaker 1: faults and the other is true. Sounds kind of complicated,
Speaker 1: it's actually pretty simple. And again, if this starts to
Speaker 1: sound confusing, check out these articles that we have on
Speaker 1: our site because they will help illustrate these concepts. So,
Speaker 1: besides the end gate, you have the nand gate or
Speaker 1: not and now and not and will produce a true
Speaker 1: result in every case except where both inputs or more
Speaker 1: are true, because you can have more than two inputs
Speaker 1: in an end or a nand gate. So in other words,
Speaker 1: if you have two zeros, a zero, one, or a
Speaker 1: one zero, you're gonna get a one out of a
Speaker 1: nand gate. If it's a one and one, it's going
Speaker 1: to come out as a zero in a nand gate, right,
Speaker 1: Then you've got the or gate, and or gate will
Speaker 1: produce a true result if at least one of the
Speaker 1: inputs is true, so zero, one, one, zero, and one
Speaker 1: one will all produce a one. Only zero zero produces
Speaker 1: a zero or a false statement. Then you've got the
Speaker 1: Nora gate, which is not or It will produce a
Speaker 1: true result if both inputs are false, so zero zero
Speaker 1: will produce a one zero, one one zero and one
Speaker 1: one will produce a zero. Then you have now all
Speaker 1: of those gates, the the and nand or and nor
Speaker 1: gates can receive multiple inputs. And in order to really
Speaker 1: kind of sort this out, I know it sounds confusing,
Speaker 1: you can actually build a truth table. A truth table
Speaker 1: is essentially just a it's like it's almost like a spreadsheet,
Speaker 1: and it shows you what each scenario, what the outcome
Speaker 1: would be for that particular scenario for that particular gate.
Speaker 1: So like if A equal zero and be equal zero,
Speaker 1: results C will equal whatever I should say result Q
Speaker 1: because that's typically how they label it in uh in diagrams. Yeah,
Speaker 1: they usually use a que to differentiate, so there's no
Speaker 1: confusion that it's zero. They they you use a que
Speaker 1: so that you get the ideas. Oh yeah, that's the output.
Speaker 1: Um yeah, I was just gonna say that truth table
Speaker 1: kind of sounds like a medieval torture device. Him on
Speaker 1: the truth table, nobody resists the machine. I really don't
Speaker 1: know what that would do to you. Um Now I
Speaker 1: just quote Princess Bride, but of this, I was gonna
Speaker 1: say that there's an extra bonus movie quote. Remember this
Speaker 1: is for posterity, so please be honest. There are two
Speaker 1: more gates. Two more gates. Yes, there's X or the
Speaker 1: exclusive or gate, which produces a true result if the
Speaker 1: two inputs are different. So if a zero, zero or
Speaker 1: one one comes into an ex or gate, you're gonna
Speaker 1: get a zero, right if you get a if it's
Speaker 1: one zero or zero, one going into an ex orgate
Speaker 1: get a one. Uh. Now, because of the nature of
Speaker 1: this gate, it can only accept two inputs. You cannot
Speaker 1: you cannot have multiple inputs beyond two in an x
Speaker 1: or gate because it has to be specifically geared that way. Right,
Speaker 1: because because it has to be if it if it's if,
Speaker 1: if they have to be different. Uh, then there are
Speaker 1: only two choices, right, there's a zero, there's a one.
Speaker 1: If you have three inputs going into something and they
Speaker 1: have to be different and there's only two choices, there's
Speaker 1: no way two of those inputs have to be the same.
Speaker 1: Bye bye again following logic. So therefore, and an ex
Speaker 1: or gate, only two inputs can go into that gate.
Speaker 1: Then you have the x nore gate and it produces
Speaker 1: a true result if both inputs are the same. So
Speaker 1: if a zero zero or a one one goes into
Speaker 1: an exnore gate, you get a one. Otherwise you get
Speaker 1: a zero. Same thing as the ex or gate in
Speaker 1: that you can only have two inputs going into that gate. Now,
Speaker 1: using these gates that we have just described here, if
Speaker 1: you build you can actually build up a circuit using
Speaker 1: those as their basic building blocks. In fact, you can
Speaker 1: go to a hobby store and buy chips that have
Speaker 1: logic gates built onto them. Yes, and we were talking
Speaker 1: about the the RDU know a few weeks ago, And
Speaker 1: these are the kinds of projects now if you can
Speaker 1: get a basic grip on this, these are the kinds
Speaker 1: of things that you can add to your projects if
Speaker 1: you're doing um hobbies yourself and want to do this. Now,
Speaker 1: you know, once you get a basic understanding of this,
Speaker 1: you can make much more complex projects. Yeah, so, uh
Speaker 1: you know, we you can consider building a circuit using
Speaker 1: this as as using combinational logic. You're combining various gates
Speaker 1: together in order to get a different results. So you
Speaker 1: might have three inputs going into a system, and then
Speaker 1: you you align various gates in a very in a
Speaker 1: particular sequence in order to get a different result, and
Speaker 1: it all will obey the laws of the truth tables. Now,
Speaker 1: these these circuits can get pretty lunkey and pretty complex,
Speaker 1: which is why we've sort of abandoned the uh you know,
Speaker 1: it works great as a concept. In reality, we've virtualized
Speaker 1: a lot of this since then because it just otherwise
Speaker 1: it would just be a massive piece of hardware in
Speaker 1: order to build a really really complex circuit um. But
Speaker 1: you you can actually lay these out in various configurations
Speaker 1: to get different results. So it might you might have
Speaker 1: uh two inputs going into and and UH gate and
Speaker 1: another input going into a not gate, and then those
Speaker 1: the results of those um of those particular functions will
Speaker 1: go into a third gate and then now that way
Speaker 1: you have something coming out like maybe the maybe those
Speaker 1: are both going into an ex or gate, and then
Speaker 1: whatever the result is is what you're looking for. Uh. These,
Speaker 1: like I said, get pretty clunky pretty fast. The interesting
Speaker 1: thing is you can actually replace the function of some
Speaker 1: of these gates using other gates. You just have to
Speaker 1: put them in the right configu duration to do so.
Speaker 1: So you can think of some of these gates is
Speaker 1: almost being like shorthand like this gate does this one
Speaker 1: function and so therefore uh it does it um. You know,
Speaker 1: that's all it does. You just put that in this place.
Speaker 1: But sometimes you might be working with a system where
Speaker 1: you don't want to have lots of different types of gates.
Speaker 1: You want to use maybe one or two types of
Speaker 1: gates and you don't want to have to deal with
Speaker 1: all the others. Well you can do that. You just
Speaker 1: have to build the gates in the proper sequence in
Speaker 1: order to get the result you want, UH for it
Speaker 1: to to copy the function of one of the other gates.
Speaker 1: And there's various ways of doing this. Now, it does
Speaker 1: mean that you're going to use more gates overall usually
Speaker 1: than you would if you were using the the different types,
Speaker 1: but you would all be using the same type of gates.
Speaker 1: So you're you've reduced it to a single type of gate,
Speaker 1: but you you're using more of that particular gate than
Speaker 1: you would if you were using multiple types of gates.
Speaker 1: Sounds a little complicated, but it does. It does mean
Speaker 1: that when you're sketching it out, it really cuts down
Speaker 1: on the sort of gates that you have to design
Speaker 1: when you're when you're at least conceptually building your circuitry. Now,
Speaker 1: go ahead, and I was just gonna say that these
Speaker 1: these gates can be run in parallel or in a series,
Speaker 1: and um it actually kind of reminds me in a
Speaker 1: way of a very complex UH railway, because I mean,
Speaker 1: you're basically using these switches to control the flow of
Speaker 1: information in your electronic device. Um So as a you know,
Speaker 1: as someone would watch the board and make sure that
Speaker 1: the trains don't collide. Um. You're also sort of you know,
Speaker 1: you can actually control the way information flows through the
Speaker 1: device using these switches, and you can place them in
Speaker 1: ways that make the most sense to to what you're
Speaker 1: trying to carry out, which is essentially what you just said.
Speaker 1: But um, it helps me think about this conceptually, to
Speaker 1: put it in and out analogy from that to something
Speaker 1: that I can think about, like trains, because trains are
Speaker 1: nice and and if you wanna, you know, if you
Speaker 1: really want to get into this, each of these gates
Speaker 1: has a particular um graphical representation of you know, what
Speaker 1: it does. So it's I'm not bothering describing it on
Speaker 1: the podcast because this is an audio podcast. It would
Speaker 1: be kind of it would be kind of pointless to
Speaker 1: do it. And the shapes, the shapes aren't you know,
Speaker 1: like a circle or a triangle or a square something
Speaker 1: that is uh easy to describe, a lot of these
Speaker 1: shapes are modifications of those types of things. So you
Speaker 1: might say a trianglar looking thing, but you're really not
Speaker 1: going to get it. It makes more sense to actually
Speaker 1: go to a website that has them all laid out,
Speaker 1: and then once you learn what the the sort of
Speaker 1: graphic representation of a gate what it looks like. You
Speaker 1: can start looking at um the combination of gates and say, oh,
Speaker 1: well that's an and gate. So that means that since
Speaker 1: I know that and gates always give a result, that is,
Speaker 1: it will produce a true result only if both inputs
Speaker 1: are true. I know what the output of this end
Speaker 1: gate will be depending upon the inputs. So, because it's
Speaker 1: always going to behave the same way, it's never going
Speaker 1: to behave uh in a way opposite or different unless
Speaker 1: you you know, well never, it will never do that.
Speaker 1: It's only if you were using a nand gate that
Speaker 1: it would be different than the way it normally is. UM.
Speaker 1: So that way, since you know how each gate behaves
Speaker 1: in any specific circumstance given time, you can decipher what
Speaker 1: a fairly complex diagram will do. You just say, all right,
Speaker 1: I know that this gate always behaves this way. Therefore,
Speaker 1: this is what would happen given this particular series of inputs.
Speaker 1: You can actually build out a truth table for a
Speaker 1: complex circuit that way, and you will ultimately know what
Speaker 1: the circuit will produce given any particular set of circumstances. Now,
Speaker 1: the more complex a circuit gets the wider that truth
Speaker 1: table is gonna be, and the more you're gonna have
Speaker 1: to really check to make sure you're following the logical
Speaker 1: rules so that the results are are accurate, um other
Speaker 1: and we call this, we actually call this programming a circuit.
Speaker 1: Even though you might think of programming is something you
Speaker 1: do sitting down typing on a keyboard. This and this
Speaker 1: involves actual physically hooking up wires to logic gates in
Speaker 1: whatever sequence or series you need. Uh, we still call
Speaker 1: that programming. Yeah, an engineer might graft this out using
Speaker 1: these symbols on a piece of paper to get an
Speaker 1: idea of how it works. But logic gates can be
Speaker 1: very very small. I mean, we're we we've talked about
Speaker 1: the manufacture of transistors before. I mean, you can have
Speaker 1: millions of transistors and a very small piece of silicon
Speaker 1: and the logic gates I mean, using the metal oxide
Speaker 1: semiconductor UH type, which is apparently predominant according to Access
Speaker 1: Science and manufacturing today, you can have many, many of
Speaker 1: these devices. So it helps I mean, I think it
Speaker 1: would help me if I were trying to figure out
Speaker 1: exactly how I wanted to lay out this device to
Speaker 1: have it you know, drafted out with these symbols and
Speaker 1: get an idea of how it's it's working. I'm sure
Speaker 1: a lot of them use computers. Actually have a program
Speaker 1: that I use for information architecture that has a template
Speaker 1: with all these symbols on there, and then you can,
Speaker 1: you know, put it up on the screen and get
Speaker 1: an idea of how it works. But that's far larger
Speaker 1: than the actual devices because the manufacturing process can make
Speaker 1: them very very tiny, right, And as we've said in
Speaker 1: other podcasts, this is part of why miniaturization has some
Speaker 1: uh some challenges, uh that go along with it. I mean,
Speaker 1: there are a lot of different challenges, but one of
Speaker 1: the challenges is that by getting these gates to be
Speaker 1: smaller and smaller, each each element on a transistor is
Speaker 1: decreasing in size. Remember, if we're following Moore's law, then
Speaker 1: ideally you're going to be able to fit twice as
Speaker 1: many discrete elements on a chip within twenty four months,
Speaker 1: or at least the the number of discrete elements on
Speaker 1: a chip will be twice as many as it would
Speaker 1: have been twenty four months before, so two years before
Speaker 1: um with that, with those elements decreasing in size. At
Speaker 1: that pace, you start to run up against some pretty
Speaker 1: challenging issues and we've talked about it several times on
Speaker 1: the podcast before, Like electron tunneling. So if you have
Speaker 1: a gate that determines how what the result it needs
Speaker 1: to be from any given inputs, um, if you have
Speaker 1: an electron that can tunnel past that gate, then it
Speaker 1: overrides the function of that gate, which means it will
Speaker 1: start creating errors in your calculations. You know, you think
Speaker 1: about these these gates being so small that electron can
Speaker 1: tunnel through them. And by the way, electrons don't really
Speaker 1: tunnel through them, they just appear on the other side
Speaker 1: of the gate. Actually, if you think of it this way,
Speaker 1: think of as an electron as just being a uh.
Speaker 1: It's you can predict that electron will appear somewhere within
Speaker 1: a given area, all right, but you don't know the
Speaker 1: specific location of that electron. So within a given area,
Speaker 1: think of it like a sphere. You've got the sphere,
Speaker 1: and somewhere inside that sphere is this electron. Right as
Speaker 1: that sphere approaches the gate, then part of that sphere
Speaker 1: is going to go over the gate. Uh and meaning
Speaker 1: that the electron could in theory somehow exists on the
Speaker 1: other side of that gate without passing through it. That
Speaker 1: means that because there is a chance that the electron
Speaker 1: could somehow exist on the other side of that gate
Speaker 1: without passing through it, sometimes it does. Because there's a chance,
Speaker 1: yes and anything that if there is a chance for
Speaker 1: something to happen eventually, sooner or later, it happens. So
Speaker 1: that's the definition of chance. If there's no chance that
Speaker 1: it won't happen. So right, exactly, there's Schrodinger shake fist.
Speaker 1: Actually it's more like Heisenberg's and certainty principle. But anyway, um,
Speaker 1: but I was thinking you just weren't sure about it,
Speaker 1: right exactly, there you go. So anyway, the electron, because
Speaker 1: it can sometimes be on the other side of that gates.
Speaker 1: Sometimes it is on the other side of that gate.
Speaker 1: That's one of the challenges we have when we get
Speaker 1: these these gates at these tiny, tiny size. You know
Speaker 1: that the thickness is not thick enough to prevent electron
Speaker 1: tunneling unless start switching to other materials which are more
Speaker 1: resistant to electron tunneling, which is so complex. I still
Speaker 1: have not gotten a good grip on it. So I
Speaker 1: can't really explain why that is. I just know that
Speaker 1: really smart people at Intel have figured it out. Anyway. Uh,
Speaker 1: that's one of the reasons why we talk about this
Speaker 1: miniaturization process being a challenge to keeping Moore's Law going
Speaker 1: because remember More's Law is not truly a law, it's
Speaker 1: an observation, and companies are struggling to make sure that
Speaker 1: they meet the expectation laid out in that observation and
Speaker 1: self fulfilling prophecy. Yes, yeah, because once More's Law ends,
Speaker 1: then you know, the chaos will rain and robots will
Speaker 1: take over the earth and etcetera, and zombies and brains anyway.
Speaker 1: So um again, because logic gates are the very basis
Speaker 1: of these calculations. If the electron ignores the logic gate,
Speaker 1: computing stops working. So that's why we talk about electron tunneling,
Speaker 1: quantum mechanics, and quantum engineering in relation to microprocessors, because
Speaker 1: they're built on this foundation of logic gates and they
Speaker 1: are basic. Microprocessor is going to be so complex that
Speaker 1: to sketch it out and a logic gate formation would
Speaker 1: be pretty intense. But the nice thing is you can
Speaker 1: learn the basics of this pretty simply, like I said,
Speaker 1: you go to a couple of websites and look at
Speaker 1: how the logic gates are are displayed in a in
Speaker 1: a sketch. And you can even go out to a
Speaker 1: hobby store and buy chips that have logic gates on
Speaker 1: them and learn how to hook them up yourself and
Speaker 1: see it in action. It's pretty cool. It's a it's
Speaker 1: a neat project. There's a neat way to really start
Speaker 1: getting your feet wet in designing electronics, and there are
Speaker 1: plenty of different tutorials out there to explain how to
Speaker 1: do that and what why you would do that, Like
Speaker 1: you know, yeah, I've hooked up a lot of wires
Speaker 1: to this thing and it's doing this thing, but I
Speaker 1: have no idea why it's doing it or or what's
Speaker 1: the purpose. This is just the foundation, the building blocks
Speaker 1: um and then hopefully maybe in the future podcasts we
Speaker 1: can go into stuff like sequential logic, as we're talking
Speaker 1: about combinational logic right now. Sequential logic depends on other
Speaker 1: concepts like state, like an information state. You know, we
Speaker 1: say that an information has state if it carries over
Speaker 1: information from previous calculations. If I were to give you
Speaker 1: a simple calculation. If I were to say, all right,
Speaker 1: add one variable to another variable and you get a
Speaker 1: sum of those two variables. All right, Well, there's no
Speaker 1: state in that in that function I just gave you,
Speaker 1: because you could take any two variables you wanted and
Speaker 1: you're going to get a sum. But there's that that
Speaker 1: sum has no information on it based upon the previous
Speaker 1: two numbers you added to it, right, Because you might say,
Speaker 1: all right, for this one, I'm going to add three
Speaker 1: and four I got seven, And this one i'm gonna
Speaker 1: add five and nine I got fourteen, and they have
Speaker 1: no bearing on each other. Information that has a state
Speaker 1: has bearing upon previous calculations, and that's very important for computing.
Speaker 1: Without it, computers would own we be able to do
Speaker 1: really one function and then the next function will have
Speaker 1: nothing to do with the next uh with the with
Speaker 1: the one you did before. So it would be impossible
Speaker 1: to really build a program. You would have to have
Speaker 1: something that has some form of state so it can
Speaker 1: build upon what has come previously. That really goes into
Speaker 1: sequential logic. It's its own thing. We will tackle that
Speaker 1: in a different podcast, because that's gonna have some more
Speaker 1: kind of complex conversations to kind of get into you know,
Speaker 1: what sequential logic is, what it means, and how do
Speaker 1: we achieve it. But but really you can't get there
Speaker 1: without first looking at the logic gates issue. So I
Speaker 1: want to thank our listeners who have requested logic Gates
Speaker 1: because it is a really important topic. It's a really
Speaker 1: fun topic really if you like puzzles. I I was
Speaker 1: telling Chris before this that symbolic logic is one of
Speaker 1: my was one of my favorite classes in college. I
Speaker 1: was in English literature major with a focus on shakespearean
Speaker 1: uh drama, but somehow symbolic logic became one of my
Speaker 1: favorite classes because it just made sense to me. And
Speaker 1: I love these sort of puzzles where you just you
Speaker 1: look at this big picture and it looks really complex
Speaker 1: and really overwhelming, but if you just know the rules,
Speaker 1: with enough time and attention, you can figure out how
Speaker 1: it all works. And that's amazing. I don't know, I'm
Speaker 1: pretty illogical. I'm not sure. Well I I when I'm
Speaker 1: saying you, I really mean me, I don't mean you
Speaker 1: you Okay. So anyway, that covers our episode on logic gates.
Speaker 1: If you have any requests for particular episodes, whether they
Speaker 1: be really technical or not so technical, just let us know.
Speaker 1: You can say as an email that address is tech
Speaker 1: stuff at how stuff Works dot com, or you can
Speaker 1: send us a request via Twitter or Facebook or handle
Speaker 1: at both of those is tech Stuff h SW. And
Speaker 1: we should also point out recently we launched a brand
Speaker 1: new iPad app, So if you are an iPad owner
Speaker 1: like the fellow sitting across the table for me, and
Speaker 1: you want to have some fun with a new app
Speaker 1: that has a lot of our great content all bundled
Speaker 1: in their specifically designed for the layout on the iPad,
Speaker 1: check that out because it's been, uh, it's been really
Speaker 1: impressing everyone around the office for a couple of weeks,
Speaker 1: and now that it's out there in the wild, we're
Speaker 1: really excited to see what people think. And Chris and
Speaker 1: I will talk to you again, hopefully with a little
Speaker 1: bit of logic really soon. Be sure to check out
Speaker 1: our new video podcast, Stuff from the Future. Join How
Speaker 1: Stuffwork staff as we explore the most promising and perplexing
Speaker 1: possibilities of tomorrow. The House Stuff Works iPhone app has arrived.
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