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Brought to you by the reinvented two thousand twelve

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get in touch with technology? With tech

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Stuff from how stuff works dot com.

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Hello everyone, welcome to tex Stuff.

0:19

My name is Chris Pollette and I am an editor

0:21

how stuff works dot Com, sitting

0:23

across from me, as always his senior writer, Jonathan

0:25

Strickland, logic clearly dictates

0:27

that the needs of the many outweigh the needs

0:30

of the few. Okay,

0:33

so today we're going to plug

0:35

Thank you. Today we're gonna talk about logic

0:37

gates. But before we get started, let's let's

0:39

let's begin with a little Facebook feedback

0:42

you. This comes from James

0:44

and James's suggestion Electronics

0:46

one oh one logic gates. Thanks

0:49

James, it was an easy one. Yes,

0:51

we're going to tackle that, but before we do, I

0:53

have a little listener mail. This

1:00

listener mail comes from Chris and not

1:02

the Chris who's sitting across from me. Chris

1:04

says, you say in your three hundred episode that machine

1:07

code can't be easily read by humans.

1:09

That got me thinking humans made machines.

1:11

I understand that the best concept at the time

1:13

was to code computers and machines with this complicated

1:16

and unreadable language. But in

1:18

this day and age, why don't we build

1:20

computers and machines that can understand our language.

1:23

It just seems to me that some kind of cycle humans

1:25

build machines that only understand a complicated

1:27

language, we adapt to that language, and we build

1:29

programs that translate a simpler language

1:31

to the machine language. Is it possible

1:33

for computers and machines to be built to

1:36

process information in the languages

1:38

we are accustomed to? Now

1:41

these two items are actually

1:43

related to one another. You might think,

1:45

well, one of these we're talking about natural language,

1:47

and the other one we're talking about logic gates. How do those

1:50

end up being related? Well, it's

1:52

because machine code is based

1:55

upon the binary system

1:57

zeros and ones and logics

2:00

are as well. And it turns out

2:03

that the way we've built computers

2:05

is based upon this binary

2:08

system, and that's why we have machine

2:10

code. It's this two humans. It's

2:12

a it's a complex way of trying

2:15

to get a machine to do a relatively simple

2:17

task, or at least one that seems simple to

2:19

us. And unfortunately,

2:21

there is not an easy way to translate

2:25

natural human language into

2:27

machine code in order to make a machine

2:29

understand natural language in a on

2:32

a fundamental level, like on a

2:34

mechanical level, we would have to completely

2:38

change the foundation

2:41

of computing. Yeah,

2:43

so that's why it's a big deal. Uh.

2:45

You know. Instead, what we do is we end up building

2:47

programs that can understand

2:50

on on a superficial

2:53

level what natural language is

2:55

and translated into machine code so that

2:57

a computer can respond the proper way.

3:00

It's not true understanding, because again,

3:02

a computer is just running processes.

3:05

It's just running, uh, series

3:07

of calculations using these zeros

3:09

and ones and logic gates

3:11

are the very foundation of

3:13

that. It's the foundation of circuit treats, the foundation

3:16

of electronics, and the foundation of computers.

3:19

But it kind of goes back a long way

3:21

back, in fact, before there were electronic

3:23

computers. Oh yeah, I mean, because

3:26

you know, I I think of it as, uh, well,

3:28

we actually have an interesting article about

3:31

it, um about something that has come

3:33

up with a couple of centuries ago by

3:36

a guy named George. Yeah

3:38

you know. Oh yes,

3:42

because logic gates operate using Boolean

3:44

logic, we have then there is an article

3:47

on how Boolean logic works, on how stuff

3:49

works dot com, I recommend actually, which is basically

3:51

about logic gates, which

3:53

is kind of funny. I had no idea

3:55

until I started doing research on it um

3:59

because we also have a an article about how

4:01

electronic gates work on the

4:04

the the site. But there's they're

4:06

sort of hand in hand. It's better probably to go back

4:08

through the bully and logic article first

4:11

and then go to the other um.

4:13

But yeah, I mean, he basically

4:15

figured out how to use uh, you

4:17

know, I guess it's sort of the marriage

4:20

of language and mathematical

4:22

operation in some ways, wouldn't you say?

4:25

Yeah? And I also tend

4:27

to to relate it back

4:29

to symbolic logic, which is another

4:31

way of marrying mathematics

4:34

with language. Now, if you're not familiar, symbolic

4:36

logic is a concept where

4:39

you reduce statements to sort

4:42

of almost like an equation, and

4:44

using the equation form, you evaluate

4:47

that statement to determine whether or not the

4:49

statement or the combination of statements

4:51

is true or faulse um.

4:53

And you know, you have to make

4:56

some certain assumptions in order to do that,

4:58

but you can build more and more complex

5:01

equations using all these

5:03

series of statements to determine if the ultimate

5:05

conclusion is true

5:08

or false, and by true or faulse, we're really talking about

5:10

whether the argument holds water

5:13

or not. So you can actually do

5:15

this. You could take a debate and

5:17

you could take one person's side of the debate,

5:20

reduce it to this sort of mathematical

5:22

equation, and then determine whether or not

5:25

the ultimate outcome of that of

5:27

that person's side of the debate makes

5:30

sense from a logical standpoint. Yeah.

5:32

Now again we're talking logic here. We're not talking

5:35

about, uh, you know, trying

5:37

to get someone to agree to something based

5:40

upon its emotional weight, but

5:42

simply does this argument makes sense?

5:44

Does it follow the rules of logic? Yeah?

5:47

And a lot of these UM when we talk about

5:50

the logic gates UM,

5:52

they're actually devices inside electronics

5:55

that use these logical

5:57

operators, these rules, these

5:59

rules within the machine.

6:02

Basically, they're passing instructions based

6:04

on the type of circuit they are and according I actually

6:06

look this up in Access Science, which is UM

6:09

a really awesome database for for technical

6:12

things like this. UM. Basically, the

6:14

Access Science said that if you're creating

6:16

a gate circuit UM, they could be

6:19

made up of transistors, diodes, or resistors,

6:21

in some combination. Now most today

6:23

are are generally transistors only,

6:27

but they could be made up a variety of components um

6:30

and they're they're basically, you know,

6:32

you hook these up, and you can hook

6:34

them up in a variety of different ways depending

6:36

on the type of device and what you're trying

6:38

to get it to do. Um it. We'll get

6:41

into that later, but basically, these

6:43

circuits are um

6:46

a series of components that are wired

6:48

together to perform a logical

6:50

operation within a device. So

6:53

let's start off from the very very very

6:55

basic steps. So it

6:58

all begins with bits, zeros,

7:01

and ones. Now this

7:04

these aren't just numbers zero and

7:06

one does not that doesn't that

7:08

to us, That doesn't really mean anything other than the

7:10

fact that we can do mathematical processes

7:13

using them. As as as values

7:15

zero and one um they actually

7:18

translate into other

7:20

concepts. So a zero

7:22

in an electronics system would

7:24

be a low voltage meaning

7:27

zero volts, and a one is

7:29

high voltage, meaning five volts. So a one

7:32

means you've got electrons running

7:34

through there at five vaults. Zero means there are no electrons

7:36

running through zero vaults. But

7:38

a zero also would mean a false statement.

7:43

One means a true statement. Zero

7:45

could also be thought of as being on in the

7:47

off position. One is in the on

7:49

position. So let's

7:53

we have to do. You know, zero and one is kind

7:55

of shorthand of saying. So if we're talking about zeros,

7:57

we're talking about false, and we're talking about once, we're

7:59

talking about true. For time about zero's we're talking about low

8:01

voltage. If we're talking about one, we're talking about high voltage.

8:04

This is how we translate ideas

8:07

conceptually into a

8:09

real device, a physical device

8:12

that does something one

8:15

there we go true. So now

8:18

a logic gate will process

8:20

a signal and what it does

8:22

to that signal, like it has an input

8:24

and an output, what it does to that

8:26

signal when it comes in through the input

8:29

is based upon two things. The

8:31

nature of the logic gate, because there are

8:33

several different basic types of

8:35

logic gates, and the

8:37

whether or not the input was true or

8:40

false, so whether or not it was a

8:42

one or a zero. Those

8:44

two elements will determine what the

8:46

output of that specific logic

8:49

gate is. And the simplest logic

8:51

gate is a not git

8:53

that's also known as an inverter. Yes, Now

8:56

inverters what they do is, they will take an

8:58

input and switch it to the

9:00

opposite output. So, in other

9:02

words, if a zero is fed

9:05

into a not gate, it

9:07

will produce a one. So

9:09

false statement comes into a not gate, it flips

9:11

it to a true statement coming out right,

9:14

all right, so or against

9:16

low voltage to high voltage, yes, vice versa.

9:19

So whatever the signal coming into the

9:21

the not gate is, the

9:23

opposite goes out. Now

9:25

it can only have one input,

9:28

which makes it unique among the

9:30

gates. The other gates have two

9:32

or more inputs, and they combine the

9:34

two in order to produce a result. Alright,

9:38

So then the next one would

9:40

be an and gate. Now

9:43

and gates will produce a true

9:45

result only if both

9:47

inputs coming into the gate are

9:49

also true. I think of that like

9:52

the programming statement if then if

9:55

both are true, then it will return

9:58

true results. So that means

10:00

that let's say imagine that you have this.

10:03

You can actually imagine that this is a gate and

10:05

there are two roads leading into the gate, and you

10:07

have two cars going up to the

10:09

gate. If both cars are

10:12

are true, then you've

10:14

got a true result coming out. Otherwise you have a false

10:16

result coming out. Actually, it would be and if

10:18

and only if yes. So,

10:21

in other words, if you have to If you have these

10:23

two uh inputs

10:25

coming into the and gate and both are

10:28

a one, so both are true, both are

10:30

high voltage, you get a one as

10:32

a result. Any other combination you get

10:34

a zero as a result a false statement

10:37

or low voltage. Zero and one

10:40

will equal zero. In this case, zero

10:42

zero will be zero, zero one will

10:44

be zero, one zero will be zero

10:46

because you have to think of all three

10:49

instances that way. Even though you might say,

10:51

wait, zero one and one zero, isn't that the same

10:53

thing? No, Because you're talking about two different

10:55

inputs coming into a gate, and

10:58

those two inputs are coming from two different sources.

11:01

Sometimes yeah, sometimes

11:03

they come from the same source, but usually they come from two different

11:05

sources. And that means that because

11:08

they're coming from two different sources, you have two different configurations.

11:10

You have one where one is true and one is faults,

11:13

and another one where one is faults and the other is true.

11:16

Sounds kind of complicated, it's actually pretty simple. And

11:18

again, if this starts to sound confusing,

11:20

check out these articles that we have on our site because

11:22

they will help illustrate these concepts.

11:25

So, besides the end gate, you have the

11:28

nand gate or not and

11:31

now and not and will produce a

11:33

true result in every case except

11:36

where both inputs or more

11:38

are true, because you can have more than two

11:40

inputs in an end or a nand gate.

11:43

So in other words, if you have two zeros,

11:45

a zero, one, or a one zero, you're

11:48

gonna get a one out of a nand gate.

11:50

If it's a one and one, it's going to come out

11:52

as a zero in a nand gate, right,

11:56

Then you've got the or gate, and

11:58

or gate will produce a true

12:00

result if at least one of the

12:02

inputs is true, so

12:05

zero, one, one, zero, and one one

12:07

will all produce a one. Only zero

12:09

zero produces a zero or a false

12:12

statement. Then you've got the Nora

12:14

gate, which is not or It will produce

12:16

a true result if both inputs are false,

12:19

so zero zero will produce a one

12:22

zero, one one zero and one one will

12:24

produce a zero. Then

12:26

you have now all of those gates, the

12:28

the and nand or and

12:30

nor gates can receive multiple

12:33

inputs. And in order to really kind

12:35

of sort this out, I know it sounds confusing,

12:37

you can actually build a truth table.

12:39

A truth table is essentially just a it's

12:41

like it's almost like a spreadsheet, and it shows

12:44

you what each scenario,

12:47

what the outcome would be for that

12:49

particular scenario for that particular gate. So

12:52

like if A equal zero and

12:54

be equal zero, results C

12:56

will equal whatever I

12:59

should say result Q because that's typically

13:01

how they label it in

13:03

uh in diagrams. Yeah, they

13:05

usually use a que to differentiate,

13:07

so there's no confusion that it's zero. They

13:10

they you use a que so that you get

13:12

the ideas. Oh yeah, that's the output. Um

13:15

yeah, I was just gonna say that truth table kind

13:17

of sounds like a medieval torture device. Him

13:20

on the truth table, nobody

13:24

resists the machine.

13:27

I really don't know what that would do to you. Um

13:31

Now I just quote Princess Bride, but of

13:33

this, I was gonna say that there's an

13:35

extra bonus movie quote. Remember

13:37

this is for posterity, so please be honest.

13:41

There are two more gates. Two more gates. Yes, there's X

13:43

or the exclusive or gate, which

13:46

produces a true result if the two

13:48

inputs are different. So if

13:50

a zero, zero or one one comes into

13:52

an ex or gate, you're gonna get a zero, right

13:55

if you get a if it's one zero or

13:57

zero, one going into an ex orgate

14:00

get a one. Uh. Now, because

14:02

of the nature of this gate, it can only

14:04

accept two inputs. You cannot

14:07

you cannot have multiple inputs beyond two

14:10

in an x or gate because it has to be specifically

14:13

geared that way. Right, because because it

14:15

has to be if it if it's if,

14:17

if they have to be different. Uh,

14:20

then there are only two choices, right, there's

14:22

a zero, there's a one. If you

14:24

have three inputs going into something

14:26

and they have to be different and there's only two choices,

14:28

there's no way two of those inputs have to be the

14:30

same. Bye bye again

14:32

following logic. So therefore, and an

14:35

ex or gate, only two inputs can

14:37

go into that gate. Then you have the

14:39

x nore gate and it produces

14:41

a true result if both inputs are the same.

14:44

So if a zero zero or a one one

14:46

goes into an exnore gate, you get a one.

14:48

Otherwise you get a zero. Same thing as the

14:51

ex or gate in that you can only

14:53

have two inputs going into that gate.

14:56

Now, using these

14:58

gates that we have just described here, if

15:00

you build you can actually build up a

15:02

circuit using those as their basic

15:05

building blocks. In fact, you can go to a hobby

15:07

store and buy chips that have logic

15:09

gates built onto them.

15:12

Yes, and we were talking about the

15:14

the RDU know a

15:16

few weeks ago, And these are the kinds of

15:18

projects now if you can get a

15:20

basic grip on this, these are the kinds of things that you

15:22

can add to your projects if you're doing um

15:25

hobbies yourself and want to do this. Now,

15:28

you know, once you get a basic understanding of this, you can make

15:30

much more complex projects. Yeah, so,

15:33

uh you know, we you can consider

15:35

building a circuit using this as as using

15:37

combinational logic. You're combining various

15:40

gates together in order to get a different

15:42

results. So you might have three

15:44

inputs going into a system, and then you

15:47

you align various gates in a

15:49

very in a particular sequence in

15:52

order to get a different result, and it

15:55

all will obey the laws of the truth

15:57

tables. Now, these these circuits can get

15:59

pretty lunkey and pretty complex,

16:01

which is why we've sort of abandoned

16:03

the uh you know, it works great

16:06

as a concept. In reality, we've virtualized

16:08

a lot of this since then because it just otherwise

16:10

it would just be a massive piece of hardware

16:12

in order to build a really really complex circuit

16:15

um. But you you can actually

16:17

lay these out in various configurations

16:20

to get different results. So it

16:22

might you might have uh two

16:24

inputs going into and

16:26

and UH gate and

16:28

another input going into a not gate, and

16:30

then those the results

16:32

of those um of those particular

16:35

functions will go into a third gate

16:37

and then now that way you have something

16:40

coming out like maybe the maybe those are both going

16:42

into an ex or gate, and

16:44

then whatever the result is is what you're looking

16:46

for. Uh. These,

16:50

like I said, get pretty clunky pretty fast. The

16:52

interesting thing is you can actually replace

16:54

the function of some of these gates

16:57

using other gates. You just have to put

16:59

them in the right configu duration to do so.

17:02

So you can think of some of these gates is almost being like

17:04

shorthand like this gate does this one

17:06

function and so therefore uh

17:08

it does it um. You know, that's all it does.

17:11

You just put that in this place. But sometimes

17:13

you might be working with a system

17:15

where you don't want to have lots of different

17:17

types of gates. You want to use

17:19

maybe one or two types of gates and you don't

17:21

want to have to deal with all the others. Well

17:24

you can do that. You just have to build

17:26

the gates in the proper sequence in

17:28

order to get the result you want, UH

17:31

for it to to copy the function of

17:33

one of the other gates. And there's various ways of doing

17:35

this. Now, it does mean that you're going to use more

17:38

gates overall usually than

17:41

you would if you were using the the different

17:43

types, but you would all be using the same

17:45

type of gates. So you're you've reduced it to

17:47

a single type of gate, but you

17:50

you're using more of that particular gate

17:52

than you would if you were using multiple types

17:54

of gates. Sounds a little

17:56

complicated, but it does. It

17:58

does mean that when you're sketching it out, it

18:01

really cuts down on the sort of gates that

18:03

you have to design when you're when

18:05

you're at least conceptually building your circuitry.

18:08

Now, go

18:10

ahead, and I was just gonna say

18:12

that these these gates can be run in parallel

18:15

or in a series, and

18:17

um it actually kind of reminds me

18:19

in a way of a very complex

18:22

UH railway, because

18:25

I mean, you're basically using these switches to

18:27

control the flow of information in

18:30

your electronic device. Um

18:32

So as a you

18:35

know, as someone would watch the board

18:37

and make sure that the trains don't collide. Um.

18:39

You're also sort of you know, you

18:42

can actually control the way information flows

18:44

through the device using

18:46

these switches, and you can place them in ways

18:48

that make the most sense to

18:51

to what you're trying to carry out, which is essentially what

18:53

you just said. But um,

18:55

it helps me think about this

18:57

conceptually, to put it in and out

19:00

analogy from that to something that I

19:02

can think about, like trains, because trains

19:04

are nice and and if you wanna, you know, if

19:06

you really want to get into this, each of these

19:08

gates has a particular um

19:12

graphical representation of

19:15

you know, what it does. So it's

19:17

I'm not bothering describing it on the podcast because

19:19

this is an audio podcast. It would be kind of it would

19:22

be kind of pointless to do it. And the shapes,

19:24

the shapes aren't you know, like a

19:26

circle or a triangle or a square

19:28

something that is uh

19:31

easy to describe, a lot of these shapes are

19:33

modifications of those types of

19:35

things. So you might say a trianglar looking thing,

19:37

but you're really not going to get it. It makes

19:39

more sense to actually go to a website that

19:41

has them all laid out, and then once

19:44

you learn what the the sort

19:46

of graphic representation of a gate

19:48

what it looks like. You can start looking

19:51

at um the combination

19:53

of gates and say, oh, well that's an and gate.

19:55

So that means that since I know that and

19:57

gates always give a result, that

20:00

is, it will produce a true result only if both

20:02

inputs are true. I know what the output

20:04

of this end gate will be depending upon the inputs.

20:07

So, because it's always going to behave the same

20:09

way, it's never going to behave uh

20:11

in a way opposite or different unless

20:13

you you know, well never,

20:16

it will never do that. It's only if you were using

20:18

a nand gate that it would be different than

20:21

the way it normally is. UM.

20:23

So that way, since you know how each gate

20:25

behaves in any specific circumstance

20:29

given time, you can decipher

20:31

what a fairly complex diagram

20:34

will do. You just say, all right, I know

20:36

that this gate always behaves this way.

20:38

Therefore, this is what would

20:40

happen given this

20:42

particular series of inputs. You

20:45

can actually build out a truth table for a

20:47

complex circuit that way, and you will

20:49

ultimately know what the circuit will

20:51

produce given any particular

20:53

set of circumstances. Now, the more complex

20:55

a circuit gets the wider that truth table

20:58

is gonna be, and the more you're gonna have to really

21:00

check to make sure you're following the logical

21:02

rules so that the results

21:05

are are accurate, um other

21:07

and we call this, we actually call this programming

21:10

a circuit. Even though you might think

21:12

of programming is something you do sitting down typing

21:14

on a keyboard. This and

21:17

this involves actual physically hooking up wires

21:20

to logic gates in whatever

21:22

sequence or series you need. Uh,

21:24

we still call that programming. Yeah, an engineer

21:27

might graft this out using these symbols

21:29

on a piece of paper to get an idea

21:31

of how it works. But logic gates

21:33

can be very very small. I mean, we're we we've

21:36

talked about the manufacture of transistors

21:38

before. I mean, you can have millions

21:40

of transistors and a very small

21:42

piece of silicon and the

21:45

logic gates I mean, using the metal

21:47

oxide semiconductor UH

21:50

type, which is apparently predominant

21:52

according to Access Science and manufacturing

21:55

today, you can have many, many of these

21:57

devices. So it helps I mean,

21:59

I think it would help me if I were trying to figure out

22:01

exactly how I wanted to lay out this device

22:03

to have it you know, drafted out with these

22:05

symbols and get an idea of how it's it's working.

22:08

I'm sure a lot of them use computers. Actually

22:10

have a program that I use for

22:12

information architecture that has

22:14

a template with all these symbols on there, and then

22:16

you can, you know, put it up on the screen and get an idea

22:19

of how it works. But that's far larger than the

22:21

actual devices because the manufacturing

22:23

process can make them very very tiny, right, And

22:26

as we've said in other podcasts, this is

22:28

part of why miniaturization

22:30

has some uh some challenges, uh

22:33

that go along with it. I mean, there are a lot of different

22:35

challenges, but one of the challenges is that by

22:38

getting these gates to be smaller and smaller,

22:40

each each element on a transistor is

22:42

decreasing in size. Remember, if we're following Moore's

22:45

law, then ideally you're going

22:47

to be able to fit twice as many discrete elements

22:49

on a chip within twenty four

22:51

months, or at least the the number

22:53

of discrete elements on a chip will be twice

22:55

as many as it would have been twenty

22:58

four months before, so two years before um

23:01

with that, with those elements

23:03

decreasing in size. At that pace,

23:06

you start to run up against some pretty challenging

23:08

issues and we've talked about it several times on the podcast

23:11

before, Like electron tunneling. So

23:14

if you have a gate that determines how

23:17

what the result it needs to be from any given

23:19

inputs, um, if you have

23:22

an electron that can tunnel past

23:24

that gate, then it overrides

23:27

the function of that gate, which means it will

23:29

start creating errors in your calculations.

23:32

You know, you think about these these gates being so

23:34

small that electron can tunnel through them. And

23:36

by the way, electrons don't really tunnel through

23:38

them, they just appear on the other side of the gate. Actually,

23:41

if you think of it this way, think of as an electron

23:43

as just being a uh. It's

23:45

you can predict that electron will appear

23:47

somewhere within a given area, all

23:50

right, but you don't know the specific location of

23:52

that electron. So within a

23:54

given area, think of it like a sphere.

23:56

You've got the sphere, and somewhere inside

23:59

that sphere is this electron. Right

24:01

as that sphere approaches the gate,

24:04

then part of that sphere is going to

24:06

go over the gate. Uh

24:08

and meaning that the electron could

24:10

in theory somehow exists on the other

24:12

side of that gate without passing through it. That

24:15

means that because there is a chance that the

24:17

electron could somehow exist on the other

24:19

side of that gate without passing through it, sometimes

24:22

it does. Because there's a chance, yes

24:24

and anything that if there is a chance for something

24:26

to happen eventually, sooner or later, it happens. So

24:29

that's the definition of chance. If there's no chance

24:31

that it won't happen. So right,

24:34

exactly, there's Schrodinger shake

24:37

fist. Actually it's more like Heisenberg's

24:39

and certainty principle. But anyway, um, but

24:41

I was thinking you just weren't sure

24:43

about it, right exactly, there you go. So anyway, the

24:45

electron, because it can sometimes

24:47

be on the other side of that gates. Sometimes it is on

24:49

the other side of that gate. That's one of the challenges we have

24:51

when we get these these gates at these tiny, tiny

24:54

size. You know that the thickness

24:56

is not thick enough to prevent electron tunneling

24:59

unless start switching to other materials

25:02

which are more resistant to electron tunneling, which

25:04

is so complex. I still have not gotten

25:06

a good grip on it. So I can't really explain why

25:08

that is. I just know that really smart people

25:10

at Intel have figured it out. Anyway.

25:13

Uh, that's one of the reasons why we talk

25:16

about this miniaturization process being a

25:18

challenge to keeping Moore's Law going because

25:21

remember More's Law is not truly a law, it's an

25:23

observation, and companies are

25:25

struggling to make sure that they meet the

25:27

expectation laid out in that observation

25:30

and self fulfilling prophecy. Yes, yeah,

25:32

because once More's Law ends, then you

25:34

know, the chaos will rain and robots will take over the

25:36

earth and etcetera, and zombies and brains anyway.

25:39

So um again,

25:41

because logic gates are the very basis of

25:44

these calculations. If the electron

25:46

ignores the logic gate, computing

25:48

stops working. So that's why

25:50

we talk about electron tunneling, quantum

25:52

mechanics, and quantum engineering in

25:54

relation to microprocessors, because they're

25:56

built on this foundation of logic gates

25:59

and they are basic. Microprocessor is

26:01

going to be so complex that to sketch

26:03

it out and a logic gate formation would

26:06

be pretty intense. But

26:09

the nice thing is you can learn the basics

26:12

of this pretty simply, like I said, you go to a

26:14

couple of websites and look at how

26:16

the logic gates are are displayed

26:18

in a in a sketch. And you can

26:20

even go out to a hobby store and buy chips

26:23

that have logic gates on them and learn how to hook them

26:25

up yourself and see it in

26:27

action. It's pretty cool.

26:29

It's a it's a neat project.

26:31

There's a neat way to really start getting your feet

26:33

wet in designing

26:36

electronics, and there are plenty of different

26:38

tutorials out there to explain how to

26:40

do that and what why you would do

26:42

that, Like you know, yeah, I've hooked up a lot of wires to

26:44

this thing and it's doing this thing, but I

26:46

have no idea why it's doing it or or what's

26:48

the purpose. This is just

26:51

the foundation, the building blocks um

26:53

and then hopefully maybe in the future podcasts

26:56

we can go into stuff like sequential

26:58

logic, as we're talking about

27:00

combinational logic right now. Sequential

27:03

logic depends on other concepts

27:05

like state, like an

27:07

information state. You know, we

27:10

say that an information has state if

27:12

it carries over information

27:14

from previous calculations. If I were

27:16

to give you a simple calculation. If

27:18

I were to say, all right, add

27:20

one variable to another variable and you

27:22

get a sum of those two

27:25

variables. All right, Well, there's no state

27:27

in that in that function I

27:29

just gave you, because you could take any two

27:32

variables you wanted and you're going to get a sum.

27:34

But there's that that sum has

27:37

no information on it based upon the previous

27:39

two numbers you added to it, right,

27:42

Because you might say, all right, for this one, I'm going to add

27:44

three and four I got seven, And this one i'm gonna add

27:47

five and nine I got fourteen, and

27:50

they have no bearing on each other. Information

27:53

that has a state has bearing upon previous

27:56

calculations, and that's very important for computing.

27:58

Without it, computers would own we be able to

28:00

do really one function and

28:02

then the next function will have nothing to do with the

28:04

next uh with the with the one you did

28:06

before. So it would be impossible to really build a program.

28:10

You would have to have something that has some form

28:12

of state so it can build upon

28:14

what has come previously. That

28:17

really goes into sequential logic. It's its own

28:19

thing. We will tackle that in a different

28:21

podcast, because that's gonna have some more kind

28:24

of complex conversations to kind of get

28:26

into you know, what sequential logic

28:28

is, what it means, and how do we achieve

28:30

it. But but really you

28:32

can't get there without first

28:34

looking at the logic gates issue.

28:37

So I want to thank our listeners who

28:40

have requested logic Gates because it

28:42

is a really important topic. It's a really fun

28:44

topic really if you like puzzles. I I

28:46

was telling Chris before this that symbolic

28:49

logic is one of my was one of my favorite classes

28:51

in college. I was in English literature

28:54

major with a focus on shakespearean

28:57

uh drama, but somehow

29:00

symbolic logic became one of my favorite

29:03

classes because it just made sense

29:05

to me. And I love these sort

29:07

of puzzles where you just you

29:09

look at this big picture and it looks really complex

29:12

and really overwhelming, but if you just

29:14

know the rules, with enough time

29:17

and attention, you can figure out

29:19

how it all works. And that's

29:22

amazing. I don't know, I'm pretty

29:24

illogical. I'm not sure. Well I

29:26

I when I'm saying you, I really mean me, I

29:28

don't mean you you Okay.

29:31

So anyway, that covers our episode

29:34

on logic gates. If you have

29:36

any requests for particular episodes, whether

29:38

they be really technical or not so

29:40

technical, just let us know. You can say as an email

29:43

that address is tech stuff at how

29:45

stuff Works dot com, or you

29:47

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29:49

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29:52

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29:54

point out recently we launched

29:56

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29:58

So if you are an iPad owner like the fellow

30:01

sitting across the table for me, and you

30:03

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check that out because it's been, uh,

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it's been really impressing everyone around the office for

30:17

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30:19

we're really excited to see what people think.

30:22

And Chris and I will talk to you again,

30:24

hopefully with a little bit of logic really

30:27

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