Name: CS50 2018 - リーディング1 - C (CS50 2018 - Lecture 1 - C)
Uploaded: 2021-01-14T07:55:00.000Z
Duration: 2 h 12 min 26 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

SPEAKER 1: This is CS50, and this is week 1.

And by the end of the day, you will know how

This is the only language that machines ultimately understand.

But thankfully, per last week, there's so many abstractions

and there are so many humans that have come before us that we don't actually

We can abstract way above it like we did with Scratch already

But does anyone nonetheless want to take a guess

at what that program, when fed to your Mac or PC, actually does?

It's perhaps the simplest program you could write.

Indeed, it does, when fed to the brain of your computer,

Well, recall where we started this conversation last time

talking about computer science more generally

and problem solving-- we proposed could be distilled really is this.

And somewhere in the middle, you need to do something with those inputs.

And to get to that point, though, we had to represent those inputs and outputs.

We just had to decide as humans, how are we going to represent all of the inputs

to our problem when it comes time to have a computer actually process them.

And at the end of the day, all of the phones and the computers that we're all

using only at the end of the day plug into the wall

to get their physical resource, electricity,

and they might store that temporarily in a battery.

So the world really reduces to those two states, so to speak.

And so you can think of those states then as just being like a light bulb,

I pulled up my cell phone last time to turn the flashlight on or off,

Now of course, if you only have one light bulb,

But if you start to have a bunch of them back to back to back to back,

you can permute them like I did my finger--

And so we started talking about binary more generally.

And so here for instance were three sequences

of 0's and 1's and each of those represented something,

but we don't need to think about the world at that level.

All of us are so much more familiar with decimal of course,

and indeed recall that this was just 72, 73, and 33, which if anyone recalls,

which is this global standard for mapping numbers

Yeah, it was just high, capital H capital I exclamation point.

And so that's an abstraction on top of those otherwise binary numbers.

But we don't have to model just text using numbers.

At the end of the day, our only resource is still that electricity,

and the only way we think about it digitally is still zeros and ones.

72, 73, 33-- and treat them in the context of Photoshop

or a photo program or a graphics program,

we can instead interpret them as like some amount

of red, some amount of green, some amount of blue,

which gave us last time, recall, this yellowish color.

So now we had another abstraction on top of binary colors,

What can you do once you have more than one pixel?

So we're continuing the conversation up and up and up,

and we could represents something like a graphical emoji on the screen, which

It's got a whole bunch of yellow dots and other colors as well.

And recall that, if we want to animate things,

whether it's through silly things like animojis on a phone or just more proper

videos and movies, well, those are just sequences

of images flying past your human eyes really quite quickly.

So that's where we kind of left off last time starting at the base level

and abstracting away so that we could stipulate thereafter we

can represent inputs, and we can represent

And here on out, we don't need to think at that level.

We can just assume we all know how to do this.

And even if it eventually becomes kind of a distant memory,

But inside of this black box are so-called algorithms,

this is where the problems are actually solved.

And we not only talked about what these algorithms are, but for instance,

So recall that this red line represented a very simple algorithm just turning

the phone book page by page one at a time.

And the reason that it's a straight line is because there's a one to one

correspondence between how many pages there are in the book

and how many page turns there are-- one page, one more page, one more

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CS50 2018 - リーディング1 - C (CS50 2018 - Lecture 1 - C)

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