0:00:04.284,0:00:08.893
If a computer is like a piano, then the[br]term software refers to the code - what runs on it, like the music.

0:00:08.893,0:00:13.026
And the hardware is the physical parts of the thing.

0:00:13.026,0:00:15.167
So in this section, I'm going to talk about hardware, physical parts of the computer.

0:00:15.167,0:00:22.200
So probably one of the most important inventions of the twentieth century is the transistor.

0:00:22.200,0:00:27.467
And this is a little electronic component that can be used to build all sorts of different things.

0:00:27.467,0:00:32.367
The most common form of transistor today is built on what's called a chip.

0:00:32.367,0:00:36.967
And here's a picture of a chip, that I'm linking to from Wikimedia.

0:00:40.147,0:00:44.234
And so a chip is made of a little fingernail-sized piece of silicon.

0:00:44.234,0:00:46.667
And then different electronic components can be etched onto the silicon

0:00:46.667,0:00:50.267
and this allows you to essentially make the components very, very cheaply.

0:00:50.267,0:00:58.816
So the most likely, the most common component put on here is transistors. And you can make all sorts of stuff out of transistors.

0:00:58.816,0:01:04.100
So the things I'm gonna talk about later, CPUs and memory and whatnot, those all come down to chips that look like this.

0:01:04.100,0:01:08.615
Now a chip like this is said to be solid state

0:01:08.615,0:01:10.667
meaning there's no moving parts, there's no gears, there's no wheels.

0:01:10.667,0:01:13.538
And in a way, that makes it very reliable.

0:01:13.538,0:01:14.931
And as I said before, they can be made pretty cheaply.

0:01:14.931,0:01:18.100
And so this is one of the driving forces[br]in the, computer revolution.

0:01:18.100,0:01:22.033
I should point out, this is the element silicon,[br]which is like glass.

0:01:22.033,0:01:28.300
Not to be confused with silicone, which is like that kinda[br]soft, rubbery stuff.

0:01:28.300,0:01:33.633
So, one of the most important forces driving silicon development is this thing called Moore's Law.

0:01:33.633,0:01:37.600
And so this was formulated by Gordon[br]Moore. And it's just an observation about

0:01:37.600,0:01:43.120
how the manufacturing of chips with[br]transistors on them tends to go.

0:01:43.120,0:01:47.633
And what the law says is that every 18 to 24[br]months, approximately,

0:01:47.633,0:01:52.867
the number of transistors which can be fit onto one of those chips doubles.

0:01:52.867,0:02:00.906
So, you could sorta take that two ways. It might mean that for[br]each year when I make a chip

0:02:00.906,0:02:04.733
after it doubles, well, now I can make that same chip but I get twice as many transistors.

0:02:04.733,0:02:06.167
So, in some sense it... it's more powerful.

0:02:06.167,0:02:12.795
Or you can think of it as just that the transistors are just[br]getting cheaper and cheaper.

0:02:12.795,0:02:15.233
Now Moore's Law is not some law of nature, like the[br]law of gravity.

0:02:15.233,0:02:19.467
It's just an observation about how transistor manufacturing tends to go,

0:02:19.467,0:02:24.776
but it's been true for over twenty years, and it seems to be continuing to be true.

0:02:24.776,0:02:32.767
So. Moore's law is why you can have computers now that are getting cheaper and they're showing up in thermostats and microwaves.

0:02:32.767,0:02:37.872
Essentially it's the doubling quality of Moore's law,

0:02:37.872,0:02:46.742
making what used to be a computer that would fill a room and cost millions of dollars now fit in the size of a sugar cube and cost under a dollar.

0:02:46.742,0:02:49.018
That is the effect of Moore's law when you think of doubling.

0:02:49.018,0:02:50.500
Well, just one doubling it's not that big.

0:02:50.500,0:02:55.334
If you have ten doublings that's a factor of a[br]thousand.

0:02:55.334,0:02:57.935
So that's how you get from the room down to the sugar cube.

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The other way you can think about this just in your own life,

0:02:59.800,0:03:07.408
is imagine buying... maybe six years ago buying a 50 dollar mp3 player.

0:03:07.408,0:03:14.096
had some amount of capacity. Maybe it had one[br]gigabyte of capacity.

0:03:14.096,0:03:17.967
And then a few years later, with the same $50, if you[br]bought an mp3 player it might have two or maybe four gigabytes of capacity.

0:03:17.967,0:03:22.367
And then a few years later, for the same $50, well now they all have eight gigabytes.

0:03:22.367,0:03:26.267
And what's going on is, well, basically there's a chip in the mp3 player that does the storage.

0:03:26.267,0:03:30.300
And by Moore's law, the manufacturing of that chip...

0:03:30.300,0:03:33.415
because there's more transistors that fit in there,

0:03:33.415,0:03:36.733
for pretty much the same price they can offer more and more capacity.

0:03:36.733,0:03:40.167
So that is the exponential quality of Moore's law.

0:03:40.167,0:03:44.100
So, to talk about computers, I'm gonna talk about the major parts that go into one.

0:03:44.100,0:03:53.400
And largely - oh, and here's a little picture of a computer - I'm going to say that there's the CPU, which is sort of the brains of the thing;

0:03:53.400,0:03:57.656
and then there's RAM, which is sort of the temporary scratch pad memory;

0:03:57.656,0:04:01.046
and finally, disk or flash for persistent structure.

0:04:01.046,0:04:02.333
So we'll talk about each one of those parts.

0:04:02.333,0:04:09.127
So, probably the most important part of the computer is the CPU, which stands for Central Processing Unit,

0:04:09.127,0:04:12.467
and it's inevitably described as kind of "the[br]brains" of the computer. It actually does the computing.

0:04:12.467,0:04:19.767
So... the CPU has certain fairly simple operations that it can perform,

0:04:19.767,0:04:27.533
and so when you say that a computer runs at two billion operations per second,

0:04:27.533,0:04:29.900
really that's talking about the CPU: that means the CPU can do two billion things per second.

0:04:29.900,0:04:32.765
And that's a very typical number for 2012.

0:04:32.765,0:04:38.767
To say that it's the brains, we have to think[br]about, well, the 'run' button in the earlier coding exercises,

0:04:38.767,0:04:42.610
where you had the code, and then something was executing the code.

0:04:42.610,0:04:45.600
Really, that was the CPU that was taking in that code and doing it.

0:04:45.600,0:04:51.833
So, before I talk about, RAM and disk and those things, I need to have a brief word about bytes.

0:04:51.833,0:04:57.900
So a byte is the, sort of, most common measure of information storage.

0:04:57.900,0:05:02.951
So one byte refers to approximately one letter that you might type,

0:05:02.951,0:05:07.688
like a T or an X or something. That fits in one byte.

0:05:07.688,0:05:14.700
Later on I'm gonna talk about RAM and disks and things like that. And those are all the sizes. How much information can they hold?

0:05:14.700,0:05:20.333
Those are measured in bytes. And later on, I'll go into more detail about the different sizes that you might have.

0:05:20.333,0:05:24.067
For now, I'll just say that one megabyte is a common size. That's about a million bytes.

0:05:24.067,0:05:28.367
And one gigabyte is about a billion bytes.

0:05:28.367,0:05:32.500
So,with that in mind, let's go to our second bit of technology here...

0:05:32.500,0:05:38.167
So RAM stands for Random Access Memory - or we might just say 'memory'-

0:05:38.167,0:05:44.654
and RAM is the temporary storage used by the CPU

0:05:44.654,0:05:47.800
to hold data and code that it's using right then just in[br]the course of doing computation.

0:05:47.800,0:05:55.233
So in the code when we said something like 'new SimpleImage ("flowers.jpg")'

0:05:55.233,0:06:02.333
and I would say, 'well, this kind of loads the data into the[br]computer' - really what was happening is the bytes of that data were being loaded into RAM,

0:06:02.333,0:06:06.016
and once they were in RAM then the CPU could do operations on them.

0:06:06.016,0:06:09.833
could do operations on them. So when you[br]wrote code like 'pixel.setRed(0)' - really that was

0:06:09.833,0:06:14.767
going into RAM and manipulating of the data; actually making a change.

0:06:14.767,0:06:18.300
So, that sort of active stuff happens in RAM.

0:06:18.300,0:06:24.824
The main thing about RAM is that it is not persistent.

0:06:24.824,0:06:27.000
What that means is - when the power is removed, it just goes blank.

0:06:27.000,0:06:31.744
So it just works well as fast, temporary[br]storage, but it's not long-term storage.

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And you can kind of, I think you can have some[br]intuition about that if you think about when you're working on

0:06:36.067,0:06:42.500
some, you know, paper, and you're typing in a word processor and then suddenly your computer shuts down...

0:06:42.500,0:06:44.700
maybe it crashes or the power goes out or something.

0:06:44.700,0:06:50.667
And so you have a sense that, well, whatever you were just... those last few bits you were typing. Those are gone.

0:06:50.667,0:06:59.283
Those were just in RAM. And the version that you have is the version that you saved.

0:06:59.283,0:07:00.233
So in a word processor when you hit the 'save' command, really what you are doing is

0:07:00.233,0:07:05.506
you're taking the version that is in RAM - this kinda temporary version - and you're writing it to disk.

0:07:05.506,0:07:09.667
(mumbled) I'm just getting something, and we'll talk about it in a second.

0:07:09.667,0:07:14.300
So that kinda gives you the sense of what does it mean to be persistent - like disk, or volatile - like RAM.

0:07:14.300,0:07:19.577
Alright, that leads us to our third hardware component: persistent storage.

0:07:19.577,0:07:22.300
So, the main thing about persistent storage:

0:07:22.300,0:07:27.843
It's a big area of bytes, but when you remove the power the data stays there.

0:07:27.843,0:07:34.484
So for the longest time persistent storage in computers has been done with a hard drive.

0:07:34.484,0:07:40.800
So a hard drive has a spinning disk in it. And there's a little head that writes magnetic patterns on the disk,

0:07:40.800,0:07:44.467
and it does that to record 0's and 1's, and store data.

0:07:44.467,0:07:48.767
And so when you... if you have a computer and you hear kind of a high-pitched 'whining' sound,

0:07:48.767,0:07:54.800
what you're probably hearing is the hard drive disk spinning in its little enclosure.

0:07:54.800,0:07:59.500
More recently there's been advances in what's called a flash drive.

0:07:59.500,0:08:04.200
And so a flash drive also stores 0's and 1's persistently, but it's solid state.

0:08:04.200,0:08:11.868
It just uses a chip - a so-called 'flash chip' - so there's no moving parts, it's very small, it's very reliable.

0:08:11.868,0:08:14.667
So, flash chips are used to make those little USB thumb drives

0:08:14.667,0:08:19.667
or SD cards, that you might put into a camera or something like that.

0:08:19.667,0:08:26.636
It used to be that per byte, flash was much more expensive than hard drives, and so hard drives were used for everything.

0:08:26.636,0:08:28.633
Sort of following the pattern of Moore's Law,

0:08:28.633,0:08:30.491
flash chips have been getting cheaper and cheaper.

0:08:30.491,0:08:34.531
And so it may be that the hard drive kinda dies out for day-to-day usage.

0:08:34.531,0:08:38.600
Like, we don't need it: we can just use these chips. So that remains to be seen.

0:08:38.600,0:08:41.833
So when you've got a hard drive or a flash chip

0:08:41.833,0:08:49.500
that just has this big area of bytes to do persistent storage, um, just on its own it's not really ready for the user to use.

0:08:49.500,0:08:54.825
Usually what happens is, the hard drive or flash drive is organised with what's called a file system.

0:08:54.825,0:08:59.400
And so the file system is just a way of organising this big area of bytes

0:08:59.400,0:09:04.700
and giving it that sort of familiar structure of files and folders.

0:09:04.700,0:09:07.178
And they each have names, and you can move them around and stuff.

0:09:07.178,0:09:16.791
And so a file is really just a way of taking some area of, you know, 100,000 bytes, and assigning a name to them.

0:09:16.791,0:09:20.667
So saying, 'look, this is flowers.jpg'. And flowers.jpg, that name, refers to those 100,000 bytes.

0:09:20.667,0:09:23.033
And then the user can copy it, or move it around, or whatever.

0:09:23.033,0:09:28.900
So, the file system just facilitates for you, seeing what data you have on there

0:09:28.900,0:09:31.800
and moving it around and organising it.

0:09:31.800,0:09:34.810
So that's our quick introduction.

0:09:34.810,0:09:36.900
So actually what I'd like to do is show you just pictures of actual hardware.

0:09:36.900,0:09:37.400
So, this is a picture of a motherboard.

0:09:37.400,0:09:41.100
This is a computer, a Shuttle computer, I bought in I think 2008, and then it broke.

0:09:41.100,0:09:47.800
So it became my little demo computer. [br]

0:09:47.800,0:09:52.318
So this was a cheap computer, about $200 with all[br]the parts.

0:09:52.318,0:09:56.358
So this is the motherboard all the electronic components plug into.

0:09:56.358,0:09:58.467
And right here in the middle is maybe the most important component. That's the CPU.

0:09:58.467,0:10:04.996
So let's zoom in on that.

0:10:04.996,0:10:10.733
So, if you kinda zoom in and look at the CPU, this metal[br]package has the CPU chip in it.

0:10:10.733,0:10:16.200
And I'm gonna flip it over. If you flip it over you see there's all these gold pads here.

0:10:16.200,0:10:20.633
So the CPU is the most complicated chip on here and so it has a very large number of connections,

0:10:20.633,0:10:22.933
electrical connections to the motherboard.

0:10:22.933,0:10:28.727
And so then I can look again at my Wikimedia image, and now you can appreciate...

0:10:28.727,0:10:34.000
...well, so there's these little tiny wires around the outside. So these connect to pads on the package

0:10:34.000,0:10:36.761
- the gold pads we were seeing -

0:10:36.761,0:10:41.033
and so inside the package they connect to little tiny spots[br]around the chip

0:10:41.033,0:10:43.200
in order to get the electricity into the transistors on the side[br]here.

0:10:43.200,0:10:49.667
The other thing I'll point out here is this copper thing. There's a second chip underneath here.

0:10:49.667,0:10:55.533
This is called a heatsink. So, the chip, because it has electricity running through it, it can heat up,

0:10:55.533,0:10:59.470
so there needs to be a way of dissipating that heat.

0:10:59.470,0:11:01.281
This is made of copper: copper's really good at[br]conducting heat,

0:11:01.281,0:11:06.715
and so just by bolting that on there, it keeps the chip cool enough to operate.

0:11:06.715,0:11:12.167
There used to be another heatsink on top of the CPU here, but I removed it. Just so I could take it apart and show it to you.

0:11:12.167,0:11:20.967
All righty. So that's the CPU in the, uh, in this computer. So now let's look at the RAM.

0:11:20.967,0:11:24.700
So if you look at the side of the computer here, this is the RAM.

0:11:24.700,0:11:31.100
It's on a little separate card. And[br]in this picture I have removed the card.

0:11:31.100,0:11:33.533
So the card fits into the slot here, so that's RAM.

0:11:33.533,0:11:38.712
So that's about 512 megabytes of RAM.

0:11:38.712,0:11:41.533
This is some years ago. You probably couldn't buy a RAM card that small nowadays.

0:11:41.533,0:11:47.767
So, you can see there's two chips here and there's two more chips underneath the stickers.

0:11:47.767,0:11:55.300
So this was made with four chips. Probably by Moore's Law, when this card was manufactured a few years before,

0:11:55.300,0:11:56.967
it probably used to be eight chips.

0:11:56.967,0:12:00.567
And then, by Moore's law, they can fit more under each chip and so they can just save money.

0:12:00.567,0:12:05.693
So, for the same 512 megabytes they could use fewer chips, so it's cheaper.

0:12:05.693,0:12:10.900
So that's...what do we have...CPU and RAM. So the last thing we need is persistent storage.

0:12:10.900,0:12:14.833
So, for this computer, persistent storage was provided by this. This is a hard drive.

0:12:14.833,0:12:19.000
So this is a three and a half inch hard drive - very typical size for a desktoop computer.

0:12:19.000,0:12:23.619
So this is where there's the spinning magnetic disk in here.

0:12:23.619,0:12:31.700
And this connects to the motherboard by this little SATA cable, which is a standard thing.

0:12:31.700,0:12:35.508
So those are the three parts of a computer.

0:12:35.508,0:12:36.767
That was a $200 computer, and it sorta did everything you'd want a computer to do.

0:12:36.767,0:12:43.900
More recently now we've got this alternative to the hard drive.

0:12:43.900,0:12:49.904
So this is a USB flash drive, or sometimes called a thumb drive.

0:12:49.904,0:12:54.367
So it's, you know, it's tiny. And I took this one apart.

0:12:54.367,0:12:59.471
And so if you look inside of it, this is a flash chip.

0:12:59.471,0:13:04.600
So this is the chip that just stores persistent data, little 0's and 1's, as little groups of electrons.

0:13:04.600,0:13:08.852
So this is the thing that's competing with the hard drive.

0:13:08.852,0:13:15.800
So this is a one gigabit chip, so it stores one billion bits.

0:13:15.800,0:13:22.644
And later on we'll look at how many bytes that might be. So that's a thumb drive.

0:13:22.644,0:13:27.520
This is an SD card, which is just a similar, you know, just an alternative to the thumb drive.

0:13:27.520,0:13:31.003
It's really just the same technology; it's just a different shape basically.

0:13:31.003,0:13:33.300
So this is the sort of thing you would use inside of a camera.

0:13:33.300,0:13:37.830
So as a last example, looking at that big[br]computer...

0:13:37.830,0:13:43.133
So, one of the effects of Moore's Law is that you get these cheap little computers that can sort of fit into different places.

0:13:43.133,0:13:48.465
So a little computer on a chip is known as a microcontroller.

0:13:48.465,0:13:49.933
So the idea is, that instead of having all these separate chips

0:13:49.933,0:13:56.963
you can fit the CPU, the RAM, and the persistent storage[br]all onto one chip.

0:13:56.963,0:14:03.883
And it's not gonna have a lot of power, but it's gonna be cheap. And Moore's Law has made that possible. [br]

0:14:03.883,0:14:07.970
So microcontrollers, now, you can buy essentially the whole computer for under a dollar,

0:14:07.970,0:14:12.033
and it's just on the one chip. So these are the kinda computers - or I should say microcontrollers -

0:14:12.033,0:14:13.821
that you would find in a thermostat,

0:14:13.821,0:14:18.133
or they're probably scattered around your car doing[br]little computer functions.

0:14:18.133,0:14:27.167
So, a neat example of a micro-controller is this[br]guy. This is an Arduino board.

0:14:27.167,0:14:33.167
And this is a free and open source board, just offered[br]by artists or hobbyists, or just for kinda playing around.

0:14:33.167,0:14:37.267
So this here. This is the chip; this is the micro controller.

0:14:37.267,0:14:40.867
So, it has a little bit of RAM, a little bit of CPU, and a little bit of persistent storage

0:14:40.867,0:14:45.300
just all on there. And then it's put on this board with some other support chips:[br]

0:14:45.300,0:14:50.000
so, this is a USB chip, and it's got some power chips here to just make the whole thing work.

0:14:50.000,0:14:54.167
So, you can buy a version of this I think for about $20.

0:14:54.167,0:14:56.333
And the idea is, it's just a little computer,

0:14:56.333,0:14:59.633
so it can read sensors or switches, or control little lights or whatever.

0:14:59.633,0:15:05.323
So it's just a fun way to play around and make, like, an[br]art project, or something like that.

0:15:05.323,0:15:06.000
So if you like working with your hands and[br]you like wires,

0:15:06.000,9:59:59.000
then this is another form of computer that might be good to play with.