Lesson video

Hi, I'm Rebecca, your computing teacher for the Data Representations unit.

And this is your final lesson in this unit.

For this lesson, you're going to need your pen and paper so that you can make notes and do any calculations that you need to.

You're also going to need to remove as many distractions as you possibly can out of the way so that you can really focus in this lesson.

Once you've done all that, we can begin.

In this lesson, you will define the terms bit, nibble, byte, megabyte, gigabyte, terabytes, and petabyte.

And you'll be able to convert between units of measurement.

What I'd like you to do then is to place these units of measurement in order from smallest to largest.

Pause your video while you do that.

Awesome, so, here's the answer.

So, what I did is I converted each one to bits so that I could see the actual order 'cause I found that a little bit easier to do.

So one byte has eight bits, three nibbles has got 12 bits, and then you've got your 16 bits.

So then you can sort it into order based on their bits.

Now the smallest unit of measurement is a single bit, and you're also familiar with nibbles and bytes because we've been looking at those throughout this whole unit.

Here are some other units of measurement.

So you've got a kilobyte, a megabyte, a gigabyte, a terabyte, and a petabyte.

And if you look at that conversion on the right-hand side, a kilobyte is a thousand bytes.

A megabyte is a thousand kilobytes.

A gigabyte is a thousand megabytes.

So each one goes up in those thousands each time.

So it's just a pattern that you need to remember when you're thinking about your conversions.

So it's really important that you know the order in which those units of measurements come in.

So what I want you to do is think of a silly sentence to do those units of measurement to come up with it so that you remember the order that they come in.

So you've got bit, nibble, byte, kilobyte, megabyte, gigabyte, terabyte, petabyte.

What are you going to do, what silly sentence can you do to make you remember the order? Now it's a little bit like when I was at school and I learned about the planets and the order for the planets, I made a silly sentence, which was My very early morning jam sandwich usually nauseates people.

And that was when Pluto was still classed as a planet, that's why I got P at the end.

And that always, for my whole life since I learned that, I can remember the order of the planets from that.

So what I want to do you to do is come up with a silly sentence just like that, but for these units of measurements instead.

So pause your video while you have a think about that.

So here's the one that I came up with.

So be nice Barry, Kumar makes gorgeous tomato pizzas.

So if you can remember that silly sentence, then you'll be able to remember that the beginning letter of each of those words corresponds to one of these words that is in these units of measurements.

So hopefully having a silly sentence there will help you remember the order because that order is so important if you're asked to convert those units of measurement, say from gigabytes to megabytes, for example.

you need to know where it is in that list and where you, whether you've got to multiply it by a thousand or, if you were doing eight bits, whether you got to multiply it by eight, you need to know that order so that you can figure it out.

So, which of these is the largest? And use your silly sentence to help you.

Which of these is the largest? It's the petabyte.

Which of these is the smallest? It's the kilobyte.

Which of these is the smallest? It's a tricky one, this is it involves, a tiny bit of math thinking about it in your head.

Let's take a look.

It's actually one megabyte, and that is because 2 million bytes is actually two megabytes.

So that 2 million bytes is actually larger than one megabyte.

So you'd need to convert that in your head to work out the correct answer.

So converting between units of measurements, let's have a go at some.

So two numbers that you really need to remember for your conversions are 1,000 and eight.

So things like there are a thousand bytes in a kilobyte, you remember each one goes up by a thousand each time in that order.

And also there are eight bits in a byte.

So when you get to those really small numbers, so the bits, you're going to need to make sure that you remember that eight, because there are eight bits in bytes, so you might have to divide by eight, you might have to multiply by eight.

But as long as you remember those two numbers, you're going to be all right.

So it's not always a thousand, and it's not always eight, but you got to know when to use eight and when to use a thousand.

So here is a typical question.

Convert 50 bites to into bits.

There are eight bits in a byte, so we need to do the following calculation.

So we need to do 50 times eight.

So if you want to do that in your head, you could just do five times eight and add the zero.

And that's going to give you, 400 bits.

So let's try another then.

Convert 3000 kilobytes to megabytes.

So you've got to think about the order.

So it goes kilobytes then it goes megabytes.

So it's going to be less megabytes than it is kilobytes.

So you've got to do some division there.

So there are thousand kilobytes in a megabyte.

So we need to do the following calculation.

So 3000 divided by 1000, let's take a look.

So it's just three megabytes.

Let's try another then.

Convert 40,000 bits into kilobytes.

So this is slightly trickier 'cause it's got some extra steps.

There are eight bits in a byte.

Remember that number eight that we've got to remember, and there are 1,000 bytes in a kilobyte.

So we've got to do two steps this time.

So we do 40,000 divided by eight to get the number of bytes.

And then whatever that answer is, we divide by 1,000 to get the number of kilobytes.

So let's look at what the answers would be.

So 40,000 divided by eight is 5,000.

And then 5,000 bytes divided by 1,000 gives us five kilobytes.

So let's quick recap back to our representing sound lesson.

Here is a typical question.

So it says, calculate the file size in bytes for a one minute sound recording that has used a sample rate of 1,000 Hertz and a sample rev resolution of four bits.

Now, where we've done this before, we've worked it out in bits only.

We haven't worked it out in bytes.

So let's see the difference.

So, let's do the answering bits first 'cause that's what we know how to do.

So 1,000 Hertz times four bits times 60 seconds, and that gives us 240,000 bits.

But now we convert it to bytes.

So what do we need to divide by in order to work out the bytes? We need to divide by eight.

So 240,000 divided by eight, and you can do that the 24 divided by eight to cheat a little bit, to help you with that.

And it's 30,000 bytes.

So what if the question said kilobytes instead? Then you've got to do a little bit of a further step.

So, exactly the same question, but instead of saying, file size in bytes, it's now saying file size in kilobytes.

So now we've got to do an extra step on top of that.

So what's the extra step? We need to also divide it by 1,000.

So we can work it out now that it's 30 kilobytes.

So 240,000 bits is 30,000 bytes and is 30 kilobytes.

So, really important is remembering that order.

Be nice Barry, Kumar makes gorgeous tomato pizzas.

As long as you remember the order, you should be able to work out which calculation you need to perform.

Now in your quiz at the end, you'll be given some more to help practise that further.

That's the end of this unit, and it's been a whistle stop tour of data representation.

I hope you've enjoyed it.

I hope you haven't found it too challenging.

There's lots of maths that goes on in this, but hopefully I've made it simple enough for you to carry on when you're working independently by yourself.

So, if anything has, found, if you found anything a little bit struggling over this unit, then please revisit those lessons and just practise them more and more and more.

And that's the important thing with any of these things where there's lots of formulas to remember, lots of calculations to remember.

It's just repetition to get your brain remembering all of those things, so anything that you're not sure about now, just go back to that lesson and recap it and try the quiz and see if you do better.

And you can even start making up your own questions as well.

That would be a good thing to take yourself a little bit further.

So, hopefully I'll see you again for another unit.