Lesson video

Hi there, I'm Sara I'm your computing teacher for this unit representations.

This is lesson five of six, large quantities.

You will need a pen and you'll also need paper.

So pause the video, get pen and paper.

And when you finished unpause, but before that, don't forget to remove all notifications also and any other distractions, see you when you're ready.

In this lesson, you will understand the meaning of bytes.

Learn what the prefix is kilo-, mega-, giga-, and tera- mean practise converting between units.

In this lesson, you will understand the meaning of bytes.

Learn what the prefix is, kilo- mega- giga- and tera- mean and practise converting between units.

So here's a question for you, why measure? We use nanometers to measure the size of molecules, centimetres to size of objects and kilometres the distances between cities or towns.

Why then do we use different units of measurements? Think about that.

Pause the video and continue when you've had a good thought.

Why measure? Measurements required tools and provide scientists with a quantity.

A quantity tells a scientist how much of something there is and how many there are.

Scientists on the other hand use units to describe how something is measured and use different units to measure different things.

For instance, kilogramme for mass, seconds for time and so on.

A common measurement system allows us to make direct comparisons, for instance, no good saying 10 eggs weighs as much two apples.

What does that mean? Using different units and prefixes, however is not specific to computing, but common to all scientific practise.

Now, in this lesson, you will see how units for measuring the size of binary representations are used.

Time to explore units of measurement in computing bits and bytes.

And computing, it's quite common to group binary digits into chunks of eight.

A group of eight binary digit is called a byte, but you've got to be really careful because a bit it's one binary digit, which can be a zero or one and a bit it's is a smallest unit of in computing.

A byte however, is a group of eight bits and a byte is denoted using uppercase B and a bit lower case or bits lower case b.

So here are eight binary digits.

So what's that called? You've just seen in blue there, the definition, a definition, so what's that called? Do you think, what would that be? That's correct, this is one byte.

Now, since you're getting really good at this, here are 24 binary digits.

Now remember a group of eight binary digits it's called a byte.

So what would that be? How many bytes? That's correct, again, three bytes, because you can get three, lots of eight.

So all you do is divide 24 by eight and you get three bytes.

So remember bytes, is denoted using capital letters B and bits denoted using small upper case, lower case, rather b, right.

Now here before you are 128 bits all together, what is the size in bytes? So going back to the very last example you saw what you think the size in bytes is? Again, well done, correct.

So it just means how many groups of eight can you form with 128 bits? And when you divide 128 by eight, you get 16 bytes.

So it's 16 uppercase case B denoting bytes, So converting bits to bytes, here is a visual aid to help you remember what to do.

So you're converting bits to bytes so going from a smaller size unit, so to speak to a larger size unit.

And what you normally do is divide by eight because this is how many groups of eight bits would fit into that sequence, whatever sequence or number of bits given.

So converting bits to bytes.

Now here's another one for you.

So now, you're looking at this, from the other perspective, you have a piece of text 16 bytes long.

So you know that there are 16 groups of eight bits.

What is the size in bit? Again correct, so you've got the 16 groups now going, doing the opposite of what you've just done.

So you will multiply 16 by eight, and that will give you 128 bits.

And remember the bits is in lower case.

So bits lowercase b.

Right, again, using this visual aid to help you when converting from bytes to bits.

So you're going, if we could use that expression from a bigger sized unit to smaller sized units, you will be more supplying by eight.

So going the other way from bytes to bits, you will multiply by eight.

So again, just a reminder before you go onto your worksheet to get some vital practise, here is a visual aid to help you.

So from bits to bytes, you divide it by eight and from bytes to bits, you multiply by eight and don't forget a bit it's just one binary digit, and it's the smallest unit in computing and a byte on the other hand, it's a group of eight bits.

So pause the video and access your task one, you can either write on your worksheet or you can use your paper to work this out when you have finished and completed this task, just play to continue, right? Well done, well done for having a go.

So in the question you were given, you had a simple file called simple, and it's the size of the file is 12 bytes is a text file.

And the question asked you how many binary digits or bit does the file contain? So using your conversion diagram, that help you, you're converting from bytes to bits from the bigger units, a smaller unit.

So you'd have to multiply, remember bytes group of eight.

So you multiply by eight to get 96, and that's your answer.

Time for some more practise.

In this task, you need to complete the last column on the given table.

You need to find out how many bytes required for each character or symbol that has been provided on that table.

So have a go.

And when you've completed, just play to continue.

Right, well done.

So you've got here character symbols.

You've got that at sign.

You've got the pound sign and the binary representation is given on the next or second column.

So the first example, you've got eight bits and you've actually been given the number of bits.

It's been counted for you.

So don't forget using your conversion diagram.

You need a number of bytes.

So you're going from bits to bytes.

And when you're going from bits to bytes, you need to divide.

So in the first example, we'll divide eight by eight to get one byte, and you do the same for all the other symbols to get your answer.

So check your answer and continue pause for a bit to check your answer.

You can continue once you're done that.

In summary, then every piece of data found on the computer is represented as a series of binary digits.

Zeroes and ones bits.

So it doesn't matter whether or not it's a text file or an image file, or sound file, an animation.

Everything stored are sequences of bits.

Computing devices have the capacity to store enormous amount of data.

So sequences of binary digits health can soon get really long.

Take a look of what we mean by that.

The chapter in a book for instance, can hold a few thousand bits, a song or photograph, a few million bits, a film can be a few billion and say all the files on a computer, all the files in Wikimedia for instance can take or hold of a few trillion, or how do we describe these long sequences of data? Now here before you Pico and Giga are having a conversation.

And Giga is saying to Pico up my favourite song is 24,354,768 bits, that's a mouthful.

We don't normally talking that much detail.

What we would normally do is talk or use multiple to describe what we mean like millions.

So the prefixes using computing, you saw earlier that scientists do use prefixes to denote multiples of units.

The prefixes used are kilo- for thousands, mega- for millions giga- billions and tera- trillions, and the short form notation used are K, M, G and T.

For example, 3000 grammes is three kilogrammes or three kg.

Right, so let's look how prefixes can be used with bytes and bits.

So Giga is saying to Pico here.

My favourite song is 24 million bits.

Phew, so that's replace that long number we saw earlier.

So it's common practise to to actually speak this way, but instead we can use multiples such as mega to replace millions to say, or describe what we mean.

So Pico can say for instance, 24 megabits instead, now that can be further shortened by use of the short form M and lowercase b for bits.

So it can become 24Mb that's even shorter.

To convert the, the bits to bytes, just replace the lower case b with uppercase B.

And that will be three megabyte and Pico is rather impressed by that, right? So the size of a sequence, which is 24 million binary digits long can be described as three MB.

Can you see why? That's correct.

So that's bits, binary digits, and what's been described here is in bytes.

So what's happened is bits converted to bytes, make three, you know there are eight groups of eight bits in a byte.

So to go from a smaller size unit to your larger size unit, you will be dividing.

So 24 divided by eight is three, and the million is mega.

And the short form is M and B for bytes, because it has just been converted.

To really understand how to describe sizes, let's try the other way too, right? Pico this time is saying my operating system is two GB.

Now you can expand GB for short form and use prefixes.

The prefixes you saw earlier, you will remember that G stands for giga and B stands for bytes.

So easily Pico could have said two gigabytes.

Now what comes next? Yes, you can also expand even further by using multiples.

You saw how we use multiples to describe sizes.

So instead of gigabytes, Pico can say my operating system is two billion bytes and also Pico can convert byte to bit.

And all Pico needs to do is just convert it, and it becomes 16 billion bits.

Now you remember that eight bits make a byte.

So all Pico going back again, all Pico had to do was just multiply two by eight.

And that converts bytes to bits and Pico can say my operating system is 16 billion bits, and that really impressed Giga.

Cause you could see the expression on Giga face, like wow.

So Pico can now say that his operating system or her operating system is 16 billion binary digits.

So that's how you can describe sizes, really, really long sequences of bits.

Now it's time for you to have a go at more practise so you can find your way around units and prefixes.

But before you do that, you have been provided with a help sheet.

This sheet summarises all the definitions and helps you find your way around conversions.

So you can easily carry out the conversions with the visual aid provided.

In task three, you will be comparing between sizes to start with all you need doing this task is order the sizes you've been given from smallest to largest in ascending order.

And by all means pause the video.

And when you have completed the task, just play to continue.

So here's the answer.

The smallest size would be 23 kilobytes ranging all the way up to two gigabytes.

So take a look and check your answer.

More practise, this will help refine all you've learned and the skills you've learned.

In this particular task, task four, read the question in the worksheet and complete pause the video by all means.

And when you've completed this task unpause to continue well done, so let's go through the solution together.

So how many bytes is one terabyte? So to get the answer, you've got to work logically.

So you know the number of bytes in one terabytes, so tera- you need to kind of describe or expand it.

So you're going to expand that notation.

What does tera- mean? Tera- means trillion.

So you're not using the prefixes.

You're interpreting the prefects.

So all you need to do is replace tera- with trillion we want trillion bytes.

So one terabyte is one trillion bytes.

So the next tech now is how many bits is one terabyte.

So you've got bits and you've got bytes.

So that's the first hint.

So the number of bits in one terabyte, how did we get eight million bits? We're working from a smaller unit to a large sized unit.

So you're converting from bits to bytes and you know, there are eight bits that make a byte.

So all you need to do is one times eight will be eight and you replace your bytes with bits, you've just converted it.

So it'll be eight trillion bits will be your answer.

So some more practise really embed that knowledge and the skill you've just learned.

So have a go at this one, how many will fit? Read the question in the worksheet and complete.

You can also use your notepad and if you're not using your worksheet, so that's fine also.

Don't forget to use a cheat sheet, to look at the definitions and see how to make the conversions using the diagrams given on the cheat sheet.

So pause the video and when you've completed this task, just unpause to continue.

Well done for having a good go.

So let's go through this one.

You really enjoy taking pictures with your mobile phone.

So you purchase a 16 gigabyte memory card, and you want to know how many pictures you can store on your memory card.

So the average size of a picture is approximately four megabytes.

So the first thing you notice here is that you've got a mismatch of units.

So you've got to convert to make sure the units match.

You've got 16 gigabytes and you've got four megabytes.

So you need to convert first because you know, 1000 megabytes make one gigabyte.

You will multiply 16 by thousand to convert your gigabytes to megabytes.

So you've got 16,000 megabytes capacity on your memory card.

So the next step will be now to find out how many of those four megabyte pictures will fit in your memory card.

That's just going to be a simple case of dividing by four, because you want to know how many four bits fit in.

And when you do that calculation, you arrive at 4,000.

So 4,000 pictures will fit Well done, you've come to the end of this lesson and you have gained really vital skills.

And you now know how to describe really long sequences of bits.

Now you have seen that all pieces of information I've represented as sequences of binary digits or bits.

So it doesn't matter whether it's a sound or text or animation images.

Everything is represented as sequences of bits and you know that to handle or describe this very long sequences of bit, prefixes can be used when we describe these sizes.

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Hope to see you next lesson.