Lesson video

Hello, my name's Mrs. Jones and I'm really pleased you decided to join this lesson today.

In this lesson, we will look at bits and bytes and how we convert from one to another, as well as the meaning behind the different prefixes.

We'll also look at how data is transferred across different digital devices.

So let's get started.

Welcome to today's lesson.

Today's lesson is called Measurements of data, from the unit, Data representation: text and numbers.

And by the end of this lesson, you will be able to provide examples of the different ways binary digits are physically represented in digital devices.

There are two keywords to today's lesson: Unit.

Unit is a standard measurement used to quantify the amount of digital information.

Prefix.

Prefix changes the size of the unit by a certain amount.

There are three sections to today's lesson.

The first, Convert between bits and bytes.

Second, Express sizes using prefixes, and the third, Explain how data is transferred.

So let's start with Convert between bits and bytes.

We use nanometers to measure the size of molecules.

We use centimetres to measure the size of objects.

We use kilometres to measure the distance between cities.

And Lucas asks, "Why do we use different units?" Different units are best suited for different contexts.

Kilometres are useful for measuring long distances.

Centimetres and millimetres are better for smaller objects.

Nanometers are used to measure extremely small things on the scale of atoms and molecules.

You could say 0.

000000002 metres instead of two nanometers.

But that's hard to read, easy to make mistakes with and impractical for quick communication.

In computing, it's very common to group binary digits into chunks of eight.

A group of eight binary digits is called a byte.

Caution though: A bit is one binary digit.

A byte is eight binary digits.

These are not the same and do not confuse them.

For example, here are eight binary digits.

This is a byte.

This is one byte.

Eight binary digits together is one byte.

Here are 24 binary digits.

This is three bytes.

There are three sets of eight binary digits, which means there are three bytes.

This is a sequence of 128 bits.

What size is it in bytes? Or how many groups of eight can you form with 128 bits? 128 divided by 8 equals 16 bytes, and we can write that as 16 bytes or 16 capital B.

Let's have a quick check.

A group of eight binary digits is called a.

A: bit? B: nibble? C: byte? Pause the video to consider your answer and then we'll check it.

Let's check your answer.

The answer was C, a byte.

Well done if you got that correct.

To convert bits to bytes, divide the number of bits by eight because this is how many groups of eight bits, for example, bytes, fit in the sequence.

So to go from bits to bytes, we divide by eight.

To convert bytes to bits, we multiply the number of bytes by eight because there are eight bits in every byte.

Bytes to bits, multiply by eight.

Let's have a quick check.

A piece of text is 16 bytes long.

What is its size in bits? Pause the video, go back through the slides, consider your answer and then we'll check it.

Let's check your answer.

There are 16 groups of eight bits, 16 x 8 equals 128 bits, which can also be written as 128 lowercase b.

Well done if you got that correct.

Let's do an activity.

A user comes across a small text file in her hard disc.

The name of the file is simple and its size is 12 bytes.

How many binary digits, bits, does this file contain? Pause the video, go back through the slides, use your worksheet and then we'll check your answer.

Let's check your answer.

There are eight bits in a byte, so there are 8 multiplied by 12 because we've got 12 bytes.

So it is 96 bits in the file.

Well done if you got that correct.

Let's do the second part of the activity.

The table below contains examples of a few symbols and their binary encodings in the UTF-8 coding scheme.

Fill in the last column of the table to state how many bytes are required for each of the characters.

So you can see there the table, you have the characters on the left.

The next column has the binary representation.

The next column has the number of bits.

And you need to complete the number of bytes.

Pause the video, go back through the slides, use your worksheet and then we'll check your answers.

Let's check your answers.

The answers for the first one, which was the @ character was 8 divided by 8 equals one byte.

For the pound sign we had 16 bits.

16 divided by 8 is 2 bytes.

The next character where we have those three flower star symbols characters there, is 24 bits.

24 divided by 8 was 3 bytes.

And for the musical note, we had 32 number of bits, 32 divided by 8 equals 4 bytes.

Well done if you got those correct.

Let's move to the second part of today's lesson: Express sizes using prefixes.

True or false? Binary digits can only be used to represent characters and numbers.

Pause the video to consider if that is true or false and then we'll check your answers.

Let's check your answer.

The answer is false.

All pieces of information are represented as sequences of binary digits.

Well done if you got that correct.

All pieces of information are represented as sequences of binary digits.

For example, text, numbers, images, sounds, animations, and videos, programmes.

Sequences of binary digits tend to get really long.

A type of information here is a chapter in a book.

The number of bits is a few thousand.

A photograph or a song is a few million bits.

A film, the human genome is a few billion bits.

All the files on a computer or all the files on Wikipedia is a few trillion bits.

How do we talk about these huge numbers of binary digits? Scientists use prefixes to denote multiples of a unit.

The prefix kilo or k for short is a thousands.

Mega, in short a capital M, means millions.

Giga, capital G, means billions.

Tera, capital T, is trillions.

We use multiples such as thousands, millions, et cetera, and that's what we use.

So for example, 3000 grammes is three kilogrammes or 3 lowercase kg.

8 million pixels is eight megapixels or 8, capitals, MP.

4.

5 billion years is 4.

5 gigayears.

Let's have a quick check.

Can you put the prefixes here into order from smallest to largest? So you have A: tera, B: kilo, C: giga, D: mega.

What order should those be in to go from smallest to largest? Pause the video to consider your answer and then we'll check it.

Let's check your answer.

The answer is B: kilo, D: mega, C: giga, and then A: tera.

Well done if you got that order correct.

Izzy says, "My favourite song is 24 million bits." It is common practise to use prefixes instead of multiples.

For example, replace millions with mega.

So then Izzy would say, "My favourite song is 24 megabits." Use short forms. For example, replace mega with a capital M and bits with a lowercase B.

So now Izzy would say, my favourite song is 24 megabits, or 24, capital M, lowercase b." Convert bits to bytes and use an uppercase B for bytes.

So now she would say, "My favourite song is three megabytes or 3, capital M, capital B.

So a sequence that is 24 million binary digits long would be described as 3MB, three megabytes.

Let's have a look at another example.

Aisha says, "My operating system is two gigabytes." 2, capital G, capital B.

Expand short forms, for example, use giga and bytes instead of G and B.

So now Aisha says, "My operating system is 2, capital G, capital B or 2 gigabytes." Translate prefixes to multiples, for example, billions instead of giga.

So now Aisha says, "My operating system is 2 billion bytes." Convert bytes to bits if needed.

And now Aisha says "My operating system is 16 billion bits." So when we say something is two gigabytes in size, we really mean that it's a sequence of 16 billion binary digits.

Translating and converting will help you interpret what many seem like gibberish.

Let's do an activity.

Use your worksheet for this.

You've been provided with the name, size, and type of six files.

Put the files in order of size from smallest to largest.

Pause the video, go back through the slides, use your worksheet and then we'll check it.

Let's check your answers.

So the order we have is the logo, which was an image which is 23kB book.

txt, which is a text file, which is 720kB, a song which is audio, 1.

6MB a picture, image, 2.

3MB a book, which is a document, 23.

0MB and party, which is a video, is 2.

0GB.

Well done if you got those correct.

Let's do the second part of the activity.

A standard hard disc has a capacity of one terabyte.

T stands for the prefix tera and uppercase B means bytes.

So one TB is one terabyte.

There are two parts to this activity.

A: How many bytes is one terabyte? B: How many bits is one terabyte? And there's a hint at the bottom there.

Start from the answer to the previous question.

Pause the video, use your worksheet, and then we'll check your answers.

Let's check your answer.

So the first part was how many bytes is in one terabyte? Well, one terabyte is 1 trillion bytes.

The second part was how many bits in one terabyte? So 1 trillion bytes equals 1 trillion groups of eight bits, which means 8 trillion bits.

Well done if you got that correct.

Let's do the third part of this activity.

You really enjoy taking pictures with your mobile phone.

You purchase a 16 gigabyte memory card and you want to know how many pictures you can store on the memory card.

The size of each individual picture is approximately four megabytes.

A: The card's capacity is expressed in gigabytes.

A picture's size is expressed in megabytes.

You will need to convert how many megabytes is 16 gigabytes.

And the second part is how many pictures can be stored on your memory card? Pause the video, use your worksheet, go back through the slides and consider your answers and then we'll check them.

Let's check your answers.

The first part was the card's capacity is expressed in gigabytes, a picture size in megabytes, and you needed to convert how many megabytes is there in 16 gigabytes? One gigabyte is a thousand megabytes, so 16 gigabytes is 16,000 megabytes.

The second part was how many pictures can be stored on your memory card? So now that we know the megabytes, 16,000 divided by 4 equals 4,000 pictures.

Well done if you got those correct.

Let's move to the last part of today's lesson.

Explain how data is transferred.

In the past, programmes and data were stored and processed using perforated paper.

Zeros and ones were represented by the presence or lack of holes in the paper.

Magnetic core memory used metal rings connected with wires to store and process data.

Each ring, core, stored one bit.

Electricity was used for writing and reading the information in the cores.

Zeros and ones were represented by the way in which each core was magnetised.

Now computing devices use electronic components such as processors, main memory and storage devices.

In electronic components, zeros and ones are represented by the flow of electricity, controlled by interconnected switches.

Let's have a quick check.

What do electronic circuits use to represent and process binary digits? A: sound? B: light? C: electricity? D: magnetism? Pause the video to consider your answer and then we'll check it.

Let's check your answer.

The answer was C, electricity.

Well done if you got that correct.

Magnetic hard disc drives, HDDs or just hard drives, are used to store data.

The material on the surface of hard discs is magnetic.

Zeros and ones are represented as changes in the magnetic orientation, north-south, or south-north of individual regions of the surface.

The typical capacity of a hard disc is one terabyte, which is 8 trillion binary digits.

Solid state storage devices, SSDs, are a form of flash memory.

SSDs have no moving parts and can either be housed inside a computer system or used as an external device.

SSDs electronically store data in NAND flash memory cells.

Optical discs like CDs, DVDs, and Blu-ray discs store data so it can be transferred easily.

The surface of optical discs is reflective.

Zeros and ones are represented by pits, microscopic holes, or lands, regions without holes.

Light is used to read the binary digits off the surface of the disc.

The typical capacity of a CD is 700 megabytes, which equals 5.

6 billion binary digits.

Let's have a quick check.

What do hard disc drives, HDDs, use to represent and process binary digits? A: sound? B: light? C: electricity? D: magnetism? Pause the video to consider your answer and then we'll check it.

Let's check your answer.

The answer was D, magnetism.

Well done if you got that correct, Sam says, "But how are binary digits transmitted between digital devices?" Good question.

Binary digits are transmitted between devices either through wired or wireless connections.

Wired connections, binary digits are transferred through wires using electricity.

Binary digits are transferred through fibre optic cables using light.

You can see the image here of an ethernet cable at the top and the fibre optic cables at the bottom.

Wireless connections.

In all wireless communications, binary digits are transferred using electromagnetic waves transmitted and received by antennas.

Let's do an activity and you'll need your worksheet.

There are two parts.

The first, explain how data is stored on optical discs.

Second, explain how data is transferred from one digital device to another.

Pause the video, go back through the slides, use your worksheet and then we'll check your answers.

Let's check your answers.

For the first part, explain how data is stored on optical discs.

Data is stored on optical discs like CDs and DVDs using light.

Tiny marks called pits and lands are made on the surface of the disc.

Light is used to read the marks on the disc, which are read as zeros and ones.

The second part was explained how data is transferred from one digital device to another.

Data can be sent from one device to another using wires or wirelessly.

Wired waves use electricity or light to transmit data, and wireless waves use electromagnetic waves.

Well done if you've got those correct.

In summary, data is measured in units like bits and bytes, kilobytes, megabytes, and gigabytes.

You can convert between units.

Binary digits are physically represented in digital devices.

All digital data, whether text, images or videos, is stored using patterns of bits.

Well done for completing this lesson, Measurements of data.