Lesson video

Hello.

My name is Mrs Holbrow, and welcome to computing.

I'm so pleased that you've decided to join me for the lesson today.

In today's lesson, we're going to be exploring binary numbers, and we're going to investigate why computers use binary.

Welcome to today's lesson from the unit, Representation of Numbers.

This lesson is called, Why Do Computers Use Binary? And by the end of today's lesson, you'll be able to explain why computers use binary to represent all data and instructions.

Shall we make a start? We will be exploring these keywords during today's lesson.

Data.

Data.

Raw facts such as numbers or text presented without any meaning.

Binary.

Binary.

A number system that uses the digits zero and one to represent data.

Instructions.

Instructions.

Directions on how to carry out a specific task.

Transistor.

Transistor.

A tiny electronic switch controlled by electricity.

There are two main parts to today's lesson.

We'll start by recognising why computers use binary, and then we'll move on to explain how binary relates to electrical signals.

Let's make a start by recognising why computers use binary.

This clay tablet is on display in the British Museum and dates back to Egyptian times.

Why is the invention of writing so important? Perhaps pause your video here and have a think.

The invention of writing is important because messages can be transmitted across long distances.

Messages can be stored for long periods of time.

If you transmit a message verbally, the person you speak to has to remember that message.

You can also communicate with many people, and you can share knowledge.

Did you have any other reasons why the invention of writing is so important? Writing is just a means of representing data.

There can be many different ways of representing the same thing.

This image shows a comparison of early Cuneiform, Egyptian, and Chinese characters.

Alex looks a bit confused.

He says, "How is it possible for a shape to represent a word?" Laura's got a great response.

Laura says, "Everyone has to agree on it." This means if we use a shape or image to represent a word, then everybody needs to know what that shape or image represents.

We use computers for a huge range of things.

But how does a computer represent a picture, your score in a game, the song that you listen to on your phone, or that online video that you watched last night? All data that is processed or stored in a computer is in binary format.

But why? Binary is a number system that uses the digits zero and one to represent data.

Everything stored on a computer is represented by sequences of ones and zeros.

101011001 is an example of some binary data.

This data could be a number or a letter, or it could be a tiny part of an image.

The computer interprets it to give it meaning.

Time to check your understanding.

Binary is a number system that consists of ones and twos to represent data.

Is this statement true or false? Pause the video here whilst you have a think.

How did you get on? The correct answer is false.

And it's false because binary is a number system that uses the digits zero and one to represent data, not ones and twos.

Computers don't just use binary to store data.

They use binary to store instructions too.

What is an instruction? An instruction is a direction on how to carry out a specific task.

For example, in this calculation, five multiplied by 12.

Five and 12 are the data.

X is a symbol that means multiply.

The instruction is to multiply five by 12.

Time for a check.

Fill in the blanks to complete the sentence.

Computers don't just use binary to store data.

They use to store too.

Pause the video here whilst you complete the task.

How did you get on? Did you correctly complete the sentence? Let's have a look at the answers together.

Computers don't just use binary to store data.

They use binary to store instructions too.

Instructions are information on how to carry out a specific task.

Computer programmes consist of thousands of instructions.

These are all stored as binary in your computer.

Aisha says, "Wait, even my online game is made up of ones and zeros?" Alex says, "Yes, and this social media app on my phone, binary is everywhere!" You're doing a fantastic job so far.

So well done.

We're now going to move on to the first set of tasks for today's lesson, task A.

I'd like you to have a look at these statements.

All of these statements are currently false.

You need to spot the errors and write the correct version of each statement and write it down in the right hand column of the table.

Pause the video here whilst you complete the activity.

How did you get on? You're doing a great job so well done.

Let's have a look at some sample answers together.

So I've broken the table down into sections just so we can see it a bit more clearly.

The first statement that was incorrect was data is the only thing that is stored as binary on computers.

The corrected version is both data and instructions are stored as binary on computers.

The next incorrect statement was sequences of ones and zeros on their own are meaningful.

The corrected statement is sequences of ones and zeros represent data but have no meaning until interpreted by a computer.

And the last one on this slide, only some data on a computer is stored as binary.

The corrected version is all data on a computer is stored as binary.

Let's have a look at the final two.

So the incorrect statement was binary is a number system that consists of the numbers from zero to nine.

The corrected statement is binary is a number system that consists of the numbers zero and one.

And the final one, only numbers can be represented by binary when stored on a computer.

The corrected statement for this is all types of data.

So for example, numbers, characters, images, sound, and video can be represented by binary when stored on a computer.

Remember, if you need to go back and make any corrections or add any extra detail to your answers, you can pause your video here and do that now.

We're now moving on to the second part of today's lesson, where we're going to explain how binary relates to electrical signals.

Computers are made of electrical circuits.

The wires in the circuits can have a high voltage, which is on, or low voltage, which is off.

These signals within a computer circuit can be changed or set by transistors.

So you can see here an image of a motherboard.

And if you look very closely, you can see the tiny little electrical circuits which are printed onto the board.

Imagine a long string of light bulbs.

Each bulb can be either on, represented by a one, or off, which is represented by a zero.

By arranging the on-off patterns of the bulbs, you can represent different pieces of data.

Time to check your understanding.

In an electrical circuit inside a computer, what binary state does high voltage represent? Is it A, zero, B, one, or C, two? Pause the video here whilst you have a think.

How did you get on? Did you select one? Great work.

In an electrical circuit inside a computer, the binary state one represents high voltage.

How many different states can one light bulb be in? Maybe pause the video here and have a think.

Ah, Laura's got a response.

Laura says, "Two: on or off." Well done, Laura.

That's correct.

These two states could also be called true or false, or one and zero.

Time to do a quick check of your understanding.

Which state could a light bulb not be in? A, on, B, off, or C, a bulb that is half on? Pause the video here whilst you have a think.

That's right.

A bulb can't be half on and half off.

The more light bulbs you have, the more things you can represent.

Alex has a question.

How many different combinations can you make with a group of two light bulbs? Maybe pause the video here and have a quick think.

Jun's got an excellent response.

Jun says you can make four different combinations of on and off with just two bulbs.

Let's have a look what that looks like.

Both bulbs could be off, zero, zero.

One bulb could be on and the other one could be off, one, zero.

And then we could swap that around, so we could have zero, one.

And then finally, both bulbs can be on, so one, one.

Although in a computer, we don't have lots of tiny little bulbs.

In a computer, transistors are used instead of bulbs.

Transistors are tiny electronic switches.

These switches can either be on or off, with on representing one and off representing zero.

These ones and zeros are the basis of binary.

A series of transistors can store a sequence of ones and zeros, which can represent a piece of data.

This image shows a series of switches, which could represent one, 10101110 in binary.

Okay, you're doing a great job, so well done.

We're now going to move on to the second set of tasks for today's lesson, task B.

I'd like you to start by working out how many different combinations of on-off light bulbs you can have with three light bulbs? Fill in the table's rows with each combination.

Use a one to represent on and a zero to represent off.

The first row has been done for you.

Pause the video here whilst you complete the activity.

How did you get on? Great work.

There are eight different combinations when you have three bulbs.

So hopefully you filled in your table to look something like this.

The order of your rows doesn't have to match mine exactly, as long as you've looked at each possible combination correctly.

So the first row was done for us, zero, zero, zero.

The second row, the last bulb could be on, so zero, zero, one.

Second row, the middle bulb could be on, zero, one, zero.

Next, we could have both two and three bulbs on, so zero, one, one.

The first bulb could be on, so one, zero, zero.

The first and the third bulb could be on, so one, zero, one.

The first and second bulbs could be on, one, one, zero.

And then finally, all bulbs could be on, so one, one, one.

For the next part, I'd like you to work out how many combinations of on, off light bulbs you can have with four light bulbs this time.

Fill in the tables rows with each combination.

Remember, use a one to represent on and zero to represent off.

The first row has been done for you, and you may need to add more rows to the table as needed.

Pause the video here whilst you complete the activity.

How did you get on? Great work.

Hopefully, you identified that there are 16 different combinations of four light bulbs, and you can see here I've completed my table with each of those combinations.

Remember, if you've done your table in a slightly different order, it doesn't matter.

Finally, use the knowledge you've gained from completing questions one and two.

How many possible combinations do you think there would be if we had five bulbs or six bulbs? What is the pattern? Pause the video here whilst you have a think.

Did you spot the pattern? Well done.

So for A, if we have five bulbs, there are 32 possible combinations, and for B, if we have six bulbs, there are 64 possible combinations.

And hopefully, you spotted the pattern that they double each time.

So with two bulbs, we had four possible combinations.

With three bulbs, we had eight possible combinations, and so on.

You've done a fantastic job in today's lesson.

Let's summarise what we have learnt.

Computers store all data and instructions as binary.

Binary is a number system consisting of ones and zeros.

Computers have to use binary as they're powered by electrical circuits that contain transistors.

These transistors can be switched on and off using electricity.

A transistor that is on represents a 1.

A transistor that is off represents a 0.

The more transistors there are, the more possible binary numbers can be represented.

Thank you so much for joining me for today's lesson and I hope to see you again very soon.

Bye.