Lesson video

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

In this lesson, we will look at different coding schemes and look at how messages can be encoded and decoding by looking at a few different examples of coding schemes.

So let's get started.

Welcome to today's lesson.

Today's lesson is called "Representing Characters" from the Unit, Data representation: text and numbers.

And by the end of this lesson, you'll be able to encode, transmit, and decode short messages using different coding schemes.

There are four keywords to today's lesson.

Coding scheme.

Coding scheme is a system where a code is used to represent something.

ASCII.

ASCII is a character set that represents each character with a unique numerical value.

Encode.

Encode is converting information from one form into another.

Decode.

Decode is converting encoding data back to its original form.

There are three sections to today's lesson.

The first is recognised different coding schemes.

The second is encode and decode a message.

And the third, measure the length of a representation.

So let's start with recognise different coding schemes.

Two friends live in huts on opposite sides of a great lake.

How can they exchange messages from a distance? And note that they do not have access to mobile phones or computing devices.

Lucas says, "The two friends could use flag semaphores." Aisha says, "They could use light signals using a torch, this would work best in the dark." Izzy says, "They could use Morse code if they have the correct equipment." All really good examples of how we could communicate over a distance.

All of these methods are examples of coding schemes.

A coding scheme is simply a set of rules that defines how symbols mapped to another form.

For example, in Morse code, the following sequence is used to represent the character "a".

And it's you say it as a dot and a dash.

So dot, dash equals A.

Everyone using Morse code uses this sequence for the character "a" to allow communication to happen.

The Morse code representation for the characters A to Z.

Each character is represented by a combination of dots and dashes, and you can see there the letters A to Z and each one that's represented with either a dot, a dash, or a combination of both.

Let's have a quick check.

Fill in the gaps to complete the sentence.

A blank is simply a set of blank that defines how blank map to another.

And you have the words rules, coding scheme, and symbols.

Pause the video to consider your answer, and then we'll check it.

Let's check your answer.

A coding scheme is simply a set of rules that defines how symbols map to another form.

Well done if you've got that correct, ASCII is a coding scheme that represents characters, letters, numbers, and symbols as numbers.

You can find the codes by looking at an ASCII table.

This part of the table shows the values for the lowercase characters, a to z.

You can see the first column has characters in, a to z.

The next has the ASCII code, and then we also have the binary code.

Braille is a system of raised dots that can be read with the fingers.

It's used by blind people and people with low vision.

In braille, letters and numbers are made of a rectangle with six dots in two columns.

Each letter and number uses a different pattern of raised dots.

You can see the here, for instance, on letter A, you have one raised dots and the others are not raised.

Let's have a quick check.

Which coding scheme uses a series of dots and dashes to represent each character? A, braille.

B, ASCII.

C, Morse code.

Pause the video to consider your answer, and then we'll check it.

Let's check your answer.

The answer was C, Morse code.

Well done if you've got that correct.

Let's do an activity.

Explain what is meant by a coding scheme.

Identify the following coding schemes.

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

Let's check your answers.

The first question was explain what is meant by a coding scheme.

A coding scheme is a set of rules that assign symbols, usually numbers or letters to represent information.

The second part was identify the following coding schemes.

A was Morse code, B was ASCII, and C was braille.

Well done if you got those correct.

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

Encode and decode a message.

You have seen some examples of coding schemes.

There are two important steps when using a coding scheme.

Encoding, converting information from one form into another, typically to make it easier to store, transmit, or process.

Decoding, reversing the process, converting encoded data back into its original form, making it understandable or usable.

Let's take the example of sending the word "cat" using Morse code.

You can see on the left, we have the original message "cat".

It goes through the encoding and it comes out as dash dot dash dot, dot dash, dash.

And each sequence of dots and dashes there is representing a individual letter.

And if we look at that the other way, we now have the encoded message of dash dot dash dot, dot dash, dash.

And to decode it, we now look at each one of those sequences of dots and dashes and reverse the process to decode it back to cat.

Let's have a quick check.

What is the encoded version of the word "dog" in Morse code? A, dash dot, dash dash dash, dash dash dot.

B, dash dot dot, dot dash, dash dot dot.

Or C, dash dot dot, dash dash dash, dash dash dot.

Pause the video to consider your answer, and then we'll check it.

Let's check your answer.

The answer was C, dash dot dot, dash dash dash, dash dash dot.

Well done if you got that correct.

In computing, encoding means converting text, images, videos, and other data formats into binary digits.

See in this image here, A equals 65, we have the binary number there in the encoding stage into the computer.

After processing and transmission, the binary digits are converted back into human readable text or formats.

Let's have a quick check.

Decoding is best described as.

A, converting A message into signals or symbols for transmission.

B, reducing file size through compression.

C, reconstructing original information from received symbols.

Or D, encrypting data for privacy.

Pause the video to consider your answer, and then we'll check it.

Let's check your answer.

The answer was C, reconstructing original information from received symbols.

Well done if you got that correct.

Let's do an activity.

Use the following coding schemes to encode these messages.

A, using Morse code, encode "babbage".

Using ASCII, encode "hopper".

And using braille, encode "vaughan".

Note that coding schemes can be found in additional material for this lesson.

The second part of this activity is to use the following coding schemes to decode these messages.

And you have an ASCII sequence there and also a Morse code.

So using the additional material, again, decode these messages.

Pause the video, go back through the slides, use the additional material, and complete activities one and two, and then we'll go through the answers.

Let's check your answers.

For the first part, Morse code using that coding scheme to encode babbage would've been dash dot dot dot, dot dash, dash dot dot dot, dash dot dot dot, dot dash, dash dash dot, dot.

Using ASCII to encode the word "hopper" would be 1101000, 1101110, 1110000, 1110000, 1100101, 1110010.

And using braille to encode vaughan, you can see how that would look there with the dots, the raised dots in the rectangle shape.

For the second part of the lesson was using the given ASCII and Morse code to decode those messages.

So the first one decoded was berners-lee, and the second one decoded was Shannon.

Well done if you got those correct.

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

Measure the length of a representation.

The coding schemes that you use to associate each letter with a sequence of symbols.

The total number of symbols in the sequence is known as the representation length.

Look at this example of a Morse code message.

The original message "babbage", the coded message you can see here is the dots and the dashes.

There are seven symbols, seven letters.

There are 20 symbols with 6 spaces.

If we encoded the same original message using ASCII, the original message, again, being babbage and the coded message you can see there in the binary format.

There are seven symbols still for the letters.

There are 49 symbols and 6 spaces now with this one.

Let's have a quick check.

True or false.

The representation length does not include any spaces.

Pause the video to consider if that is true or false, and then we'll go through the answer.

Let's check your answer.

The answer is false.

The representation length is the total number of symbols in the sequence, including spaces.

Well done if you got that correct.

In computing, the symbols used are 0 and 1.

Every piece of information is represented as sequences of 0s and 1s.

How could the symbols 0 and 1 be represented in the real world? Aisha says, "We could use a torch.

If the torch is on, it represents a 1.

If it is off, then it represents a 0." Izzy says, "We could use holes punched out of paper.

A hole could represent a 1." Let's have a quick check.

Why have people invented so many different coding schemes? Pause the video to consider your answer, and then we'll check it.

Let's check your answer.

Izzy says, "Because there are so many different ways to communicate." Aisha said, "Different schemes work for different situations." Lucas has said, "For when oral communication isn't enough.

For example, when things need to be written down." Well done if you've got any of those.

Let's do an activity.

What are the lengths of the following representations? We have the original message "computing" and the coded message there using the dots and the dashes for Morse code.

The second part, we have the original message "computing", and we have the coded message there with binary.

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

Let's check your answers.

So the first one was the original message "computing" and using the Morse code.

There are nine symbols, letters, in the word "computing".

Using Morse code, there are 24 symbols with 8 spaces.

The second part, again, we've got computing.

So it's nine symbols, nine letters.

And at the coded message this time, we have 63 symbols and 8 spaces.

Well done if you've got those correct.

In summary, character coding schemes like ASCII, are used to represent letters, numbers, and symbols.

In computing, every piece of information is represented as sequences of 0s and 1s.

The length of a representation is the number of symbols, including spaces it contains.

Well done for completing this lesson, "Representing Characters".