Yr8_HT4_L4 Characters in Binary

Open Ended

Imagine you have a word document open...What do you think happens when you press the 'A' key on your keyboard?

Use these words: (input, keyboard, CPU, output, monitor, binary):

[3 mins]

Characters in Binary

KS3

Understanding binary

​CPUs in computers can only process binary.

In our daily lives, we use the English alphabet and regular numbers.

So we need a way to store these English letters and numbers in binary.

The need for character sets

So, computer scientists have designed character sets -> the possible characters that can be represented by a number system.

There are three in use...Today you will learn about ASCII

Multiple Choice

What is a character set?

[20 sec]

• What language can be used in a computer system

• The possible characters that can be represented by a number system

• The characters that make up a movie scene.

Introduction to ASCII

In ASCII (American Standard Code for Information Interchange):
- each letter and number is given an ASCII code
- this can then be translated into binary.

Multiple Choice

What does ASCII stand for?

[20 sec]

• Australian Standard Code for Information Interchange

• Any Set of Characters In the Internet

• All Set Characters In Information

• American Standard Code for Information Interchange

ASCII table

Originally, ASCII used 7 bits, giving us a maximum of 128 possible characters that can be represented

For example, in the right, you can see that the 'space' key is represented by ASCII code 32.

Extended ASCII

Because we need more characters to represent, we can use Extended ASCII using 8 bits, which has 256 possibilities.

For example, the Spanish accented a is represented by ASCII code 225.

An example of ASCII

Here, we can see that A is stored as an 8-bit binary number.

A = 0100 0001

Fill in the Blanks

ASCII codes

The ASCII Code for A is 65.

The ASCII code for B is 66

The ASCII code for C is 67

What do you think the ASCII code is for...

- D?

- F?

Multiple Choice

What is the ASCII code for A?

• 65

• 66

• 67

• 68

Multiple Choice

What is the ASCII code for B?

• 65

• 66

• 67

• 68

Multiple Choice

What is the ASCII code for C?

• 65

• 66

• 67

• 68

Multiple Choice

What is the ASCII code for D?

• 65

• 66

• 67

• 68

The ASCII Table

Here is the ASCII table.

It goes from 0 -> 127 (128 possibilities)

Note:
0-31 have been hidden as they are non-printable characters.

Match

Click on the ASCII table in the picture to match the following:

• 32

• 65

• 97

• 64

• 127

the space key

A

a

the @ symbol

the DEL key

• the space key

• A

• a

• the @ symbol

• the DEL key

Converting between ASCII codes and English

KS3

The ASCII Table

Here is the ASCII table.

Let's find out what this says:

0100 1000 => H
0110 1001 => i
0010 0001 = !

This binary number says Hi!

The ASCII Table

This time, let's use the ASCII codes...

What does this say?

ASCII code: 65, 83, 67, 73, 73

Work it out!

Fill in the Blanks

The ASCII Table: Harder

In real-life, ASCII will be stored like this...
Can you find out what this says using 8-bit ASCII:

01010000011010000110010101110111

Hint: Try splitting the binary number into bytes (8-bits)

See the next slide for the answer!

The ASCII Table: Harder

It is actually four bytes that represent four characters!

01010000/01101000/01100101/01110111

Phew

Independent Tasks

KS3

Your tasks

In PowerPoint, can you:
1. write your name in ASCII using the binary code?

2. write the binary for CoMpUtInG

3. convert binary to text

4. convert more binary to text

5. convert lines of binary to text