edexcel gcse in computer science lesson activities for … · web viewyour teacher is going to read...

Lesson Activities Autumn Term year 11

GCSE (9-1) Computer SciencePearson Edexcel Level 1/Level 2 GCSE (9-1) in Computer Science (1CP1)

Lesson Activities for Autumn Term Year 11

LESSON ACTIVITIES FOR AUTUMN TERM YEAR 11The Lesson Activities in this document do not include preparatory work for the Non Examined Assessment (NEA), which can be found in the Autumn term Year 11 Scheme of Work (draft). In Lesson 2 of Weeks 2-12 students complete preparatory work for the NEA and in Lesson 2 of Weeks 13-15 they will start the NEA which continues in the Spring term.

Week 1Lesson activitiesThis week refreshes problem solving and programming, and introduces the Sample Assessment Material for the Non Examined Assessment (NEA).

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Week 2Lesson 1 activities

Activity 2.1.1The following cards should be printed and laminated if desired to make a simple card sort activity. One set is required per group of students in a class.

1 bit The smallest unit of storage

1 byte 8 bits

1 nibble 4 bits

1 kilobyte (KB)1 1024 bytes

1 megabyte (MB) 1 048 576 bytes (10242)

1 gigabyte (GB) 1 073 741 824 bytes (10243)

1 The Pearson Edexcel GCSE (9-1) Computer Science specification uses the binary definitions of kilobyte, megabyte and gigabyte for data storage. Full information can be found in the document ‘Definitions for file sizing and data transmission’.

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Activity 2.1.2

Fill in this table to help you see the difference compression makes to file size.

File A File B File CHow many characters does the file contain?

What type of content does the file contain?

What is its file size before compression?

What is its file size after compression?

What is its compression ratio (decompressed size/compressed file size)?

Which file compresses the most? Explain why.

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Activity 2.1.3Your teacher is going to read out or give you a series of binary numbers (see endnotei). The first pair of binary numbers represents a colour code as follows:00 = blue01 = white10 = yellow11 = greenThe second set of binary numbers represents the run length of the colour. So, for example 00, 1101 represents 13 blue pixels.

Assuming each of the squares in the grid below represents one pixel, listen to the series of binary numbers and shade the squares. The first line of pixels has been done for you.Line 1: 00 0001 01 0011 00 1100

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Activity 2.1.4 (Homework)

Use four different colours to ‘draw’ an image in the grid below.

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Now encode the above image using a 2-bit binary number to represent the colour depth and a 4-bit binary number to specify the run length of the pixels to be filled with that colour.

Line 1

Line 2

Line 3

Line 4

Line 5

Line 6

Line 7

Line 8

Line 9

Line 10

Line 11

Line 12

Line 13

Line 14

Line 15

Line 16

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Activity 3.1.1Use the image you encoded for your Activity 2.1.4 homework to complete these calculations.How many bytes are required to represent the uncompressed file?Remember: number of squares in grid x 2 / 8How many bytes are required to represent the RLE encoded file?Remember: number of codes x number of bits in each code / 8How much storage space have you saved?

ExtensionImagine that an image: contains 1,024 pixels (a grid of 32 pixels by 32 pixels) contains 255 different colours (represented by 8 bits)The image has been encoded using RLE, producing 116 binary codes comprising 8 bits (to represent the 255 colours) and 5 bits (to represent the colour run length).Using this information, calculate the following. How many bytes are required to represent the uncompressed file?

How many bytes are required to represent the RLE encoded file?

How much storage space have you saved?

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Activity 3.1.2Use the Run Length Encoding Calculator to encode these text strings. Your teacher will give you the URL to this.Text string AnswerAAAABBBBBBBBBCADDDDEEFFFFFFFF

ABCABCABCABCABCABCABCABCABCS

BBGGYYAACCFFEEBBGGYYAACCFFEE

Which one compresses the most?

Why is this?

Describe in English the process the RLE calculator follows to encode a piece of text.

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Activity 3.1.3An RLE compression algorithm works by removing repeated data and replacing it with a number representing the run length of that item.Fill in the gaps to complete this algorithm.

1. Start with the first character in the string.2. Write down the number 1.3. Compare the first character with the next character on the right.4. If they are the same, ___________________________________.5. If they are not the same, ________________________________.6. Move on to the next character on the right.7. Go back to step 2 and repeat until you reach the end of the string.8. _____________________________________________________.

Test out the algorithm using these data strings: o AAAABBBBBBBBBCADDDDEEFFFFFFFF

o ABCABCABCABCABCABCABCABCABCS

o BBGGYYAACCFFEEBBGGYYAACCFFEE

Activity 3.1.4 (homework)

Write a program in Python to implement the RLE compression algorithm you completed in Activity 2.1.3.

Activity 3.1.5 (extension)

Write a program in Python to decode a file compressed using RLE compression.

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Activity 4.1.1The wheels on the bus go round and round, round and round, round and round.The wheels on the bus go round and round all day long.

How many characters, including spaces and punctuation marks, are there in this song?Assuming one byte is used to represent each character, what is its file size?

Complete this table:Word Number of times used Number of bytes in wordThe 2 3wheels 2 6on 2 2the 2 3busgoroundandalldaylong

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Activity 4.1.2Complete this lookup table of all the words used more than once in the song.

Lookup table0. The1. wheels2. on3. the4.5.6.7.

Use the lookup table you have completed to encode the song, replacing repeated words with the number representing their position in the table.

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Activity 4.1.3A lookup table has been used to encode this text:Encoded text

0 1 2 3 generally more effective than 4 1 2 in reducing 5 size 6 7. However, whereas 4 2 allows 5 8 1 9 10 perfectly reconstructed from 5 compressed 1, 11 2 causes some 6 5 8 1 9 10 permanently lost. 0 1 2 3 most often 12 for media 7, i.e. music, pictures 13 videos.

This type 6 1 3 intended 9 10 12 14 humans whose brains are capable 6 ‘filling in 5 gaps’ created 14 11 2.MP3 uses 11 1 2 9 compress audio 7 for use on portable media players where space 3 limited. PNG 13 GIF use 4 1 2 9 reduce 5 size 6 image 7.

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0. Lossy1. data2. compression3. is4. lossless5. the6. of7. files8. original9. to10. be11. lossy12. used13. and14. by

Decode the text.

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Activity 4.1.4 (homework)Complete the Computer Science Unplugged worksheet ‘Extra for Real Experts’ (page 33 of http://csunplugged.org/wp-content/uploads/2015/03/CSUnplugged_OS_2015_v3.1.pdf). This worksheet will help you appreciate that storing patterns of letters in a lookup table can achieve big reductions in file size although picking out patterns of letters is just as easy for a computer as picking

out whole words, it’s much more difficult for human beings!

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http://csunplugged.org/wp-content/uploads/2015/03/CSUnplugged_OS_2015_v3.1.pdf

http://csunplugged.org/wp-content/uploads/2015/03/CSUnplugged_OS_2015_v3.1.pdf



Activity 5.1.1Use an image editor, such as pixlr’s photo editor online, to experiment with compression. Start with an uncompressed BMP file. Fill in this table.

Original BMP image JPEG with 100% quality[Insert image here] [Insert image here]

File size: File size:Image quality: Image quality:

JPEG with 50% quality JPEG with 25% quality[Insert image here] [Insert image here]

File size: File size:Image quality: Image quality:

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Activity 5.1.2Use a media player such as iTunes to experiment with music compression by encoding a music file using different bit rates.

Original uncompressed WAV file Higher quality MP3 (around 192kbps)

[Insert sound file here] [Insert sound file here]

Sound quality: Sound quality:Number of kbps: Number of kbps:File size: File size:

High quality MP3 (around 160kbps)

Good quality MP3 (around 128kbps)

[Insert sound file here]

Sound quality:

[Insert sound file here]

Sound quality:Number of kbps: Number of kbps:File size: File size:

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Activity 5.1.3 (homework)Lossless and lossy compression summary sheetExplain what is meant by lossless compression.

What type of data can be compressed using a lossless compression algorithm?

Describe how a lossless RLE algorithm works.

Some lossless compression algorithms use a lookup table. Explain what the lookup table is for.

Explain how lossy compression differs from lossless compression.

Explain why lossy compression is usually used for media files.

Outline the process of compressing an audio file using a lossy compression algorithm.

Outline the process of compressing a bitmap image using a lossy compression algorithm.

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Activity 6.1.1Check the system settings of your digital computers or search online for their technical specifications to find out the type of storage you are using.

Type of computer Type of storage device

Maximum storage capacity

Magnetic, optical or solid state?

Activity 6.1.2In preparation for the extended homework Activity 6.1.3 you will be asked in class to suggest and agree assessment criteria for the work. Note down this assessment criteria:

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Activity 6.1.3 (extended homework) Produce a presentation using an application of your choice (e.g. Powerpoint, Photostory, Prezi, Powtoon) explaining the three types of data storage (magnetic, optical and solid state).This homework will extend over three lessons.

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Activity 7.1.1Do the following:

Save a file onto the magnetic hard disk drive.Burn a file on to a CD or DVD.Save a file on to a solid state drive or a memory stick.

Now describe in your own words how the data in the file was stored on each of these types of storage.

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Magnetic storage, e.g. hard disk drive

‘The basic approach to magnetic data storage, however, is very similar for the different types of media. A read-write head moves very close to the magnetic surface - the distance is often no more than tens of nanometers. The head is able to detect and modify the magnetization of the material. The magnetic surface is divided into very small regions, each of which has a mostly uniform magnetization. As the head moves relative to the surface, the changes in magnetization from region to region are detected and recorded as zeros and ones. Different technologies vary in how the head moves relative to the surface of the media and how the regions on the media are organized, but the basic principle is the same.’(Source: http://study.com/academy/lesson/magnetic-storage-definition-devices-examples.html)

Optical storage, e.g. CD/DVD drive

Solid state storage, e.g. memory stick


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Activity 8.1.1The following cards should be printed and laminated if desired to make a simple card sort activity. One set is required per group of students in a class.Ask students to sort the cards into two piles: questions that have answers that are advantages for cloud storage and questions that have answers that are disadvantages for cloud storage.To increase challenge, ask students to rank each pile, by putting the ‘best’ advantage at the top and so on. Ask them what they mean by ‘best’. A further challenge could be added by asking students to consider the cons, in terms both of risk and impact (see solutions for example).

Where can I access my data from? Which computing devices can I use to access my data?

Is my data backed-up easily? Will my data stay private?

How much does it cost to start using? How easy is it to upgrade (increase capacity)?

What happens if a disk has a hardware fault? Can I change service provider easily?

What happens if the service provider goes bankrupt? What if my network is ‘down’?

What happens if the service provider servers go down? Will very large files cause problems?

What is the cost to upgrade (increase capacity)? Will I still ‘own’ my data?

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Activity 9.1.1 (Homework)Over the last three lessons you have been working on the same homework task. Your homework now is to evaluate how you met the success criteria for your homework.Return to the assessment criteria in Activity 6.1.2. Evaluate how successful you have been in meeting the criteria. Give reasons for this, and what would you do next time to improve your chances of meeting the criteria.

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Activity 10.1.1Research the following questions:IP addresses in the form 192.168.11.1 are called IP version 4 addresses. Each number is a single byte so the entire address is 4 bytes.

1. How many possible IP (version 4) addresses are there?

There are so many devices on the internet (about 10 billion) that we have run out of addresses.Recently IP version 6 has been introduced, which uses 16 bytes for each address.

2. How many possible IP (version 6) addresses are there?

3. Find out how many people there are on Earth.

4. Is that enough for each person on the planet to have their own IP address?

5. How do you think this will affect the number of IP addresses needed? Do you think IP version 6 will do?

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6. Find out what is meant by the ‘Internet of Things’.

Activity 10.1.2 (this may be set as extra homework if there are network restrictions)Every device has a unique hardware address called a MAC address (media access control).Look at your computer’s network configuration to find the MAC address of your computer.(If you are blocked from doing this, look at this image from a Windows PC instead: http://www.isaserver.org/img/upl/2004dh81115983842251.gif )

1. What is the physical (MAC) address of your device?

Use the lookup tool at http://www.coffer.com/mac_find/ to find the hardware company that provided this MAC address.

2. Does it match the company listed on your screen?

MAC addresses identify computers based on who manufactured their network card. It is more useful to identify computers based on which network they are connected to. In fact computers are grouped into sub-networks of usually only a few hundred devices, each with their own IP address.

3. What is the IP address of your device? (It should look something like this: 192.168.11.1 (four numbers separate by dots)).

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http://www.coffer.com/mac_find/


Each number is a single byte.4. What is the maximum value of 1 byte?

5. What is your IP address in hexadecimal?

Unlike a MAC address, an IP address is not pre-set. Some IP addresses are used only temporarily and when the computer is turned off, the address is given to someone else. When you use an IP address, the network learns what your MAC address is so that, if anyone wants to contact you, they can do so by using your IP address. If you know about mobile phones, the MAC address of a network connection is like the IMEI number of your mobile phone; the IP address is like your phone number. A person would not need to know your phone’s IMEI to call you; the phone network knows which phone number is which IMEI.

To view the MAC address of an Android device, choose Settings then About phone then hardware information

To view the MAC address of an Apple device, choose Settings then General then About (the MAC address is called the Wi-Fi Address)

Use the information on http://whatismyipaddress.com/mac-address to find out about:

6. Restricting access to Wifi networks by MAC address (you may have this policy in your school).

7. How the network learns which IP address is being used by which MAC address (ARP).

8. How DHCP controls access to IP addresses.

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http://whatismyipaddress.com/mac-address


Activity 10.1.3Split the class into two halves, one on each side of the room, with one student in the middle to act as the router.Give each student an IP address card while the router is told that one side has addresses starting 192.168 and the other side 10.10.Everyone writes a message to their friend starting with their own IP address (e.g. FROM: 192.168.11.3) and their friend’s IP address (e.g. TO: 10.10.10.5). Throw the messages into a pile on your own side only. Everyone looks for any messages addressed TO themselves and takes them out. The router picks up the remaining messages on each table and passes them across to the other side.To make the task more challenging, change the 10 addresses to be more complex numbers e.g. 192.168.12.Go further by having students choose any IP address they like and then contribute them to a routing table for the router before writing messages. (Point out the problem if students on either side choose sufficiently similar addresses.)

Possible simple IP address cards to cut out and use:

192.168.11.10 192.168.11.16 192.168.11.22 10.10.10.13 10.10.10.19

192.168.11.11 192.168.11.17 192.168.11.23 10.10.10.14 10.10.10.20

192.168.11.12 192.168.11.18 192.168.11.24 10.10.10.1510.10.10.21

192.168.11.13 192.168.11.19 10.10.10.10 10.10.10.16 10.10.10.22

192.168.11.14 192.168.11.2010.10.10.11

10.10.10.17 10.10.10.23

192.168.11.15 192.168.11.21 10.10.10.12 10.10.10.18 10.10.10.24

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Activity 10.1.4 (extension activity)A computer decides whether to send a packet directly to a recipient on the local network or to the router for forwarding to another network depending on the subnet mask.Each byte of the sender’s IP address and the recipient’s IP address is ANDed with the subnet mask. If the result is the same then they are both on the same network and can communicate directly. If not, they are on different networks and must communicate via the router.Review your notes from Section 2.5 last year (Boolean operations).For example, 12 AND 5 denary is 1100 AND 0101 in binary. 1100 AND 0101 = 0100 or 4 in denary so 12 AND 5 is 4.You can also use hexadecimal notation from Topic 3.Example1

Sender’s IP 192.168.11.1Recipient’s IP 192.168.12.5Subnet mask 255.255.0.0Sender’s subnet 192.168.11.1 AND 255.255.0.0 = 192.168.0.0Recipient’s subnet 192.168.12.5 AND 255.255.0.0 = 192.168.0.0Same network – do not use router

Example2Sender’s IP 192.168.11.1Recipient’s IP 192.168.12.5Subnet mask 255.255.255.0Sender’s subnet 192.168.11.1 AND 255.255.255.0 = 192.168.11.0Recipient’s subnet 192.168.12.5 AND 255.255.255.0 = 192.168.12.0Different network – send packets to router

Use the above information to write a program in a high-level language to determine whether two computers are on the same subnet.

Activity 10.1.5 (homework)Use a visual trace route tool to find out the ‘hops’ to your favourite websites and to take a screen shot of the most interesting or surprising route.

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Activity 11.1.1Answer these questions about the video:Question AnswerWhat chewed through Andrew’s internet?

What transmission medium is used for submarine cables to transfer bits under the oceans?

What does the router at 60 Hudson Street in New York do?

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Activity 11.1.2 (homework or practical activityComplete the table to include 10 domain names of your choice. Copy the domain name data below into a text file. Use http://ip-lookup.net/domain.php to find the IP address for each domain and create a CSV file. It should look something like this:

bbc.co.uk, 192.168.11.1

Write a program in a high-level language to search for the IP address of a given domain name in your CSV file.

Domain Name IP Address

bbc.co.uk

oxfam.org.uk

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http://ip-lookup.net/domain.php



Activity 12.1.1 Practical activity and homeworkCreate a simple web page using a text editor – this can be saved locally and opened using a web browser. Extend this activity by following the tutorial at http://www.w3schools.com/html/html_intro.asp until you have two or three linked pages.

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http://www.w3schools.com/html/html_intro.asp



Activity 14.1.1

Remember that computers take inputs, process those inputs and produce outputs.Choose three embedded computers you have discussed in class. For each one:

list the inputs and outputs describe the processing.

Choose one simple example, e.g. a room thermostat. Write an algorithm for the processing it needs to do, either as a flowchart or in pseudocode.

Acivity 14.1.2

Read the following and find other related articles. https://www.mepits.com/tutorial/299/Embedded-System/Embedded-Systems-in-Automobiles---A-Boon-to-Automobile-IndustryNow write about half an A4 page describing the benefits and disadvantages of embedded systems in cars.Include a bibliography of the web sites you have used.

Activity 14.1.3 (homework)Think about the objects around you. Justify redeveloping an object to include an embedded system which can link to the Internet of Things.You should cover:

The benefits to yourself of this object The benefits to society Legal implications Ethical and moral implications Environmental implications

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https://www.mepits.com/tutorial/299/Embedded-System/Embedded-Systems-in-Automobiles---A-Boon-to-Automobile-Industry

https://www.mepits.com/tutorial/299/Embedded-System/Embedded-Systems-in-Automobiles---A-Boon-to-Automobile-Industry



Activity 15.1.1Research the following internet-enabled devices. What are the pros and cons of these technologies?

Hello Barbie http://www.thestar.com.my/tech/tech-news/2015/12/02/high-tech-barbie-stokes-privacy-fears/

Self-driving cars http://www.bloomberg.com/news/articles/2015-12-18/humans-are-slamming-into-driverless-cars-and-exposing-a-key-flaw

Smart meters http://www.which.co.uk/consumer-rights/problem/do-i-have-to-accept-a-smart-meter

Drones http://techcrunch.com/2015/10/20/parrot-enables-autonomous-flight-for-the-bebop-drone/

Fitbit http://www.nbcnews.com/tech/security/fitbit-owners-not-risk-malware-company-says-n449176

Google glass https://en.wikipedia.org/wiki/Google_Glass

Telematics http://www.telegraph.co.uk/motoring/news/10110097/Smartphone-apps-that-monitor-how-you-drive.html

Activity 15.1.2Create a quiz about embedded systems. This can be a multiple choice, or fill in the blanks format. You should include answers to the questions.

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i List of binary numbers for Activity 2.1.3:

Line 1 00 0001 01 0011 00 1100Line 2 00 0001 01 0011 00 1100Line 3 00 0001 01 0011 00 0100 10 0010 00 0100 10 0001 00 0001Line 4 00 0111 10 0010 00 0100 10 0010 00 0001Line 5 01 0010 00 0101 11 0011 00 0011 10 0010 00 0001Line 6 01 0010 00 0011 11 0110 00 0001 10 0011 00 0001Line 7 00 0100 11 0010 01 0001 11 0101 10 0011 00 0001Line 8 00 0001 01 0001 00 0001 11 1001 10 0011 00 0001Line 9 00 0011 11 1001 10 0011 00 0001Line 10 00 0001 01 0001 00 0010 11 1000 10 0011 00 0001Line 11 00 0101 11 0110 00 0001 10 0011 00 0001Line 12 00 0111 11 0011 00 0011 10 0010 00 0001Line 13 00 0001 11 0001 00 0010 11 0001 00 0010 10 0010 00 0100 10 0010 00 0001Line 14 00 0001 11 0001 00 0001 11 0001 00 0100 10 0010 00 0100 10 0001 00 0001Line 15 00 0010 11 0001 00 1101Line 16 10 10000

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