Hints for presentation

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Center for Embedded Networked Sensing University
of California, Los Angeles CS4HS Workshop July
23, 2009
And kinesthetic computer science activities
Lynn Lambert Christopher Newport
University Newport News, Virginia
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Author Tim Bell (not pictured Ian Witten and
Mike Fellows)
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Global project
New Zealand Sweden United Kingdom Korea Japan Chin
a Haiti Even USA (CSTA, Peter Denning,
Carnegie-Mellon, SIGCSE, AP Reading, NECC)
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What is Unplugged

• How to teach important computer topics without
  using computers at all!
• Have Fun!
• www.csunplugged.org

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Like?

• Binary Numbers
• Image Representation
• Text Compression
• Error Detection and Correction
• Searching Algorithms
• Sorting Algorithms

• Sorting Networks
• Minimal Spanning Trees
• Routing and Deadlock
• Finite-state Automata
• Programming Languages
• Information Theory

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Magic Trick
Magic
Make a 5x5 grid with colored squares, some with
one color, some the other.
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Parity Checking

• Even parity
• Can detect a bit that was corrupt
• ISBN detects adjacent swapped digits or a single
  incorrect digit
• X10 (1x1 2x2 3x3 4x4 5x5 6x6 7x7
  8x8 9x9) mod 11
• Harry Potter and The Deathly Hallows
  0-545-01022-5
• (01 52 43 54 05 16 07 28
  29 )
• (0 10 12 20 0 6 0 16 18) 82
• 82 mod 11 5

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Binary Digits
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BINARY NUMBERS

• HAPPY BIRTHDAY, Daniel Radcliffe !

Daniel Radcliffe turns 20
0 0 1 0 1 0 0
Born July 23, 1989
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Characters in Binary
1
2
3
4
5
E
A
B
C
D
E
01000
H
6
7
8
9
10
00101
E
E
F
G
H
I
J
01100
L
15
11
12
13
14
01100
L
E
L
M
O
N
K
01111
O
16
17
18
19
20
Q
E
P
R
S
T
22
23
24
25
26
21
E
E
U
V
W
X
Y
Z
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Characters and Sound Represented in Binary

• ASCII
• Modem

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Image Representation(black and white)

• Each pixel is a bit

1440 900 1,296,000 pixels/bits
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Image Representation(black and white)

• Each pixel is a bit
• 00001111111111100 for first row
• etc.

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Image CompressionRun Length Encoding
4, 11, 2 4, 9, 2, 1, 1 4, 9, 2, 1, 1 4, 11, 2 4,
9, 4 4, 9, 4 5, 7, 5 0, 17 1, 15, 1
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Image Representation(Color)

• Each pixel is a bit
• Still 1,296,000 pixels
• Now, each pixel is

32 bits
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Color Images

• RGB color
• 0 0 255 for blue
• 00000000
• 00000000
• 11111111

Microsoft Office Color
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204/102/0
226/113/0
226/113/0
196/198/0
204/102/0
226/113/0
180/90/0
141/105/101
204/102/0
240/240/255
230/206/158
179/102/38
141/105/101
232/238/228
218/218/200
217/187/63
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Routing and Deadlock

• Orange Game

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TREASURE HUNT Finite State Automata (FSA)

• FSA are theoretical state models
• Unplugged uses a treasure hunt.
• Others
• letters to accept particular words
• a metro map for getting to a particular location

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TREASURE HUNT
What is the quickest route?
Finite State Automata
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Yesterday by The BeatlesL-Z Compression

• Yesterday love was such an easy game to play
• Now I need a place to hide away
• Oh, I believe in yesterday.
• Why she had to go
• I dont know, she wouldnt say.
• I said something wrong
• Now I long for yesterday.

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MARCHING ORDERSProgramming Languages

• One of the most frustrating things about
  programming is that computers always obey the
  instructions to the letter, even if they produce
  a crazy result.

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CS Unplugged in High School (by Scott Fletcher)

• Perfect Binary Numbers, Programming Languages
  ("first day exercise). 
• Image Representation to introduce computer
  graphics to the students. 
• Text Compression (used a popular song that the
  kids would recognize)
• Used briefly to introduce a topic Twenty Guesses
  or the Card Flip Trick
• Sorting Networks Algorithm, Minimal Spanning
  Trees, Treasure Hunt could have been more
  challenging
• Did not use
• Battleships (pretty involved)
• Lightest and Heaviest (too much equipment)
• Orange Game (but should have)

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Have you used Unplugged? How?
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Sorting and Searching

• In the book
• Battleship (Searching)
• Lightest and Heaviest (Sorting)
• Sorting Network
• Your ideas

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BATTLESHIPS Search Method 1
GAME 1 Ships are in random order.
FIND SHIP 9264
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BATTLESHIPS
GAME 2 Ships are in increasing order.
33 183 730 911
1927 1943 2200 2215 3451
3519 4055 5548 5655
5785 5897 5905 6118 6296
6625 6771 6831 7151 7806
8077 9024 9328
FIND SHIP 5905
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BATTLESHIPS
GAME 3 Ships are ordered into 10 groups based
onthe sum of the digits of the ship modulo 10.
9308 1478 8417 9434
3121 9503 1114 7019
6519 2469 5105
1524 8112 2000
9050 1265 5711
4200 7153 6028
2385 5832 1917
1990 2502
4135
FIND SHIP 9503
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BATTLESHIPS

• These three games illustrate
• linear search
• binary search
• hashing
• What is the maximum number of guesses required
  for each of these search techniques for n
  battleships?

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LIGHTEST HEAVIEST

• Start with a few (6 or 8) containers with
  different amounts of sand or water inside. Seal
  tightly.
• Children are only allowed to use the scales to
  compare the relative weights of two containers.
• Only two containers can be compared at a time.

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LIGHTEST HEAVIESTMethod 1 Selection Sort

• Find the lightest of the containers using the
  weights they have been given, using only the
  balance scales.
• Now compare that with another, keeping the
  lighter from the comparison. Repeat until all the
  objects have been used.

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LIGHTEST HEAVIESTMETHOD 2 Quick Sort

• Choose one of the objects at random.
• Compare each of the remaining objects with it,
  and put them in one of two groups. Put those that
  are lighter on the left of the object in the
  middle, and those that are heavier on the right
  (there may be no objects in one of the groups).
• Repeat this procedure on each of the groupsthat
  is, use the balance to divide the groups into
  subgroups. Keep repeating on the remaining groups
  until no group has more than one object in it.
  The objects will be in ascending order.

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Sorting network
lt
Left
gt
Right
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Sorting and Searching

• In the book
• Battleship (Searching)
• Lightest and Heaviest (Sorting)
• Sorting Network
• Your ideas

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Non CSUnplugged Activities

• Andy Begel, Steve Wolfman, Dan Garcia KLA
  (Kinesthetic Learning Activities),
  http//ws.cs.ubc.ca/kla/,
• Binary Tree
• Recursion
• cons, car, cdr
• AP Reading Toy Night with Robert Duvall
• Internet, Sorting, Searching
• AP list, CSTA

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THE MUDDY CITY

• Our society is linked by many networks
  telephone, utilities, roads
• For a particular network, there is usually some
  choice about where the links can be placed.
• This exercise examines a complete network to
  determine the links necessary to connect all the
  components of the network at minimal cost.

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THE MUDDY CITY
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THE MUDDY CITY
a graph
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THE MUDDY CITY
a graph
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THE MUDDY CITY

• This exercise illustrates how to build what we
  call the minimal spanning tree.
• A tree does not have any cycles where you can get
  back to where you were before.
• This exercise does not give us the shortest path
  from one location to another.
• But there is another algorithm for that!

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Peruvian coin toss

• Try for a fair coin toss over the phone

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Information Theory

• Can you read the following sentence?
• Ths sntnce hs th vwls mssng.
• You probably can, because there is not much
  "information" in the vowels.
• This activity introduces a way of measuring
  information content.

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Shannon theory

• Twenty questions
• Guess a number

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Shannon theory

• Guess a letter
• Guess a sentence
• Probability and information

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Your Turn

• Break up into groups, and answer at least one of
  the following
• What unplugged or unplugged-like activities have
  you done in your classroom? What worked/didnt
  work?
• Create an activity that you and others can use in
  a classroom.

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Example mappings

• What unplugged or unplugged-like activities have
  you done in your classroom? What worked/didnt
  work?
• Create an activity that you and others can use in
  a classroom.
• Props you can use
• Cards
• two sides, choice, combinations, permutations
• Cups, containers, buckets
• hidden information, two states, variable, limited
  contents
• Stickers, marker pen
• commit, label, colour, user input
• Chalk on pavement/ tape on floor
• transitions, paths, target
• Board game
• paths, chance, rules
• Food
• competition, humour, colour, sharing, size
• String
• Connection, communication, length, network

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Your Turn Reporting
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Cryptography

• Public/Private Key
• One Way Functions
• Send Information

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One way function

• Both have the same telephone book
• Pick a function
• Odd/even length of name
• Name begins with H/T

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Select name
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Record phone number

• 332-6308

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Presenter guesses H or T?

• 332-6308

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Presenter tries to find name
332-6308
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Human-Computer Interaction
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Stop the computer...
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Stop the computer...
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HCI

• Works sheets
• Affordances for doors
• Layout of ovens
• Dumb interfaces
• System is machine plus user

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CS Unplugged wants your ideasDesigning an
activity

• What are the key elements?
• e.g. bits, states, compare, relationships
• What games/puzzles/toys use similar elements?
• Turn it into a challenge
• To find (best) solution
• Compare speed (of groups or methods)
• Team?
• Impediments?
• Evaluate
• Simplicity, engagement, cost, novelty
• Refine
• Show to lots of kids/teachers/profs
• Publish

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Questions?