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GRADE 8
THINKING LIKE A COMPUTER
Tim Bell stands in front of a crowd of squirming elementary students. He sticks five candles into a cake, lights three and declares it fit for a 21st birthday. Even an audience that can barely spell the word "computer" knows that 21 candles belong on the cake.
But Bell, an associate professor of computer science and software engineering at the University of Canterbury in New Zealand, is not talking about simple arithmetic. On this particular Saturday morning, he is at Butler University to explain binary code and other scientific computer concepts to kids during a one-hour presentation.
Bell is on a mission to explain to teachers and students the technology that lurks behind a computer screen by using games and props, but no computer.
Why no computer? PCs aren't flashy or exciting, particularly to kids raised on Nintendo, Bell says. Besides, computer science needs to get creative to compete with imaginative science demonstrations, such as Mad Science camps, which feature rocket making, exploding model volcanoes or nails being hammered with frozen bananas. Odd props work better
"Using the Internet or a CD-ROM is hardly computer science," says Bell. "Computer science is a subject full of elegant data structures and apparently intractable problems."
To capture kids' attention and intellect, Bell uses cheap props like a felt-board magic trick to show how to detect computer errors and Twister-like mats to demonstrate computer sorting networks. He certainly catches the attention of Brianna Sorenson, 7, a volunteer for several stunts."My favorite part is pretty much everything," she says, as she skips around the room.
Bell is traveling worldwide in 2006. He's been in Sweden, China and all over North America, from Portland, Ore., to Portland, Maine. His show, financed by Google and his university, is called "Computer Science Unplugged," and can be performed in a variety of settings, such as science museums, schools or even around a kitchen table. His presentations are free, and Bell hopes that teachers and students will want to learn more about the science behind computers after attending them.Explaining a bit
But back to Bell and binary:Computers don't use the numerals 0-9, or letters of the alphabet. They use binary code, which uses only 0 and 1, known as "bits." The order of the 0s and 1s determines the number.
In one demonstration, Bell places five volunteers in a row -- each with an oversized flashcard that represents a bit. The card at the far right has just one dot on it. Each subsequent card has double the number of dots. The cards are flipped -- either face up, which always represents the numeral "1;" or face down, representing the numeral "0."To figure out the Arabic numeral, the audience adds up the dots that are face up.
For example, using five cards, the number "8" would be: 01000 in binary code; the number "17" would be: 10001.The kids (and even some adults in the crowd) get that "Gee-whiz-I-get-it" look on their faces after this binary brainstorm session.
The friendly professor further explains binary with the birthday cake. Bell asks if anyone in the audience is celebrating a birthday in the next week, and a middle-aged Butler computer scientist timidly lifts his hand.Bell jokingly concludes that the birthday boy is likely 21 -- or so -- and makes 21 in binary code with the five candles:
The first candle (representing 16) is lit.The second (representing 8) is not.
The third (representing 4) is lit.The fourth (representing 2) is not.
The fifth (representing 1) is lit.The binary number is 10101.
"Participatory activities are more likely to appeal to the audience's curiosity, and interest can be increased by making an activity competitive or, even better, cooperative problem solving," says Bell.Bell's presentations depend on audience participation. Courtney Petrie, 10, a fifth grader at Forest Glen Elementary School in Lawrence Township, waves her hand wildly to volunteer for another "trick."
Evening his odds
Courtney approaches a large piece of red felt hanging from the wall. Bell hands her a stack of 36 black and white squares to stick onto the felt. Bell watches Petrie place most of the squares in random order, then adds a row and turns his back, inviting Petrie to flip any square from white to black. After she does so, Bell turns around and knows with one glance which of the squares has changed color.
Bell relies on "a parity check," not his memory, for this activity. After Petrie places most of the black and white "bits" on the felt, Bell adds an extra set, giving all columns and rows an even number of white squares. He is able to instantly spot the changed "bit" by noting the row with an odd number of white squares. This trick shows how to detect corrupted computer data and fix it. Another topic is the illogical side of computers. Computers frustrate people instead of help them because of the way they give directions. For example, a PC gives only the option of clicking 'OK' when it brings a problem to the user's attention.Something else that Bell finds idiotic is that you must push the start button to stop many computers. Bell says that society needs more computer designers who know how normal people react to technology.
Bell says he's motivated to excite children about computers and how they work so future generations will continue to advance the technology."Almost everyone uses computers," he says. "They use the Internet, they search on Google, they have cell phones -- which are also computers -- or they might have an MP3 player.
"But what I worry about most is that we don't have any children or university students that are going to be able to make computers in the future. They know how to use them, but not how to design them."Unplugged help
"Computer Science Unplugged," a book that Bell co-authored with Ian H. Witten and Mike Fellows, provides teachers with activities that explore ideas in computer science without using a computer. The book also is a good introduction to how computers work.The book may be ordered from lulu.com, a print-on-demand book service. The download of the book costs $18.25; a printed version is $25.
To learn more about "Computer Science Unplugged," go to the project Web site: http://www.unplugged .canterbury.ac.nz/.
Copyright 2006 Y-Press