Background and Introduction

One of the first calculating tools, the abacus, was developed thousands of years ago. Computers use the same principles as the abacus to perform arithmetic, except instead of pushing beads along dowels, computers use electrical signals. This code of electrical signals is based on the idea that information can be represented with only two digits, 1(on) and 0 (off). This is called binary code. The first system of binary numbers was introduced in the 1600s. Like many scientific discoveries, binary numbers were first proposed to solve theoretical problems. Practical applications came later.

In the 1830s Charles Babbage, a British inventor, conceived of a machine that could be given instructions to perform different tasks and store results, which he called the Analytical Engine. Ada Byron, also known as Lady Lovelace, learned about Babbage's work, corresponded with him, and added her own ideas. In 1843 she published an article predicting that such a machine might be used to compose music, produce graphics, and do scientific work. Ada suggested a plan for how the engine might calculate Bernoulli numbers. This plan is now regarded as the first "computer program."

The first electronic computer was built in the twentieth century. During World War II, the US government needed to solve large complex problems. In the early 1940s, computers used electromechanical relay switches. Instructions were translated into binary code, and transmitted as punched holes in reels of paper. Punched holes were 1s and were read as ON, allowing current to flow through the paper. Zeroes were covered and read as OFF, and the current would not flow through the paper. Although this was laborious work, once the computer was programmed, repeated computations could be performed quickly.

In 1945, at the Moore School of Engineering at the University of Pennsylvania, the Electronic Numeric Integrator and Computer (ENIAC) was developed. Its assignment was to calculate rapidly the complicated ballistic tables used to aim weapons accurately. By converting numbers into digital code which could be easily manipulated, ENIAC operated 10,000 times faster than mechanical devices. However, the ENIAC used thousands of vacuum tubes and was so huge that it filled a building the size of a gymnasium.

Until the mid 1950s all electronic devices used vacuum tubes. Failures were frequent because of the limited lifetime of the heating filaments and massive power requirements of the tubes. The invention of the transistor in 1947 by John Bardeen, Walter Brattain, and William Shockley revolutionized electronics. The transistor became an ideal substitute for the vacuum tube for most purposes, because it was more reliable, required much less power, and produced little heat. Transistors enabled computers to become smaller and more efficient, yet with greater complexity of design. By 1959 practically all computer manufacturers used transistors. During the 1960s transistors displaced vacuum tubes in television sets and radios.

The next important step in computer history was the integrated circuit, developed independently by Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor. Electronic elements and connections are embedded on a small wafer of silicon. Several transistors can be placed on one chip, increasing miniaturization and reliability by decreasing the number of components to be placed on a printed circuit board. The greatest breakthrough in chip technology came during the early 1970s with the introduction of the first computer memory chips and microprocessor chips, heralding the development of the microcomputer a few years later.

The development of computers and digital electronics can be termed a technical revolution. Computers progressed from cumbersome electronic renderings of electromechanical machines to highly flexible and user-friendly machines. Their application spread from "number crunching" into all areas of human activity. Software -- nonexistent when the first computers were built -- developed quickly. Today we use computers to organize words, numbers, and pictures in our homes, schools, offices, stores, theaters, baseball parks, and cars.

The parts of a computer
All computers work by taking input, processing or storing that input, and returning output. People instruct the computers what to do.

To perform a task, a computer first needs input. The keyboard is the most common input device. A scanner or video camera can deliver information and images to a computer. The computer then interprets and carries out instructions, receives, sends, and stores information using circuit boards. Computers store the programs and files in their memory. Disks store information in magnetic patterns which can be used to manipulate electric current.

Output is the text, picture, graph or sound that is returned after it is processed. The visual monitor is the most common output device. A printer puts information onto paper.

Finally, computers need software. Software or computer programs are lists of instructions written by a person that tell a computer what to do. Software is stored as a set of electromagnetic code signals in the computer's memory, on a disk or microchip.

Software and hardware designed to send and receive data allow computers to share information with other computers and people around the world. Modems translate computerized data into signals that travel through phone lines.[1]

Benchmarks for Science Literacy [2]

grades 3-5	Computers are controlled partly by how they are wired and partly by special instructions called programs that are entered into a computer's memory.
grades 6-8	Computers have become invaluable in science because they speed up and extend people's ability to collect, store, compile and analyze data, prepare research reports, and share data and ideas with investigators all over the world. Most computers use digital codes containing only two symbols, 0 and 1, to perform all operations. Continuous signals (analog) must be transformed into digital codes before they can be processed by a computer.
grades 9-12:	Computer modeling explores the logical consequences of a set of instructions and a set of data. The instructions and data input of a computer model try to represent the real world.

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Activity: It's as Easy as 1, 2, 3

Materials
large jacket or shirt

Background for Instructors
Computers are only as good as the instructions they receive from people. Human computer programmers strive to translate human language into a code that a machine can recognize and understand. Successful programming requires that a task be broken down into steps that can be understood not only by the computer, but also by other programmers. This set of steps is called an algorithm. An algorithm is a procedure for accomplishing a task by carrying out a precisely determined sequence of simple, unambiguous steps.

In this activity, participants will try to break down the everyday task of putting on a jacket into simple step-by-step instructions that a computer robot could understand. It's not as easy as it seems!

This activity demonstrates a similarity between computer mechanics and biology. Specificity and accuracy of information is important in genetics as well as in computers. DNA transmits complicated yet precise instructions to make new cells. In cells, just as in computers, confusion or mutation results when instructions are rearranged or deleted.

Objectives

• break down a common, yet complex task into step-by-step instructions
• model a computer program

Procedure

• Ask for one volunteer who will be a computer robot (consider asking an adult to volunteer). The robot can only do exactly as it is instructed. Ask the robot to temporarily leave the room so she does not hear you explain the task to the other campers. (This way the robot cannot unconsciously help with the instructions).
• Explain to the group that you want the robot to do a very simple task: successfully put on a jacket. Place the jacket on the floor and invite the robot back in.
• Ask one volunteer to suggest the first step. For example a camper says, "Put your arm in." The robot should do exactly this: place her arm out in the air.
• Ask a second person for another suggestion. For example the next camper says, "Pick up the jacket." The robot should pick up the jacket regardless of orientation.
• Continue asking for suggestions. Each time, the robot should do exactly as she is instructed. If an instruction is too vague, such as "Put the jacket on," the robot can ask for another, more specific instruction (or hold up an error message). Remind campers to speak one at a time, and encourage lots of people to participate.
• Eventually, with lots of trial and error (and giggles), the robot should end up successfully jacketed.
• Try again with a different robot and a different task, such as putting the jacket on inside out.
• Discuss how this relates to writing instructions for a computer.

Materials
Index cards or slips of paper with large numbers written on them
pencils

Background for Instructors
Since computers often organize millions of bits of information, computer programmers strive to create efficient algorithms that will perform a task in the fewest number of steps. The previous activity demonstrates that instructions must be clear. This activity demonstrates that there can be several sets of instructions that accomplish the same task-searching for a number.

Students act out two search methods. One is simple, but usually slow. The second is more complex, but usually fast. The first program checks each member of the group in sequence to see who has the designated number. In a group of one million members, you would need on average 500,000 checks to find one member. In the second search method, the group is halved at each step. Finding a single member in a group of one million will take at most 20 checks.

Computer search algorithms are used every time you "spell check" a report or call directory assistance for the telephone number of your favorite restaurant.

Objective

• demonstrate that there are different methods (algorithms) for accomplishing the same task, and that different methods have advantages and disadvantages such as simplicity, accuracy, and speed

• Ask for one volunteer to be the searcher.
• The other members of the group each take a card with a number from 1 to 15 and line up in numerical order (see diagram).
• Randomly pick a number from 1 to 15 for the searcher to look for. Write it on a piece of paper for the searcher to carry.

• The searcher goes to the first person in line. He compares the number he is searching for with the number of that person.
• If the numbers are equal, he has found the number. If not, he moves on to the next person in line.
• Count how many steps it takes to find the matching number.

Search method 2:

• The searcher goes to middle person in line, number 8. She compares the number she is searching for with 8.
• If her number is bigger than 8, she discards everyone with numbers less than 8. If her number is smaller than 8 she discards everyone with numbers greater than 8.
• The searcher then repeats the step and compares her number to the middle number in the remaining group.
• When the number is equal she has found the match.
• Count how many steps it takes to find the matching number.

• Repeat the search a few times, with searchers looking for different numbers. Compare the two search methods.
• Which method would you prefer if the numbers were scrambled?

(For these procedures assume there are two groups of 15 people.)
• Write the numbers from 1 to 15 on two sets of cards.
• Shuffle the cards.
• Hand out a set of cards to each group and have each group form a line in random order.
• At the word go, one line should reorganize itself in sequential order. As soon as the line is organized the searcher starts at one end and begins looking for a match using the second search method.
• The other line remains in shuffled order and at the word go, the searcher starts at one end and begins looking for a match in sequential order using the first search method.
• Which method works faster? Is it always the same one?

Materials
battery
battery holder
bulb
bulb holder
foam trays
wire or aluminum foil
metal fasteners (brads)
masking tape
scissors
quiz board templates

Background for Instructors
Inside computers, telephones, VCRs, and many other electronic machines are boards with electrical components mounted to form circuits. These circuit boards channel the flow of electrical signals through the machine.

In this activity campers construct circuit boards using short strips of wire or foil hidden behind a tray to connect metal brads. When the matching brads are connected with wires to a battery and bulb, a circuit is completed and the bulb lights. Campers can then use their circuit testers as "quiz boards" to find matching pairs.

This activity makes more sense if campers have already constructed working battery, wire, and bulb set-ups. If, due to logistical constraints, some participants are making their circuit boards prior to experimenting with circuits, it may be helpful to set up some circuit "testing stations" ahead of time.

You can use the sample "quiz" sheet included here or campers can use the blank template to create their own quiz questions. Try matching sports teams with their cities, or words in English with words in Spanish, or animals with the foods they eat. It is helpful to have a template showing where to insert the brads.

Objectives

• construct a circuit board with multiple paths along which electricity can flow
• demonstrate how switching current on and off can represent information (in this case a correct match)

Procedure

• Each person needs a foam tray, wire or aluminum foil strips, 10 brads, scissors, and tape.
• Tape a paper quiz sheet to the outside, bottom of the tray.
• At each dot along both sides of the quiz board insert a brad.
• Attach a strip of wire along the back of the tray between the brads of a matching pair. For example, connect the invention to the year it was invented. Be sure the wire is securely wrapped around the end of the brad. Tape over the wire, being especially careful to cover any exposed metal. (This will prevent the accidental creation of multiple current paths between two points.)
• Repeat for each set of brads, carefully taping the ends each time.
• Test for complete circuits by touching the two loose wire ends of a battery and bulb set-up to any two brads. If there is wire completing the circuit between the brads, the bulb will light.

Footnotes
[1] The Computer Museum Network. Education Activities Packet. http://www.tcm.org. 1996.
[2] AAAS. pp. 18, 201, 202.
[3] Adapted from How Things Work. Neil Ardley. 1995. pp. 174-175.