Input, process, store, output

COMPUTING

Intelligence is skill in a media.

Olson

INTEGRATED CIRCUITS

Many modern appliances contain integrated circuits. An integrated circuit is a semiconductor circuit with many electronic parts. It is usually made on a razor thin slice of silicon with an area of about 0.5 cm2 and a thickness of 0.16 cm. The tiny silicon wafer with its integrated circuit is called a chip. A chip is made by coating a thin slice of silicon with a layer of glass. Glass is an insulator. A second coating of a light sensitive material called photoresist is added. Tiny masks containing drawings of the circuits are placed on the wafer. Exposed to ultraviolet light, the photoresist hardens into the proper outline of the circuit. Areas not exposed are washed away in an acid bath. The acid etches through to the silicon. Another semiconductor material is then added to the exposed channels. More levels are added in the same way to this first level. An aluminum coating that is also engraved with a circuit is the final layer. Under a microscope, the features of a chip appear like the streets, parks, playgrounds, and buildings of a city seen from an airplane.

The integrated circuits on the circuit board are the five rectangular-shaped objects along the top of the photograph. Note that this circuit board also contains transistors and resistors. A close-up of an integrated circuit is shown on a semiconductor chip.

A chip is sealed in a protective case made of plastic or ceramic. Electricity flows in and out of the integrated circuit through wires that connect to prongs on the outside of the case. These prongs are made so they plug into other circuits. An integrated circuit may contain thousands of microscopic size transistors and thousands of electronic switches.

Examples of devices that use an integrated circuit are a digital watch, pocket calculator, and microcomputer. In some microwave ovens, an integrated circuit is used to regulate the timing and operation of the oven. An integrated circuit is used in some cars to regulate the burning of gasoline. Also, integrated circuits are used to regulate the operation of some heating systems.

Integrated circuits have advantages over ordinary circuits. Their small size has made it possible to produce calculators the size of credit cards. Radios are now the size of note pads. An electronic computer uses electric circuits and pulses of electricity to do calculations. A computer is made up of a number of different electronic circuits. So far we have considered the logic circuits for such functions as encoding and decoding of information, parity testing, word comparison, addition and subtraction of binary numbers. These functions are concerned with decision-making. A computer additionally needs to be able to store information in binary patterns. The main storage of a computer is called the memory.

Computer storage circuits, made from transistors or their microelectronic equivalents, can be built to store binary digits as low or high voltages.

A computer that once filled an entire room has been redesigned with integrated circuits to sit on a desktop. Integrated circuits are durable and long lasting. They do not contain any soldered wires. Further, they are economical in use because they operate on low power. Because integrated circuits are tiny, their electronic pathways are very short. Thus, their functions are performed in less time than with regular circuits. Chips made to store huge amounts of information are called memory chips. Another kind of chip, the microprocessor, combines memory and control circuits to regulate computing operations. Simply stated, a microprocessor is a «computer on a chip».

MICROPROCESSOR

The microprocessor is an integrated circuit which has the properties and fulfils the role of a complete central processing unit of a computer. This means that the circuit does not just react in a fixed, pre-programmed way to an input signal to produce an output signal. The main feature of the microprocessor is that its response and its logic can be altered. In other words, the microprocessor can be programmed in different ways rather than react in one pre-programmed way only. (The set of instructions the computer follows is called a program).

For logic and systems designers the appearance of the microprocessor brought with it a dramatic change in the way they employed electronics. They could now replace all those rigid hardwired logic systems with microcomputers because they could store program sequences in the labyrinthine circuits of the memory chips instead of using individual logic chips and discrete components to implement the program. Engineers could thus substitute program code words for hardware parts.

It took about three years before the first devices reached the market but in the meantime about a hundred different microprocessors had become available. As with all microelectronic products, the capabilities of microprocessors advanced rapidly and the sophistication of circuits increased day by day.

INPUT, PROCESS, STORE, OUTPUT

There are four steps that any computer uses in doing its job. These are (1) inputting of data into the computer, (2) processing of the data that has been input, (3) storage of data, and (4) production of some kind of useful output.

In business computers, this four-step process is very easy to see. In order to produce a bill for a customer, we would have to input the information about what the customer bought. Once all of this information had been input, the computer would process this information and would print the information for the customer's bill. Throughout this cycle, the computer would be storing the data that had been input, the data produced during intermediate processing steps, and the data being printed out. Apart from processing data, computer systems are being increasingly used to store data; such storage has the advantage of allowing data to be rapidly retrieved.

In manufacturing, computers are used to control robots. If you think about it, any robot has to use some sort of a computer as the basis for its «intelligence». If we were to build a robot to be used in the assembling of automobiles, and if our robot had the specific task of mounting wheels on the car, the instructions for this process would be input into the computer. In addition, the robot would still have to be able to determine where the car and the wheel were. Various types of sensors, such as a television camera, would enable the robot to «see» the position of the wheel and the car. In this case, we would not have to type information into a computer for the robot to act. We do have to have some means of getting the data into the computer, like a television camera. If we were to build this robot correctly, it would use the television camera to tell where the car was, where the wheel was, and even where the lug nuts were. The television camera would be the input. The process would be the calculations required to determine how to get the wheel on the car, and the output would be the robot's response to these calculations: mounting the wheel on the car, putting on and then tightening the lug nuts, and checking to see if the tire were properly mounted. The basic steps - input, store, process, and output - would be taking place with our robot even though no data was typed into the robot's computer (remember that the instructions had been input earlier, and were being stored). The sequence of input, store, process, and output takes place no matter what kind of computer we use.