1 Computers and processors: introduction
Computers have become a vital part of everyday life. It is almost inconceivable that you could spend a day without at least one event being influenced by a computer. Perhaps the word ‘computer’ automatically conjures up the image of a personal computer sitting on a desk, but in fact it is the computers you cannot see that influence your life the most. Typical examples of common products that may use these ‘invisible’ computers are:
bar-code reading systems
This is a very short extract from a very long list, but even this limited set of examples shows how significant the use of computers has become. Without computers many everyday products such as mobile phones would not exist, dramatic progress in the development of products such as artificial limbs could not have happened, and you would not have the luxury of many conveniences now taken for granted, such as email.
The computers which form the basis of those used today were mainly developed in the 1940s. The following quote taken from that era shows how difficult it was to conceive of the way in which computers would develop in the following decades.
I think there is a world market for maybe five computers.
(Thomas Watson, Chairman of IBM, 1943)
Even later on, in the mid 1970s, some still failed to comprehend the size of the future computer market.
There is no reason for any individual to have a computer in his home.
(Ken Olsen, President of Digital Equipment Corporation, 1977)
And although a diminution in size was anticipated, it was considerably underestimated.
Where a calculator on the ENIAC is equipped with 18 000 vacuum tubes and weighs 30 tons, computers in the future may have only 1000 vacuum tubes and perhaps weigh 1½ tons.
(Popular Mechanics, March 1949)
Figure 1 shows a picture of the ENIAC computer mentioned above. You can see it is rather larger than the personal computer available today! Completed in the US in 1945, it was one of the earliest electronic computers. Its name stands for Electronic Numerical Integrator And Calculator, and it was designed to calculate ballistic firing tables in the Second World War. It could perform mathematical operations such as addition, subtraction, multiplication and division, and it could find square roots and compare two values for equality.
As part of the ENIAC fiftieth anniversary celebrations, students and staff at the University of Pennsylvania fabricated a version of this computer using modern manufacturing processes. The component at the heart of this later version measures 7.44 millimetres by 5.29 millimetres! A personal computer was connected to this component to provide the modern equivalent of the cable connections shown on the left hand side of Figure 1 and display the ENIAC's outputs.
Computers like ENIAC were built because of the need for powerful automatic calculators. Another famous use for an early computer was the work at Bletchley Park in the UK to break the German diplomatic codes used in the Second World War.
A computer is a machine that manipulates data following a list of instructions that have been programmed into it. Input devices are used to input data into a computer; the keyboard of a personal computer, the scanner of a bar-code reading system and the switches or buttons of a microwave oven are some examples. The list of instructions the computer follows is called a computer program. So, for example, a QR code reader on a mobile phone app sends the name of a scanned bar-coded product and product details to the phone. The app has been programmed with a set of instructions that makes it:
take in data via the QR-code scanner;
use the data from the QR-code scanner to look up the name of the product in a list that cross references QR-code data to product name;
generate a new form of data that is compatible with showing the product name and image on the display;
In this example the screen is being used as an output device. There are many different types of output device. The actuator that switches on a pump of a computer-controlled central-heating system is one example; the sound system that generates the beep of an electronic heart monitor is another.
I have used the word ‘data’ several times now in the context of the computer receiving input data, generating data and outputting data. A computer can only work with information that is presented to it in a very strictly controlled format. When information is in this format it is called data. Quite simply, a computer cannot perform its task if the information it needs has not been transformed into the required data form. You will find out more about the format of data a computer needs later on in this block.
As computers have developed, a critical change in their role has been their use in communication: many of the applications that run on personal computers (PCs) and mobile phones help us communicate with each other, and also with other computers. The following quote from Danny Hillis, a pioneer in the development of some of the fastest and most powerful computers, gives some insight into how computers can turn everyday objects into part of a communication system.
I went to my first computer conference at the New York Hilton about 20 years ago. When somebody there predicted the market for microprocessors [these are the major component of all computers] would eventually be in the millions, someone else said, ‘Where are they all going to go? It's not like you need a computer in every doorknob!’ Years later, I went back to the same hotel. I noticed the room keys had been replaced by electronic cards you slide into slots in the doors.
There was a computer in every doorknob.
(Danny Hillis, circa 1999)
Of course you do not know exactly the configuration of the computers in the doorknobs of the Hilton; it could be that they simply verified that the card should give the holder access to that particular room. Alternatively the doorknob computer could communicate with another computer, telling it that the occupant had just entered the room. This second computer could then ring the telephone to pass on any recorded messages, activate a display showing if the occupant had received any e-mail or perhaps run the bath!
As you study this course you will find out how computers and the components within them carry out their allotted tasks, and you will also develop an understanding of how improvements in computer technologies have allowed computers to become smaller, more powerful and cheaper.