Diferencias interindividuales en la prevalencia de la antipatía en grupos de población minoritarios 1

Mini case 3.2

Personal computers

In August 2000 Lou Gerstner, the chairman and chief executive of IBM, declared ‘The personal computer is dead.’ The warning sounded absurdly exaggerated, but it does reflect the evidence that although sales of PCs are not actually falling, the rate of growth in sales is slowing.

There are a number of reasons for the slowdown. One problem is that most con-sumers who want PCs already own one, certainly in economies such as the USA. There is a real concern that the PC market may be reaching saturation point. In the past, sales have been pushed by PC users upgrading machines every three years or so as ever more sophisticated software was offered that required ever-faster processing power.

Increasingly, the main frustration of home PC users is not their hardware but the speed of their connection to the Internet. What is holding them back is bandwidth – slow access to the Internet. Who needs faster chip speeds when you are using a slow 56K modem?

Companies are also becoming more reluctant to keep upgrading PCs in the office.

They are increasingly put off by the loss of productivity involved in deploying new technology. PC makers have reacted to the slowdown with a variety of strategies, including designing sleeker models and monitors in various translucent colours. Others are placing more emphasis on hand-held machines. Moves into new markets are extra-ordinarily difficult to execute. Very few of the mainframe makers succeeded in mini-computers, hardly any minicomputer makers moved successfully into PCs, and almost none made it from PCs to laptops. The record of transition is dismal.

The power of the desktop computer has been further enhanced by the development of local area networks. These link various pieces of hardware, including desktop computers, together in order to communicate with each other and to share resources.

The rapid increase in performance and decrease in price can be seen by consulting Table 3.1. No other form of technology can boast such rapid performance and price developments. If a luxury motor car of the 1940s, for example a Rolls-Royce, had demon-strated changes on the same scale it would cost about a pound sterling, travel at one thousand million miles per hour at ten million miles to the gallon of fuel. It would also be the size of a matchbox yet, paradoxically, have ten thousand times the luggage capa-city of the 1940s’ Rolls-Royce!

Table 3.1 An indicative summary of the effects of technological advance on the performance of computers

Date Generation Technology Number of Storage Cost (for a Average time

instructions capacity typical large between executed per (number of computer) breakdowns

second characters)

1950s 1 Valve 1000 10,000 £5m hours

1960s 2 Transistor 100,000 100,000 £2m hundreds of

hours 1970s 3 Integrated transistor 10,000,000 10,000,000 £4m+ thousands

circuit board of hours

1980s 4 Micro-integrated 1,000,000,000 1,000,000,000 £2m+ years circuit (microchip)

1990s 5,000,000,000 100,000,000,000 £1m+ years

2000s 10,000,000,000 10,000,000,000 £100,000+ years

Many companies that have depended on PC growth for their fortunes are now wondering what they will have to do to prosper in a new era of technology. The PC may not be dead but, with the outlook for sales growth uncertain, these are danger-ous days.

Adapted from: Speeding to a halt Financial Times: 1 December 2000

Questions

1. Why has the chairman of the company that pioneered the introduction of the personal computer now stated that the personal computer is dead?

2. What factors are making companies reluctant to upgrade their office computers?

3. Carry out some research to provide evidence of the difficulty for computer manufacturers to transfer into new markets.

3.2 Hardware

The terms ‘hardware’, ‘software’ and ‘firmware’ occur frequently in any literature con-cerned with computers. It is important at the outset to have some understanding of their meanings:

n Hardwareis the physical components in a computer system. Circuits, keyboards, disk drives, disks and printers are all examples of pieces of hardware.

n Softwareis a set of instructions, written in a specialized language, the execution of which controls the operation of the computer. Programs are examples of software.

n Firmwareis the permanent storage of program instructions in hardware. It is usu-ally used to refer to a set of instructions that is permanently encoded on a microchip.

The term ‘firmware’ is used because it is the inseparable combination of hardware and software.

3.2.1 Functional components of a computer system

A computer system is a system that accepts data as input and produces information as output. Information, as will be recalled from Chapter 1, is data that has been processed to serve some purpose. In producing this, the intermediate products of this process may be stored. The process of transformation of inputs into outputs is carried out by elec-tronic circuitry. The process is controlled by a sequence of instructions – the program – that is stored in the computer.

Computer systems fit the common systems model explained in Chapter 1. Figure 3.1 illustrates the basic organization of a computer system.

1. Input:The purpose of the input component of a computer system is:

(a) to accept data in the required form;

(b) to convert this data to a machine-understandable form;

(c) to transmit this data to the central processing unit.

Examples of input devices to be explained later are keyboards, magnetic ink char-acter readers, bar-code readers, optical charchar-acter readers and the mouse.

2. Central processing unit (CPU): This is made up of three components: the control unit, the arithmetic and logic unit, and the main memory.

(a) The purpose of the control unit is:

– to decode and execute the program instructions one by one;

– to control and coordinate data movements within the CPU and between the CPU and the other components of the computer system.

(b) The purpose of the arithmetic and logic unit (ALU) is:

– to carry out arithmetic operations – for example, to add two numbers together;

– to carry out logical operations – for example, to compare two numbers to establish which is the larger.

(c) The purpose of the main memory (synonyms – fast memory, immediate access memory, core store, direct access memory) is:

– to store programs during their execution;

– to store data that is being used by the current program;

– to store the operating system (this is an important program in the control of the computer; details are covered in a later section of the chapter).

Currently, the main form of hardware for carrying out the functions of the central processing unit is based on the microchip.

3. Secondary storage (backing store):The purpose of secondary storage is:

(a) to maintain a permanent record of data and programs when not being used by the CPU;

(b) to maintain a store for the program and data currently being used if the main memory is not large enough to accommodate the entire program and data;

(c) to maintain a copy for security purposes of data held in the main memory;

(d) to act as a secondary input/output device when the input is in magnetic form or the output is required in magnetic form.

Figure 3.1 Functional components of a computer system

Examples of secondary store hardware to be covered later are magnetic and optical disk devices, magnetic tape machines, and tape streamers.

4. Output:The purpose of the output component of a computer system is:

(a) to accept information/data from the CPU;

(b) to convert this information/data into the required output form.

Examples of output devices are printers, monitors, machines for producing com-puter output on microfilm and voice synthesizers.

In the next sections, each of these functional components is treated in some detail. In particular, the various ways in which each may be physically realized in a modern com-puter system are explained and evaluated.

3.2.2 Input devices, media and data capture methods

The purposes of input devices are:

n to accept data in the required form;

n to convert this data to a machine-understandable form; and

n to transmit this data to the central processing unit.

Keyboard

The most common keyboard device used is the QWERTY keyboard. It is called a

‘QWERTY’ keyboard because these are the first six letters on the top left of the key-board. The keyboard is derived from the old typewriter standard to which some extra keys have been added for specific computer-based functions. Unfortunately, the stand-ard typewriter layout was not designed to be the most efficient from a data input point of view. Rather, the key layout was organized in the nineteenth century so that old mechanical typewriters were least likely to jam when typing occurred. Modern com-puters and electric typewriters do not suffer from this deficiency and so the standard is outmoded. Keyboards have been designed that allow a trained typist to input text at the rate of about 180 words per minute. This compares with the QWERTY norm for an input of about sixty words per minute. Why are all standard typewriter key-boards based on this old-fashioned inefficient layout? The answer is partly to do with inertia in the computing industry but also because there is now a huge investment in QWERTY-based equipment and QWERTY-trained staff. This does not make it feas-ible, in the short run at least, for any organization to change.

Key presses are converted into character code consisting of bits (binary digits) which can be either 1s or 0s. There are a few internationally recognized coding systems for computers. The two most used are the American Standard Code for Information Interchange (ASCII) and the Extended Binary Coded Decimal Interchange Code (EBCDIC). The former code is most commonly used for desktop computers and data communications. The EBCDIC code is used in IBM mainframe computers. Within a coding system, each different keyboard character is coded as a separate binary string.

For instance, in the ASCII 7-bit code C is coded as 1000011.

Keyboard data entry is almost invariably accompanied by a monitor or screen on which the characters input to the keyboard are displayed.

Using a keyboard for data entry is common to a wide range of applications. They fall into three main categories:

1. The entry of data from a source document such as an invoice or an order. Controls must ensure that all the data is copied correctly and completely. Data entry con-trols are covered in the later chapter on concon-trols.

2. Interactive use of the computer by a user. Here there is no source document but the user is inputting commands or queries into the computer system.

3. The entry of text data, as in word processing.

Advantages: Keyboard data entry has a number of advantages over other forms of data input:

n There is a low initial cost for purchase of the equipment.

n The method is extremely flexible as it relies heavily on the person entering the data.

People are flexible.

Disadvantages: There are also a number of disadvantages:

n For efficient use, training of personnel is needed.

n It is a slow form of data entry. People are slow.

n It is costly in operation as it relies on people. People are expensive to employ com-pared with the capital cost of equipment.

n Unless there are adequate controls, using a keyboard will lead to high error rates.

People are error-prone.

Where data is input by keyboard, invariably a mouse is used as a supporting device.

A mouse is a small hand-held device about the size of a bar of soap. It contains a ball on its lower surface and selection buttons on its upper surface. As the mouse is moved over a desk the ball-bearing moves and controls the positioning of a pointer (often an arrow) on the monitor. The pointer can be moved to a position on the screen to select an item such as a menu option or position a cursor, such as the text insertion marker (called a caret) in a word processor. Alternatively, in graphics applications, the movement can be used to trace out lines and draw and colour shapes.

Multimedia input devices

n Digital camera: A digital camera is similar in appearance to a normal camera and captures still images. Rather than using photographic film, the images are stored in memory inside the camera and later transferred to a computer. The digital camera has the advantage that pictures of poor quality can immediately be deleted and replaced.

n Webcam: A webcam is similar to a digital camera in that it digitally captures images. Webcams are low-cost devices that are connected to a desktop computer system and usually placed on top of the monitor. Images are not usually stored but are communicated in real time using a local network connection or the Internet to another computer user.

n Video capture:Moving images, from either a digital video camera, a television trans-mission source or a prerecorded video disk or cassette, can be input directly into a computer with a video capture card installed. These images can then be edited or enhanced in a variety of ways and then either stored or output for immediate display.

n Scanner: A scanner is a desktop device used to capture a document image. The document is placed on a glass plate and an image is optically captured by passing

a bright light across the source document. The image is converted into a digital bit-map, an array of 1s and 0s, and transmitted to a computer, where it can be stored in memory and later edited, if required, and saved. A particular application of scan-ning is in optical character recognition, which is described below.

n Voice data entry: Voice data entry consists of the reception of speech data by a micro-phone, the conversion of the data into electronic signals, the recognition of the data and its final conversion into textual form.

A difficulty for the designers of speech recognition software is that two people repres-ent the same word verbally in differrepres-ent ways, the same person represrepres-ents the same word verbally in different ways on different occasions, and two people may speak dif-ferent words in a similar way. There is, however, massive investment in developing voice recognition facilities. This is because the potential financial rewards are great.

These will occur in two main areas. First, the need for typists (as distinct from secre-taries) will disappear. Text will be dictated into a microphone and instantly displayed on a screen for voice-controlled editing. There will be no need for a person to be employed to take down shorthand, which is then converted into printed text for correction.

Hundreds of thousands of typists’ jobs will rapidly disappear. Second, voice data input will enable people to interrogate computers remotely via the telephone system with mini-ature mobile transmitter/receivers connected to the public telecommunications net-work. This will enable the information-providing power of computers to become fully portable. Output might be provided by a synthesized voice or connection to a tradi-tional output device.

Currently, voice data entry systems are already used in telephone-based information provision and order-processing systems. Software for the acceptance of speech that is then turned into text has become more readily available. These programs run on standard PCs and interface with standard word-processing packages. In order to work effectively the user must undertake a period of training on the computer – training, that is, of the computer in order to allow it to recognize the particular voice patterns of the user. This typically takes a few hours. Accuracy rates of 95% with speech input at over 100 words per minute are claimed as standard at the current level of development.

The main advantage of voice data entry then lies in the possibility of remote inter-rogation of computers for information and the preparation of text documents by unskilled personnel rather than in high-volume business data entry.

Mini case 3.3

In document No nos gustamos: las relaciones de antipatía al comienzo de la educación primaria (página 168-181)