Student notes 1. Computer systems. Characteristics of a computer system

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1 Student notes 1 Computer systems Characteristics of a computer system This course is not just about computers. It is about computer systems. You may have a computer inside your classroom or at home. Possibly, it looks something like this: Let s consider some aspects of this computer. It has input devices, such as the keyboard and the mouse. These input devices allow the person who is using the computer to enter data, for example a story he or she wants to write, or some numbers to calculate. When the data is entered it is converted into a special format called binary code. (You will study exactly how this is done in Section 4.) Binary code uses only the digits 0 and 1 to represent all types of data that are entered into the computer. After the data is entered, it is stored in binary code in storage devices. This may be stored only for a very short time in the memory of the computer, or it may be stored on a disk or USB drive to be used later. The computer can process the data. It performs a number of operations on the data to achieve a desired result. For example, it can perform calculations on numbers that have been entered, or it can convert a piece of written text to speech. The computer also has output devices so that users can see the result of processing the data. The output device converts binary data in the computer to a form that the user can understand such as images on the screen, a print out or sound. The computer can also communicate with other computers, for example over the internet. When it does this the data is sent between the computers in binary code. Page 1 of 6

2 Different kinds of computer systems A desktop computer such as the one shown above is not the only type of device which can be called a computer system. Consider this smart phone: Just like the a computer It has input devices : the keypad and the microphone. When you press a number or you speak into the microphone, what you input is converted into binary code. The binary code is stored in the phone s memory, or if you want to keep it for longer it may be stored onto a memory card on the phone. The phone processes the data, (e.g. by converting multiple presses of a key into letters). The phone displays what it has processed on the image on the screen. The phone can also communicate with other computers in binary code. For example, if you type in a text message, it will be sent in binary code via the telephone company to your friend s phone. Your friend s phone can then use an output device to display the message. The mobile phone can be seen as just a very specialised computer. This is the same for many other devices, such as MP3 players, digital television sets, satellite navigation systems etc. In this course, although we will often be talking about computers, we study all kinds of computer systems. What they have in common is that they all work by processing digital data and have a series of devices that allow this data to be input, output and communicated to other computer systems. Page 2 of 6

3 Importance of computer systems Over the last thirty years, computers have developed considerably so that they are now essential to any modern society. Personal computers become a much more common item available in most homes as well as in public places such as schools and libraries. Computer technology is also being used in an increasing number of devices and many devices have been improved through the use of this technology. One major development in computer technology is the internet. The number of people who connect to the internet increased significantly over the last twenty years. The speed at which people can access data through the internet was also increased. People now connect to the internet not just with computers, but also with many different types of devices, such as mobile phones, television set-top boxes and electronic textbooks. As the internet becomes bigger, better and faster, people are finding more and more uses for the possibilities it offers. A major use of computer technology and the internet is in education. Several new tools have been produced to help students and others learn better. Electronic teaching materials, such as the one you are using at the moment, offer several advantages over traditional textbooks. The classroom has also been transformed by the use of technologies such as electronic white boards and interactive voting systems. There are computer systems such as virtual learning environments (VLEs) that help teachers provide teaching materials to pupils and monitor the progress that the pupils are making. The internet contains large libraries of information to assist students with research and people who are connected to the internet have more information at their disposal than ever before. It is important, however, to evaluate carefully any information received from the internet to decide whether or not it is reliable. Computer technology has also had a great impact on people s leisure activities and social lives. Many leisure activities are enhanced through the use of computers, even though this is not always obvious. For example, the planning, marketing and selling of tickets for events such as football matches or rock concerts often rely heavily on computer technology. At the events themselves, computers are used to manage the technical aspects of the events, such as lighting or display boards, in a much more effective way than when this was done manually. Computer-based gaming is now a large part of many people s leisure activities, and this is increasing more as new types of gaming platforms and new genre of games emerge, engaging different parts of the population. The connectivity of the internet has enhanced this even more, allowing people to engage with others in a variety of ways. Social networking sites, in particular, allow people to connect to each other in new ways. Computer technology has also affected the way that people do business. Most businesses now use the internet in some way in marketing and delivering their products and services to their customers. Through the use of credit cards and online payment methods, more people are shopping online. Although this cannot quite replace the experience of seeing and touching the product in a shop before you decide to buy it, it has provided new Page 3 of 6

4 opportunities as customers and shops do not have to be located near each other. Shops can sell to more customers, possibly across the whole world, while customers have more choice and can look for the best deal, all with the convenience of doing so from their own home. Reliability and standards in computer systems As computer technology becomes more and more prevalent in society, it also becomes more important to ensure that this technology is reliable. Modern society relies a great deal on technology and it is unlikely to function correctly without it. Imagine, for example, that when you woke up one morning and all computer systems have stopped working. You would not be able to listen to the radio or watch TV over breakfast, because even if you have an older analogue receiver, the stations use computer technology to record and transmit their broadcasts. If you go to school by car or bus, traffic would be a nightmare because the traffic light systems are controlled by computers. When you arrive at school, you would find that those teachers who have managed to get into work might not be able to deliver the lessons they planned as many rely on work which is on the computer. Therefore individuals, companies and governments put a lot of effort into making sure that systems do not fail. Data is backed up regularly so that if it is lost or damaged, the backup copy can be used to restore the data. Many people build in redundancy in systems. This means having more computer resources than is actually needed so that if some of it goes wrong, the rest can still carry out all the work that needs to be done. For example, a bank could have its main data stored on two different servers in two different towns so that if anything happens to the computers in one locations, the business of the bank can still run smoothly from the other computer. One way of ensuring that computer systems remain reliable is to insist on high professional standards when they are developed, used and maintained. Companies who make computer hardware and software have to agree to certain standards if they want their products to work with each other. Also, to ensure a higher quality product, companies must set high standards within themselves. They usually have to work as a team, and this means that they must be able to rely on each other and understand each other s work. Users of computer systems also have to keep certain standards. This is obviously true of employees of companies and public bodies because any failure of their systems can lead to the loss of a lot of money, or significant damages to a lot of people. There are therefore a number of rules that such organisations have to follow, such as the Data Protection Act (which we look at in the next section). Computers that are connected to the internet are at risk of being targetted by viruses and other harmful software, so organisations have a responsibility to ensure that they take enough protection against these threats. Even private users have a responsibility to protect themselves, because if they allow themselves to be attacked by viruses, they can then potentially infect other people they contact over the internet. Page 4 of 6

5 Types of standards Standards refer to conventions and rules. They are normally defined by a responsible organisation. There are various categories of standards. In computing, standards exist for programming languages, operating systems, data formats, communications protocols and electrical interfaces. Standards are important because they: enable equipment from different manufacturers to work together make learning new systems easier because they have similar characteristics minimise waste help to ensure fair play and access to markets bring costs down by opening markets to competition. De facto standards These have developed from common usage and include such standards as postscript, the QWERTY keyboard and the Microsoft Word file standard. De jure standards This means by law. They are de facto standards that have become so universally accepted that they have to be adhered to in order for devices and software to be able to communicate. They include examples such as wireless , TCP/IP, ASCII and Unicode. Proprietary standards These are standards owned by an organisation. They ensure compatibility between the company s products. They can also be used to exclude others from competing with rival products. For example, Apple computers lock users into using Apple software. Industry standards These are set by industry-wide organisations, for example: ANSI (American National Standards Institute): this sets standards for some programming languages IEEE (Institute of Electrical and Electronic Engineers): this sets standards for electrical interfaces, such as the RS232 serial interface ITU (International Telecommunication Union): this sets standards for communication protocols ISO (International Standards Organisation) Open standards Open standards are publicly available standards that are often agreed by a group of collaborators and are not for profit. Examples include HTTP, HTML, WAP, TCP/IP, XML and SQL. Page 5 of 6

6 Ethical, environmental and legal considerations As we saw in the previous section, it is necessary to consider right and wrong when making, buying and using computer systems. We now look into this in more detail. Ethical considerations are about what is morally right and wrong. It comes down to what people or society believe is right and wrong. For example, for many people, whether or not you should use open-source software is an ethical issue. They believe that people should not own intellectual property but that it should be made available for everyone to benefit from. Another possible ethical issue is whether school children should be banned from accessing their private or social networking sites in lessons or whether very young children should be allowed to have mobile phones. These things are not illegal in themselves, but many people have very strong beliefs about whether they are right or wrong. Environmental considerations are about what is good or bad for the environment. People are increasingly aware of the fact that the Earth has limited resources and that these should be used carefully. Computer technology does use considerable resources. The components that are used to make hardware devices usually contain plastics which are derived from oil, and metals which are very harmful to the environment if they are not disposed of carefully. It is therefore important to consider how these materials are obtained and recycled. Also computers need power to run and this raises several issues that affect either the manufacturer (such as how to design computers so that they us less power) or the users (such as whether computers should be left on or on standby when not being used). Legal considerations are about what is legal or illegal according to the law of the country. Each country has its own laws and computer systems developers must be aware and abide by them. For example, in the UK, the Computer Misuse Act makes it illegal to hack into another person s computer system to access information that one is not authorised to access. It also makes it illegal to deliberately damage another person s computer system by introducing a virus in it, for example. The Data Protection Act gives clear guidelines on how organisations should obtain and process personal data of real people. For example, if an organisation wants to obtain people s personal data, they must have a clear purpose for doing so, obtain only the data that is necessary for this purpose and use it only for that purpose. It would be illegal for your school to ask you to fill in a form about the leisure activities of your family, and then sell this data to other companies without your permission. This is because this data is not needed for the purpose of educating the pupils and giving the data to another organisation without your permission is illegal under the Act. Apart from laws that are specifically about computers, like the Computer Misuse Act and the Data Protection Act, there are other legal considerations because computers can be used as a tool to commit other illegal acts such as fraud or inciting hatred. It is important to note that ethical, environmental and legal considerations are not always separate things. Countries usually pass laws because the majority of the people in that country believe that something is ethically wrong and should be made illegal. Most people believe that the environment should be protected and so they believe that environmental issues are also ethical issues. Governments, therefore, often pass laws that also affect the environment, such as making it illegal to dispose of batteries in a land-fill site. Page 6 of 6