Fundamentals of Computer Systems

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Computer Systems

Candidates should be able to:

  • define a computer system
  • describe the importance of computer systems in the modern world
  • explain the need for reliability in computer systems
  • explain the need for adherence to suitable professional standards in the development, use and maintenance of computer systems
  • explain the importance of ethical, environmental and legal considerations when creating computer systems.

This topic introduces computer systems and provides a foundation for the remaining topics in this unit. Candidates should develop a mental model of a computer system which comprises hardware and software and in which:

  • data is input and converted into the computer’s internal representation by input devices
  • the data is processed
  • the results of the processing are converted from the computer’s internal representation and output by an output device
  • the data may be stored for later use or transmitted to another computer system while it is still in the computer’s internal
  • representation.

What is a computer system?

  • A computer system is made up of hardware and software components and is capable of:
    • data input – using input devices
    • data processing – using a microprocessor, typically the Central Processing Unit (CPU)
    • data output – using output devices
  •  It may also be capable of:
    • data storage – so data can be stored for later use
    • data transmission – so data can be transferred to or from another computer system

As well as the personal computer, this definition applies to any equipment which uses computer technology.


What is hardware?

Hardware refers to any component that has a physical presence and can therefore be touched. Hardware devices can be divided into five types:

  1. Input Devices – these include any kind of device which can be used for getting data into the computer system from the outside world. Some examples include; keyboard, mouse, microphone, heat sensors, switches, touch screens, digital cameras and so on.
  2. Processing Devices – this usually refers to the Central Processing Unit (CPU) which carries out program instructions.
  3. Storage Devices – these include any device which will store data until it is needed for processing. This can include temporary storage devices, like the computer’s memory, or long-term storage devices like hard-drives, DVD drives or tape drives, etc.
  4. Communication Devices – these deal with the transfer of data from one computer system to another and include routers which link networks and modems which allow computers to communicate data via the Internet.
  5. Output Devices – these include any devices which can provide data in a useful format to a user. For example a computer monitor, speakers, printers etc.

The diagram below gives some examples of these different types of device. The arrows show how data can be transferred between them in a computer system.

Fundamentals of Computer Systems Image 1
Typical hardware components and how they are linked

Peripheral Devices are hardware devices which fit into one of the above categories but are external to the main body of the computer. They are typically connected by cables (USB, network, firewire etc.) or wirelessly (Bluetooth, wireless network links etc.). Examples include keyboards, mice, scanners, printers, external hard-drives etc.


What is the importance of ethical considerations when creating computer systems?

  • Employment – computer systems often either replace jobs directly (automated production lines, warehousing etc.) or lead to improvements in efficiency which can lead to job losses.
  • Monitoring – network technicians can log what software users have accessed, what web sites they have visited and can access a user’s files and even view their email on some systems. Should such personal information be monitored and if it is monitored, who should have access to it?

What is the importance of environmental considerations when creating computer systems?

One of the main environmental considerations when creating computer systems is weather to upgrade an existing system or replace it with a new one.

Environmental advantages of installing a new system:

  • Power consumption – Modern computers tend to be smaller and more efficient, as well as having better ‘sleep’ systems so they use far less power when not in use. Modern computer systems usually include a LCD monitor which have 1/5 the typical power consumption of older cathode ray tube (CRT) monitors.

Environmental disadvantages of installing new systems:

  • Use of resources – one study suggests that making the average PC requires 10 times its weight in chemicals and fossil fuels. Compare this to cars or refrigerators which require 1-2 times their weight.
  • Health risks – discarded computer equipment is usually either dumped in landfill sites or recycled, often in poorly managed facilities in developing countries. Some of the hazards include:
    • Lead in cathode ray tubes and in solder.
    • Arsenic in older cathode ray tubes.
    • Antimony trioxide as a flame retardant.
    • Upgrading RAM can be a cheaper option to replacing a computer system
    • Polybrominated biphenyls (PBBs) as flame retardants. in plastic casings, cables and circuit boards.
    • Selenium in circuit boards.
    • Cadmium in circuit boards and semiconductors.
    • Chromium and cobalt in steel.
    • Mercury in switches and housing.

Alternatives to dumping/recycling:

  • Refurbishing/upgrading – this can often be a better option than throwing it away, the majority of computer systems disposed of are far from their real end-of-life and could go on to give as much as 6,000 additional hours of use with motherboard, RAM, CPU and hard-drive upgrades.
  • Sending to developing countries – many charities will ship old computer equipment to countries in the developing world where 99% of children leave school without ever having seen or touched a computer in the classroom.

What are the importance of legal considerations when creating computer systems?

The Data Protection Act

  • Computer systems can hold huge quantities of information and global networks are able to share and distribute this information around the world in seconds. In order to control this development and to protect people’s right to privacy, the Data Protection Act was introduced.
  • Out of the 8 basic principals of the Data Protection Act the following should be considered when creating computer systems:
    • Any personal data on the computer system should be kept secure against loss, damage and unauthorised and unlawful processing.
    • Any personal data on the computer system should not be kept longer than necessary.
    • Any personal data on the computer system should be accurate and up-to-date.

The Computer Misuse Act – 1990

  • Under this law, the following offences are classified as hacking and are illegal:
    • Unauthorised access or attempted access to computer data. This covers any unauthorised access to any program or data held in a computer, even if it is just to look at the information.
    • Unauthorised access to computer systems for the purpose of carrying out crimes – i.e. spying, blackmail, and fraud. This covers cases where someone access the system with the intention of using the information for a criminal purpose.
    • Unauthorised changing of computer data – i.e. deleting or altering files.
      This covers cases where the original information is altered in some way, either by deleting it or altering it in some way. It also covers spreading computer viruses.
  • When a computer system is created it should therefore incorporate security features such as data encryption, firewalls, user ID’s and passwords to minimise the risk of hacking. Anti-virus software should also be installed.

The Copyright, Designs and Patents Act – 1989

  • Unauthorised copying of computer software is a criminal offence. This Act covers unauthorised copying of software (including portions of the code), using illegally copied software and manuals, and running purchased software on more machines than the license allows.
  • When a computer system is created all the software used should be fully licensed, including the operating system, utility software and application software.