Chapter 1 : Computer systems

Chapter 1 : Computer systems

1. Computer: an electronic programmable data processing machine

   • Computer system: a collection of hardware and software that works together to achieve some data processing task
     • Hardware: Physical components such as keyboard, mouse, printer etc
       • Input devices recieve data from the outside and convert it into signals that the computer can process
       • The CPU processes these inputs and performs calculations by fetching and executing program instructions
       • Output devices output the results of processing to the user
       • The data may be stored for later use or transmitted to another computer system
     • Software: The programs including the operating system and any application software (spreadsheets etc)

2. Importance of computer systems

   • business: Improved/cheaper quality of manufacturing (robots)
   • communication: faster access to information, mobile phones etc
   • entertainment: games, books, movies, music
   • safety: monitoring power stations
   • education: can learn from anywhere. Maintain grade/register information
   • Reliability in computer systems is needed in many life or death situations
     • Aircraft navigation and control
     • Railway signalling
     • Medical situations
       • diagnosis
       • record keeping
       • remote surgery
     • If systems are not reliable then it can cause problems such as:
       • data loss
       • expensive errors
       • privacy issues
     • Reliability can be improved by testing
       • time consuming
       • expensive
       • difficult to do
   • Data integrity means that data being accurate and reflecting reality
     • Data integrity can be compromised by
       • Innacurate data entry
       • software bugs
       • viruses
       • natural disasters
     • To reduce risks
       • backup data regularly
       • control access to data
       • use validation rules

3. Standards (conventions/rules)

   • Standards are important because
     • Help minimise waste
     • Promote common ways of working
     • Enable different equipment to work together
   • Programming standards make it easier for programmers to work in teams and modify other people's programs
     • Giving variables sensible names
     • Comments to explain the code in plain english
     • Indenting the code to make it more readable
   • Professional standards
     • Defacto standards develop over time because of common usage e.g. Microsoft Word was not the only word processing program, but now most people use it by choice
     • Proprietary standards are ones that are set by an organisation. E.g. all Apple products must conform to Apple's rules
     • Industry standards are set and maintained by non-commercial organisations and are available to anyone (e.g. USB or SD card)
     • Open standards are publicly available and flexible. You do not have to pay to use these standards and can be modified.

4. Ethical and legal issues: Computer systems can be used for good and bad purposes. Ethical acts are morally 'right'

   • Legal issues
     • Data protection act: Law to protect data from being used unlawfully
       • protect data from unauthorised access
       • only collect data for a specified purpose
       • don't keep data longer than necessary
       • keep data accurate and up to date
       • don't store data outside of Europe (law)
       • allow people to view information stored about them
     • Computer Misuse Act: Makes logging in or modifying someone elses accounts illegal (viruses/hackers)
     • Copyright designs and patents act: It is illegal to make a copy of a publication without gaining permission from the copyright owner
     • Heath and safety at work act: Makes employers respobsible for the wellbeing of their staff (trip hazards, chairs etc)
   • Environmental issues
     • Bad
       • The production of computers requires raw materials as well as energy
       • Computers require energy to run
       • Old computers are not easy to dispose of (they contain nasty chemicals) and not reused as much as they could be
     • Good
       • People can work from home meaning less travel
       • Less ink wasted printing
       • Processes can be more efficient and therefore less wasteful
   • Ethical issues
     • Terrorism
     • Data security
     • Would it be ethically right for a government to store all data about its citizens?
     • Is is right that some people have access to computers/the internet and some don't?
     • Is it ethical to use cheap labour in foreign countries

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