Lesson 4
Computer systems
What is a system?
Inputs
Processes
System boundary
Outputs
Computer systems
Examples of a system – can you identify what they are?
Passengers,
electrical
energy
Train
movements
Journeys
Food, oxygen
Oxidation
Energy, CO,
H2O
Enquiry,
deposit
Search,
Make
booking
Tickets,
reservations
Computer systems
 Computer systems are based on processing data and producing
information
 They are programmable.
 Found in most electronic gadgets
 Usually made of Input/Output devices, storage, a processor and
software
 Some computer systems are dedicated. In electronic gadgets
they are known as embedded systems.
 Controlling focus and shutter speed of a camera
 Car cruise control
 Logging a mobile phone onto a network
 Guiding a robot vacuum cleaner around obstacles.
 Some computer systems are general purpose.
Computer systems
 Involved in most human activities – see list on page 10
Reliability
 Need to trust computers, need them to be reliable.
 Unreliable computers
 can have lethal consequences in some situations. Can
you think of any?
 Loss or theft of data – inadequate security systems
 Don’t perform the function they were programmed for.
Computer systems
Testing
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Some programs have millions of lines of code.
Testing is a vital part of development.
Sometimes impossible and expensive to test everything.
So monitoring for the life of the system is important.
Testing is carried out to try and break the system, to show
where its weaknesses are.
 Testing may be done by users – this is called beta testing.
(Alpha testing is done by the developers)
 Testing is done against the specification.
 Some systems are flawed because the specification is bad.
Computer systems
Standards
 Benchmarks and procedures to adhere to, to increase the
reliability of the system.
 Common standards help with compatibility issues between
computer systems
 Proprietary Standards
 Company standards – defined by the software company itself
– e.g. Windows adhering to standards set by Microsoft and
Flash with Adobe.
 Insistence of company standards will:
 Provide a familiar look and feel to the systems
 Make them work in a predicable way
 Allow maintenance through one company.
Computer systems
Standards
 Industry Standards
 Usually relate to hardware such as the USB standard for
interconnectivity between devices.
 De Facto Standards
 Standards that have developed through common usage
 Car layouts
 HTML
 PDF (Originally a proprietary standard from Adobe then
given to the International Organisation for
Standardisation)
 Microsoft Word .doc formats
Computer systems
Standards
 Open Standards
 Standards that are publically available and usually developed
through open source software.
 Updated via a community of developers, usually free
 Usually high quality
 No one to blame if errors
 Examples
 HTML
 TCP/IP
 C#
 Firefox
 Libre Office
 Android
 Linux
 Apache Web Server
 Moodle
 Python
Computer systems
Ethics
 Codes of ethics in the computing world
 BCS – British Computing Society
 Sets ethical standards that computing professionals
should adhere to.
 E.g. working beyond your capability
 Injuring others
 Taking bribes
 Privacy issues
 Social media.
 Journalistic invasion.
Computer systems
Environmental Considerations
 Energy
 Computers use energy
 Data centres use a lot.
 More energy than the aviation industry by 2014
 Inefficient generation of heat that has to be removed
 Air conditioning for machines
 Disposal
 E-waste
 Computers contain toxic and carcinogenic components
 Classified as hazardous waste
 Sent to landfill sites – toxic materials can escape into the
environment
 Sent to third world countries with poor environmental
policies. Danger to children and people trying to salvage
materials
Computer systems
Legal Constraints
 Data Protection Act 1998
 Computer Misuse Act 1990
Computer systems
Task
Answer questions on page 17. No writing is
required for the Extension question 4.