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 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.