Computing - Fundamentals of Computer Systems

• Computer - Electronic, programmable data processing machine
• System - Collection of parts that wrok together for some defined purpose
• Computer System - A collection of hardware and software that works together to achieve some data processing task
• Systems recieve inputs from the outside. They process these inputs. They output the results of the processing
• A system is seperated from the outside world by a system boundary (Interfaces)

Most aspects of our lives are affected by computer systems:

• Improved quality in manufacturing 
• Cheaper manufacturing
• Faster access to information
• Better decision making 
• New ways of doing business e.g. Online shopping 
• New ways of communicating e.g. SMS 

Holiday Booking

• Input: Dates, destinations, credit card details
• Outputs: itineraries, air tickets, hotel reservations
• Processing: Check availability, produce documents

Satnav

• Input: Signals from satellites, Input from user
• Output: Route, places of interest, warnings
• Processing: check position, locate on map, output map

• General Purpose - Designed to person multiple and can contain various applications e.g. smart phones and laptops
• Dedicated systems - Specially produced to perform a single function or set of functions e.g. a ticket vending machine 
• Control systems - Computer systems that control machinery, rather than produce output for humans to reat or respond to
• Embedded Systems  - Computer systems that are part of a large systems and they are usually also control systems e.g. Car systems
• Expert Systems - Computer systems designed to behave like human experts (Contain knowledge base, inference engine, an interface) e.g. used for making credit checks and diagnosing diseases 
• Management information systems - Bring together the information from all parts of an organisation so that mangers can make sensible decisions e.g. Office automation systems automate workflow 

• Computers can play a central part in many life or death situations e.g. aircraft navigation and control 
• Medical computer systems innclude activities such as record keeping, diagnosing diseases and DNA sequencing 
• Reliability is expected when new computer systems are made - Mistakes can lead to: down time, expensive errors, data loss and compromosed privacy

• Integrity - Relates to data being accurate and consistent and makes sure that stored data reflects real world reality
• Database systems have rules that prevent inconsistent changes being made to data
• Data integrity can be compromised by: human errors, software bugs, hardware malfunctions and natural disasters
• Risks to data can be reduced by: Backing up data regularly, controlling access to data via security and using error detection and correction software 

• Reliability is improved through testing
• Testing is designed to uncover errors 
• Testing can never be complete because: software is complex, testing is expensive and time consuming 
• There are a large number of pathways in modern systems - there will always be errors 

• Standards - Conventions and rules for programming languages, operating systems, data formats, communications protocol etc.
• Originally there were no standards and each computer manufacturer made up its own rules
• Standards are important because they: enable equipment from different manufacturers to work together, make learning new systems easier, minimise waste, ensure fair play access to markets 

• De facto standards - Develop over time because of common usage - ensure that files and systems can be used by anyone
• E.g QWERTY keyboard layout, Microsoft word

• De Jure Standards - De facto standards that have become so universally accepted that they have to be adhered to by law
• Examples: ASCII, Unicode

• Owned by an organsation and ensure compatibility between the company's products 
• Often wifely used but are not approved by an independant standards body e.g. Windows 

• Industry Standards - Set by recognised non-commercial organisations e.g. Americal National Standards Institute 

• Publicly available
• Produced collaboratively
• Not dominated by any one interest group
• Not for profit and available for free
• Sufficiently detailed 
• Examples: HTTP, HTML, XML

• Ethical act - One that is morally right
• Legal act - one that does not break any laws 
• Widespread computer use has produced new legal and ethical challenges regarding: privacy, data security, access to sensitive data and copyright

• Most governments have enacted laws that are intended to protect the privacy of individuals e.g. UK Data Protection Act
• Legislation is needed because it is easy to copy data, transmit data and match data and make judgements about people
• Other Laws such as copyright designs and patents act & computer misuse act

Principles of Data Protection Laws, Organisations must:

• Allow people to view data about them
• Correct information is requested
• Not use data in any way that may cause damage or distress
• Allow people to state that their data is not to be sold
• Protect data from unauthorised access
• Only collect data for specified purpose
• Not transmit personal data outside the European Economic area

Nowadays, a lot of cyber crime (crimes comitted with the aid of computers) are comitted & these criminals are difficult to find

• Computers can benefit and damage environment e.g. Reduces need for travel and transport of goods, can lead to more efficient products that last longer and use energy more efficient
• Unused computer have to be disposed of - Contain toxic materials e.g. lead and cadmium
• E-waste is often shipped to LEDCs and put in landfills (where toxic chemicals can leak into soil & release dangerous toxins when burned)

Computer use a lot of energy and so do data centres. Methods to reduce energy used by computers include:

• Virtual servers rather than physical ones
• Solid state storage uses less energy
• Automatic standby switching 
• Laying out equipment so that it can be cooled efficiently