FUNDAMENTALS OF COMPUTER SYSTEMS Lesson 1

Starter What is the difference between hardware and software?

Feedback Hardware = the physical components of a computer system; anything that can be seen or touched, e.g. monitor, hard disk, keyboard Software = the programmes that run on the hardware, e.g. the operating system, Word, Scandisk

Objectives from the specification 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.

Define a Computer System? What goes where? Storage, input, process, output

What is a computer system? A computer system is a collection of parts that receives and processes inputs in order to produce outputs.

What is an embedded system? A computer system that forms part of an electronic device

How many devices can you think of with embedded computer systems? Washing machines Cameras Burglar alarms Telephones Fridges Microwaves Television Games console Engine management system GPS Stereo

6 mark question – June 2013

Answers

Why is it important that computer systems are reliable? What would happen if your xbox stopped working? What would happen if the school network went down? What would happen if motorway signage failed? What would happen if a life system monitor stopped working? What would happen if a fly-by-wire system stopped working? SOMETIMES RELIABILITY IS MORE IMPORTANT THAN SPEED

How do you measure reliability in a computer system? The main measure is system availability, e.g. if a system is down for 1 hour in a hundred then the system availability is 99%. Another way of measuring reliability is to measure the length of time between system failures. The Mean Time Between Failures (MTBF) is often quoted by equipment manufacturers as a an indication of reliability.

How do companies protect against system failure? Hardware redundancy is when there is more than one of a critical component, so that if one fails then another one can be used Backups are when a copy of the data is saved and stored away from the original data. You can only recover data up to the last time it was saved Disaster recovery plans are when a company has in place a plan that allows them to switch over to a completely new set of hardware in a very short space of time Rigorous testing means that the computer system is tested to try and avoid unexpected data or situations that could cause the system to fail Agreed standards are ways of working that mean that code and hardware are made to be compatible with each other

6 mark question – Jan 13

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Standards Computer systems, both hardware and software are developed by professional engineers. Professional engineers are trained to use the appropriate standards. Standards capture 'best-practice'. So the learning gained from earlier projects are carried through to new ones. Developing a non-trivial system usually involves many people. This needs discipline, project planning and standards. There are standards and techniques available to help with the development phase. There are standards in place to help with change control and maintenance.

Professional standards in system development There are several approaches to system development Two of the most common are the Waterfall method and Rapid Application Design These are both standard approaches that teams of developers would be familiar with. They wouldn’t have to learn a new methodology every time they move to another job.

Professional standards in documentation The symbols used in flow charts are industry standard, so are the symbols for logic gates These standards mean that system developers can: Work in teams because they all have a common understanding of the design diagrams Move between companies because the same design tools will be used in all Pick up someone else’s design and code it Maintain someone else’s design

Professional standards in coding These include: commenting what you have created to explain what it does Indenting to show sections of code and make it easier to read Using meaningful identifiers (e.g. variables and function names) so that anyone can read the code and understand it

Standards Proprietary standards These are owned by a company and covered by copyright law Industry standards These are agreed across the whole computing industry De facto standards These are standards that have developed through “common usage” Open standards These are standards that are publically available

6 Mark question – June 2012

Answers

Legal considerations When a computer system is designed and implemented it must meet legal requirements. For example: The Data Protection Act The Health and Safety at Work Act (including Display Screen Regulations) The Copyright, Designs and Patents Act

Ethical considerations These are all about fairness and what is right and wrong. Examples of ethical issues include: Should companies use local programmers and call centres? Are countries like India being exploited as a source of cheap labour for call centres and for programming? Does the system design promote accessibility for all?

Environmental considerations Environmental issues include the carbon footprint and waste products that result from manufacturing computer systems but this is often outweighed by the positive effects on the environment of using computerised systems to manage processes that might otherwise generate more pollution. Considerations might include: Does a computer system mean that people can work from home and therefore drive less? Does a computer system mean more manufacturing? Do computer managed engines work more efficiently and create less pollution and use less fuel?