Computing Chapter 1 Fundamentals of computer systems (OCR)

Computer Systems

• A computer is an electronic, programmable data processing machine.
  
• A system is a collection of parts working together for a purpose, think about it like an organ system working together to keep you alive.
• A computer system is a collection of hardware and software that works together to achieve some data processing task 

Systems receive inputs from the outside. They process these inputs. They output the results of the processing.

This is an outline of a system:

Inputs - Processes - Outputs

A system is separated from the outside world by a system boundary.

These boundaries are often called interfaces.

Importance of Computer Systems

Most aspects of our lives are affected by computer systems.

They have led to:

• Improved quality in manufacturing - robotic machinery is more accurate
• Cheaper manufacturing - don't have to pay the machines wages and allows 24/7 working
  
• Faster to access information - jobs can be done quicker with computer systems to help
• Better decision making - with lots of organised, available facts decision can be better informed
  
• New ways of doing business - more buying online, more choice
• New ways of communicating - email, SMS, mobile phones

Example of a computer system you may have used:

Washing machine, Inputs: temperature, water levels, dirtiness, Outputs: timer Processing: check values, determine washing parameters

General Purpose Systems

• Personal computers such as desktops, laptops, and smartphones
• They're designed to perform multiple tasks
• Various applications (apps) can be loaded so they can be used for different purposes

Dedicated Systems

• Specially produced to perform a single function or set of functions
• For example, a ticket machine at a train station it performs a single set of instructions 

Embedded Systems

• Computer systems that are part of a larger system
• Can be simple and can be complex
• They include some portable devices such as digital watches, satnavs, cameras

Expert Systems

• Computers designed to behave like a human expert
• They have a knowledge base, an inference engine, and an interface
• They are commonly used for diagnosing diseases, finding faults in machinery

Computer might have a role in life or death situations:

• Aircraft navigation and control
• Railway signalling
• Many medical situations 

Medical computers have important activities:

• Record keeping
• Diagnosis of diseases
• Drug interactions 

Mistakes in the design and production of systems can lead to:

• Down time 
• Expensive errors
• Data loss
• Compromised privacy

Data Integrity

• This relates to data being accurate and consistent throughout its life
• Also means that the data store reflects real-world reality
• Database systems usually have rules that prevent inconsistent changes being made

Data Integrity can be Compromised by:

• Human errors when data is entered 
• Errors that occur when data is transmitted
  
• Software bugs
• Hardware malfunctions

Ways to reduce risks:

• Backing up data regularly 
• Controlling access to data 
• Using validation rules

Reliability and Testing 

Reliability is improved by thorough testing. Testing is designed to uncover errors.

Testing can never be complete:

• Software is so complex
• Testing is expensive
• Testing is time-consuming

There are huge numbers of pathways through most modern systems so there are usually errors even in extensively tested systems. 

There are various categories of standards

In computing, standards exist for:

• Programming languages
• Operating systems
• Data formats 
• Communication protocols 
• Electrical interfaces

Originally there were no standards. This was a problem. 

Standards are important because they:

• Enable equipment from different manufacturers to work together
• Make learning new systems easier because they have similar characteristics 
• Minimise waste
• Brings costs down by opening markets to competition

De facto standards

Standards developed over time from common use.

They make it so files and systems can be used by anyone

Examples:

• Postscript 
• The QWERTY keyboard
• Microsoft Word

Proprietary Standards

• They are owned by an organisation.
• The ensure compatibility between the companies products
• They are widely used but not approved by an independent standards body 
• Because products have the similar interfaces it makes learning and getting to grips with the product easier.

Open Standards

• publicly available
• produced collaboratively 
• not dominated by any one interest group
• not for a profit and available free of charge or at a small cost
• sufficiently detailed 

Open standards ensure that access to resources is not dependent upon:

• a single application 
• a particular hardware platform 

Some examples of open standards:

• SQL
• HTTP
• HTML
• WAP

An ethical act is one that is morally right, and a legal act is one that doesn't break any laws.

Computers have laws about:

• privacy 
• data security
• access to sensitive data
• copyright

Data Protection 

The data protection act covers any data about a living and identifiable individual.

Typical data protection laws include provisions that organisations must:

• allow people to view data held about them 
• correct information when requested 
• only collect data for a specified and lawful purpose 
• not use data in any way that may potentially cause damage or distress

Waste 

Old computers which are no longer in use have to be disposed of. They contain toxic materials such as:

• lead
• cadmium 
• beryllium 
• flame retardants

E-waste is often shipped to developing countries where there are few safeguards. Much waste goes to landfills, where toxic chemicals can leak into the soil. Old computers contain a lot of plastics, for example in circut boards. When these are burnt they release dangerous chemicals such as dioxins.