Computer systems are based on processing data and
producing information and outputs. Computer systems are
electric which means they are fast and reliable. Most
importantly they are programmable which means they can be
made to perform different jobs; depending on the
instructions they are given.
All computer systems include:
Input devices Output
devices,Storage ,A
processor, Software
There are six main types of computer systems.
These are: • Dedicated systems • General
purpose systems • Embedded systems • Control
systems • Expert systems • Management
Information systems
Reliability of computer system
Avail
This is the percentage of
time the system is
available to the user or
customer but taking out
any planned downtime
perhaps for maintenance.
MTTF
Stands for “Mean Time To Failure”. This is the
average number of hours that the system
runs for before something breaks. This tends
to be a measure for hardware such as a
server. For example if a hard disk fails on
average 500 hours, then its MTTF figure is 500
hours.
Testing
Testing systems is a vital part of development and much time and effort
should be devoted to this. Computer systems can have thousands of lines of
code and limitless paths through it, for this reason reliability is hard to
achieve. Testing every aspect of a system is expensive and virtually
impossible. There will always be issues with systems so it is important that
systems are monitored through their lives. This is known as system
maintenance. System maintenance happens when changes are made to an
already installed system. Testing is not an attempt to show a system works.
Testing sets out to break the system to find where its weaknesses lie. When
a system is tested many elements of it may work but some may fail when
unexpected data is entered.
Most systems are released to a small group of users first so that the system can be tested under real
life conditions. This is known as beta testing.Alpha testing is first carried out in-house by developers
of the system. A system is tested against two key areas To identify weaknesses with the system in
meeting specification To identify errors when coding. Issues with the system design are harder to
fix than issues with coding.
Standards
Propietary standards
Industry standards
De facto standards
Open stadards
Environmental issues
Advantages • Helps find new ways to save the
environment • Is used everywhere • Improve
recycling • More people to work at home save
environment by not travelling to work • Don’t
need to print save trees • Used in solar panels
which is renewable • Uses less and less power as
they improve
Disadvantages • Uses electricity • Technological
waste • E-waste • Mining to make computers
• Expensive to produce • Damage environment
• Power/batteries