A simulation is the creation of a model of real system in order to study the behavior of the system .
The model is generated and is based on mathematical representations .
And this is used to find out mechanisms control how a system in the future and also see the possibility to influence this future behavior.
Computer modelling have advantage like:
• Saving money
• Get information & solution more quickly .
• And more secure
And modelling application have many example :
• Traffic light simulation
• A model showing profit/loss
1. Tuck shop
This is the example uses a spreadsheet to do modelling.
And this is used to show a model of profit /loss from our selling.
2. Traffic light simulation
Used to demonstrate complex simulation , like traffic light
• Data collection
The success or the failure of a simulation model depends on how realistic it is ,
Data needs to be collected by watching traffic for a long period of time at the junction ( a traffic light in each road). This is the best done by using induction loop sensors which count the number of vehicle at each junction, manual data collection is possible but is prone to error and its difficult to do over 18 hours period , for example the following data should be collected:
• The number of vehicles passing junction in each area
• The time of day for vehicle count
• How many vehicles build up at the junction at different time a day
• How vehicle movement change at weekends
• How long it takes the slower & the fast vehicle
• The movement made by the vehicles ( example: turn left or right , filtering, etc)
• Environmental factor, like pedestrian crossing nearby.
Using the simulation
This simulation is used to optimize the flow of traffic through the junction on an ongoing basis.
• Sensor in the road gather data & count the number of vehicles at junction.
• This data is sent to a control box or a computer.it may need to be converted first into form understood by the computer.
• The gathered data is compared to data stored in the system. The stored data is based on model / simulation predictions. Which used to optimize the traffic flow.
• The control box or computer decides what action needs to be taken .
• Signals are sent out to the traffic light to change their timing necessary .
Advantage of using the simulation
• Less expensive
• Safer to run a simulation
• Various scenarios can be tried out in advance
• Nearly impossible to try out some task in real life because of high risk involve (example : in outer space , under the sea , in nuclear reactors, crash test ,etc.).
• Faster to do simulation than the real thing . this is most used in population growth, climate change , etc.
Disadvantage
• Only as good as the data used and the mathematical algorithms representing the real life situations. limited in use in some very complex application example : simulating a nuclear process.
• Can be very expensive to set up and require a specialist.
• Require a processors/ computer system s, to do necessary
Type of processing
3 basic of processing:
• Batch processing
• Real rime (transaction) or online processing
• Real time process control .
1. Batch processing
Sometimes we have a lot of data to process and it is all of a similar form (e.g. we might have to calculate the pay for 10,000 employees – the calculations we have to do for each employee are very similar)
In cases like this, we can prepare the data into a set or ‘batch’ and hand it over to the computer to be processed in one go. Once we have prepared the batch of data, no user input is required – the computer works its way through the data automatically.
This type of data processing is known as batch processing.
An advantage of this type of system is that the processing can occur when the computer is not being used for anything else (e.g. at night). The job is setup, people go home, and when they return the next morning the work has been done.
Typical application where batch-processing can be used:
• Payroll processing 
• Processing bank cheques
• Printing of bank statements
• Updating of a stock database
2. Real time processing
Sometime we need to process data immediately – we cannot wait and process it later (e.g. using batch processing)
For example, if we want to book a seat on a flight, the booking must be processed immediately. We can’t put it in a pile and do it later, because other people might be trying to book the same seat!
If an item of input data must be processed immediately, and the result is ready before the next input data is accepted, this is known as a real-time system.Typical application where real-time processing must be used:
Any type of monitoring system (e.g. hospital patient monitoring)
Any type of computer control system (e.g an automatic production line, an aircraft auto-pilot, the system controlling a nuclear power station, etc.)
Payment systems (e.g. EFPOS and ATM cash withdrawal)
All booking systems (e.g. flight booking, cinema seat booking, etc.)
Computer games (e.g. FPS, driving games, etc.)
3. Online process
An on-line system is one where the user is directly interacting with the computer – the user is ‘on-line’ with the computer.
So, any system where the user is entering data directly into the computer must be an on-line system. If data is being entered and then processed, it’s an on-line processing system.
Examples of on-line processing systems:
All booking systems (e.g. flight booking, cinema seat booking, etc.)
More and more businesses and organisations are storing our personal data so that it can be used to contact us later, for purposes like marketing (selling us things). Every time you fill in a form on a website, or sign up for a special offer, your details are stored in a database somewhere.
If the data in a database falls into the wrong hands, this can lead to some very big problems.
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