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Processing - batch, on-line & real-time processing
Here are some examples of past exam questions:
June 03 P2.6
1) Give two situations where real-time processing is used. 
Two answers from:
System to monitor hospital patients e.g. to check heart is beating
Greenhouse control system.
Automatic pilot/Aircraft onboard flight control system/fly by wire system.
Defence system/guided missiles/guided weapons
Nuclear power station.
Intruder alarms/burglar alarms
Air traffic control
Computerised level crossing
Computerised central heating system/computer controlled central heating system
Distance sensing systems in vehicles
Chemical processing plants
Any other answers where an immediate response is essential.
June 04 P2.12
2) An airline uses batch, on-line and real-time data processing.
a) Which type of data processing would be most appropriate for:
i) Reservations - on-line processing
ii) Payroll - batch processing
iii) Automatic pilot - real time processing
b) Choose one of these data processing methods and explain how it works. 
On-line processing - Once passenger decides to book seats an (interactive) link is established  between travel
agent's computer and airline's reservation records for that flight, a write restriction is applied to database records
for that flights seating. . When booking is complete and/or link is between the computers is broken then the write
restriction is removed.  This prevents double booking. 
Batch processing - Data about how many hours people have worked etc is collected together before being entered
into the computer . The computer then processes/calculates the `batch' (the wages) in one single operation .
This process takes advantage of the computer's ability to perform very high speed processing providing the data to
be processed is input at a similar speed . Once the processing is started very little human intervention is needed.
Real-time processing - Sensors feed information about a lot of conditions regarding the plane to the on-board
computer  (e.g. how close it is to another plane). On board computer calculates appropriate response  (e.g.
does it need to go higher or lower) and immediately feeds back appropriate controlling information  (tells plane
to go higher or lower) to ensure all sensor inputs remain within allowable limits  (so that doesn't get too close to
June 05 P2.2
3) A company uses batch processing to produce wage slips for its employees. Give two reasons why `real-time
processing' is not used for this task. 
Two answers from:
Real-time processing would do the wages as soon as the data about what to pay the workers was entered but
there is no need for the processing to be immediate as the wages are only done once a week or once a month.
The system will not need to accept continuous input - data about what to pay workers only needs entering every so
often not continuously.
No need to continuously update someone's wages but with real time processing there needs to be continuous
Real-time processing would mean there was constant use of processing power which would be a waste as it isn't
The processing cannot start until all the data for the week or month has been collected so the processing cannot be
continuous (real-time processing is continuous). Batch processing will just process the data once all the needed
data has been input e.g. it will work out the wages once a week or once a month.
June 06 P2.2
4) Explain why an aeroplane flying on autopilot uses real-time processing rather than batch processing. 
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Here's a taster:
An instant response is required as the autopilot means a computer is flying the plane. If the computer used batch
processing then it would receive several instructions which it would store before it followed them & this could lead
to the plane crashing. The computer needs to respond to instructions as soon as it receives them which is what
real-time processing does e.g.…read more