Introduction to information systems T. Cornford, M. Shaikh is1 060 2013

closed systems
that 
have no interaction beyond themselves or 
open systems
that interact 
with and change their environment (beyond their own boundary). Figure 
3.1 schematically shows a system made up of interacting components and 
taking inputs from its environment and providing output to it. The system 
is controlled by some feedback process that ensures that as far as possible 
the desired output is produced. 
Activity
Consider an air-conditioning system. Its main components are a compressor unit, a fan, 
ducting and a thermostat that senses the temperature and controls the compressor – 
turning it on or off. Explain this system in terms of it being an open or closed system, the 

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Chapter 3: Core concepts: information, data and systems
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inputs and outputs involved and the control process or feedback that steers the system. 
What would you see as the ‘purpose’ of the system…what does it strive to achieve? How 
does the output of the system change the environment and thus the input?
Input
Output
Feedback
System boundary
System enironment
Figure 3.1: Systems environment.
Activity
Would you consider the economic system of your country as an open system or a closed 
system?
Taking the online book store Amazon as a system embedded in an environment of 
potential purchasers, explain with an example how the control or feedback might work. 
First consider what the inputs and outputs are and what the purpose of the system is. 
Then try to show how information on outputs can ensure more or better inputs. (Hint: If 
outputs are books shipped to people, how can we use that data to improve the number 
of inputs (for example, orders)?
Information systems are by definition examples of open systems – 
although specifying the boundary (what is in and what is outside) 
can be tricky. Thus, information systems have some relations with the 
environment beyond their boundary – accepting inputs and generating 
outputs. For example, a payroll system for a company will:
• take in data about who worked how many days as inputs
• process this data in various ways to calculate how much to pay people 
and how much income tax to deduct 
• generate instructions to a bank to transfer money to the workers’ bank 
accounts as outputs, and tax to the government. 
This process all has some effect on the company’s environment. If people 
are paid on time and correctly there is one effect; if they are paid late or 
too little, there is another!
The principal interactions between an information system and its 
environment can be described as the:
• receipt of signs or signals from the environment as