Problem Decomposition (Cambridge (CIE) O Level Computer Science): Revision Note

Problem Decomposition

What is decomposition?

• Decomposition is the process of breaking down a large problem into a set of smaller problems

• Benefits of decomposition are:

  • Smaller problems are easier to solve

  • Each smaller problem can be solved independently of the others

  • Smaller problems can be tested independently

  • Smaller problems can be combined to produce a solution to the full problem

• Modern computer games are a good example of using decomposition to break down the complexity of the problem into more manageable 'chunks'

• Creating an entire game at once would be challenging and inefficient, so it could be decomposed into:

  • Levels - Levels can be designed/created/tested/ independently of other levels

  • Characters - The mechanics of characters in the game can be designed and created by a separate team

  • Landscape - The art team can work on the visual aspects of the game without needing to understand how the game is programmed

• Once all of the smaller problems are completed, joined together a complex game has been created

Inputs, processes, outputs and storage

• Decomposing a problem requires developers to think about four component parts:

  • Inputs: data entered into the system

  • Processes: subroutines and algorithms that turn inputs and stored data into outputs

  • Outputs: data that is produced by the system, such as information on a screen or printed information

  • Storage: data that is stored on a physical device, such as on a hard drive or in memory whilst the program is running

Example - Area of a rectangle program