Algorithms, Decomposition & Abstraction (AQA GCSE Computer Science)

• Solving problems that can be implemented by a computer system is known as computational thinking

• There are three main principles of computational thinking:

  • Algorithmic thinking

  • Decomposition

  • Abstraction

Algorithms

What are algorithms?

• Algorithms are a set of step-by-step instructions in order to produce a solution to a problem

• Algorithmic thinking requires the use of abstraction and decomposition to identify each step

• Once each step has been identified, a precise set of rules (algorithm) can be created and the problem will be solved

• An example of algorithmic thinking is following a recipe, if the recipe is followed precisely it should lead to the desired outcome

• A set of traffic lights is an example of how algorithmic thinking can lead to solutions being automated

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

• An examples of decomposition in computing is:

Computer games

• Modern computer games are decomposed 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

Abstraction

What is abstraction?

• Abstraction is the process of removing unnecessary details from a problem to focus on the important features for implementing a solution

• Examples of abstraction include modelling a real-life object, environment, action, sequence of actions or concept.

• Implementations of these include:

  • a computer game that simulates playing a sport

  • a simulator such as a car or flight simulator,

  • a map of a bus or train route in a city

• When creating a program, developers must identify important features that will contribute to solving the problem or have a role to play in the solution

Computer games

• Computer games use a large amount of abstraction, removing the elements that a user does not need to consider in order to enjoy playing the game

• When using abstraction in computer games which are designed to simulate real life, the aim is to make the game realistic and visually appealing whilst keeping the game fun to play

• In a game that simulates a sport, it is important to the user that visually they recognise the environment and when they perform an action, they see a response

• However, users do not need to know the complex algorithms used to control the non player characters (NPCs)

Train map

• Another specific example of abstraction would be the London underground train route map; travellers do not need to know the geographical layout of the routes, only that getting on at stop A will eventually transport you to stop B