2.1.1 Thinking Abstractly

Question 1

Representational Abstraction

Answer 1

• Removing excessive details to represent a problem using only the key features
• Must analyse what is relevant to a scenario and simplify a problem based on this

Question 2

Data Abstraction

Answer 2

• Details about how data is being stored are hidden
• Programmers can use data structures without knowing how they are implemented

Question 3

Layers of Abstraction

Answer 3

• Large, complex problems are split into layers of abstraction
• Each layer has a different role, with the highest layers being closest to the user
• These are usually responsible for providing a user interface
• The lowest levels perform tasks such as interacting with machine components

Question 4

Abstraction By Generaisation

Answer 4

• Grouping together similarities within a problem to identify what kind of problem it is
• Allows problems to be categorised as being of a particular type
• A common solution can be used to solve these problems

Question 5

Procedural Abstraction

Answer 5

• Allows programmers to utilise functions without knowing how they are implemented
• Used in decomposition and manipulating data structures
• Models what a subroutine does without considering how, as once a subroutine has been written, it can be reused as a black-box

Question 6

The need for abstraction

Answer 6

Abstraction allows non-experts to use of a range of systems or models by hiding information that is too complex or irrelevant to the system’s purpose

Enables for efficient software design as programmers can focus on core elements rather than unnecessary details

• Reduces the time spent on a project
• Prevents a program from getting unnecessarily large

Programming languages use layers of abstraction:

• Low-level languages directly interact with computers but are difficult to write
• High-level languages abstract the machine code that is executed when a program is run by providing easy-to-use syntax similar to natural language
• Makes developing programs easier
• High-level languages are easier to learn and use than assembly language or machine code
• Makes coding accessible to non-specialists

Question 7

Abstraction vs Reality

Answer 7

• Abstraction is a simplified representation of reality
• Entities are represented as computational structures eg. tables and databases
• Real-world values can be stored as variables and constants
• Objects in object-oriented programming are an abstraction for real-world entities
• Attributes represent the characteristics of an object
• Methods represent the actions a real-world object is able to perform

Question 8

Devise an abstract model for a variety of situations

Answer 8

When devising an abstract model given a scenario, you must consider:

• What is the problem that needs to be solved by the model?
• How will the model be used?
• Who will the model be used by?
• Which parts of the problem are relevant based on the target audience and purpose of the model?

Question 9

Benefits of abstraction when writing a program

Answer 9

• Reduces programming time
• Reduces complexity of code (through abstraction by generalisation)
• Reduces amount of memory required / computational power
• Simplifies the problem so it’s easier to solve / understand (by recognising common patterns)
• Allows programmers to focus on core aspects of the problem