2. 1. 1 Thinking Abstractly

Question 1

The nature of abstraction

Answer 1

• It is the process of removing excessive details to come to a representation of a problem that consists of only the key features
• Icons is a great example of abstraction, suggest a function or process in a simple and efficient way

Question 2

Representational Abstraction

Answer 2

• Analysing what is relevant to a given scenario and simplifying a problem based on this info

Question 3

Abstraction by generalisation

Answer 3

• This involves grouping together similarities within a problem to identify the type of problem being dealt with
• Allows categorisation of problem being of a particular type so that a common solution can be used to solve these problems

Question 4

Data and Procedural abstraction

Answer 4

• A subcategory of abstraction, details about how data is being stored is hidden
• Programmers can use abstract data structures (stacks, queues) without concerning themselves with how the structures are implemented
• Programmers can also perform functions (pushing, popping etc) in a stack without having knowledge of the code used for this functionality, known as procedural abstraction also used in decomposition
• Models what subroutine does without considering how this is done
• Once procedure coded, can be reused as a black-box

Question 5

Abstraction in large complex problems

Answer 5

• Larger more complex problems use multiple levels of abstraction, each level performs different role
• Highest levels of abstraction are closest to user, usually responsible for providing interface for user to interact with hardware
• Lowest levels responsible for performing these tasks through execution of machine code

Question 6

The need for abstraction

Answer 6

• Allows non-experts to make use of range of systems or models by hiding info that is too complex or irrelevant to the systems purpose
• For example, a gamer does not need to know how the game has been coded
• Enables more efficient design during software development, programmers can focus on elements that need to be built in software rather than unnecessary details being a concern
• Reduces time needed to on the project, prevents program from getting unnecessarily large by removing wasteful details early

Question 7

Abstraction in programming languages

Answer 7

• PL can be separated into spectrum of high-level and low-level languages
• Low-level like assembly code and machine code directly interact with computer systems, more difficult to write
• Requires an understanding off binary codes and memorisation of mnemonics
• High-level provides abstraction for machine code, makes development easier, syntax parallels natural language in high-level, considerably easier to learn compared to low-level
• This makes coding accessible to non-specialists

Question 8

Abstraction in networking

Answer 8

• TCP/IP model is an abstraction for how networks function, separated into four layers
• Each layer deals with different part off communication process, separating them makes them simpler to understand
• Does not need to know what is happening on other layers
• Important to ensure compatibility between layers so standards must be agreed on in advance
• The model uses a set of protocols is that each layer can be dealt with individually, details about other layers hidden
• Basically, abstraction gives us a more simplified understanding of how the model works

Question 9

Difference between abstraction and reality

Answer 9

• Abstraction is a simplified representation of reality; real-world entities can be represented using computational structures such as tables and databases
• Real-world values often stored as variables; OOP uses objects which is an abstraction for real-world entities
• Basically, abstraction acts as a representation through OOP and some data structures

Question 10

Things to consider when devising an abstract model

Answer 10

• What is the problem that needs to be solved?
• What are the key features of the problem?
• Can it be solved computationally?
• How will the model be used?
• What sort of format does the model need to be displayed in?
• Consider factors such as convenience, affordability and ease of access
• Who will the model be used by?
• How many people will be using the model?
• What level of expertise do they have in the subject/ discipline associated with the problem?
• Which parts of the problem are relevant based on the target audience and the purpose of the model?
• Remove sections that are not relevant to the problem that needs solving
• Remove details that will confuse the audience