Chapter 9 | Computational Thinking

9.1 Computational Thinking

Computational thinking is a problem solving process where a number of steps are taken in order to reach a solution.

Abstraction

• Abstraction involves removing (filtering out) unnecessary data and keeping only necessary data.
• The solution is simplified so easier to implement
• The system is tailored to the need of the user
• An algorithm is an abstraction of a process that takes inputs, executes a sequence of steps, and produces outputs

Decomposition

• Decomposition means breaking down tasks into smaller parts to make it easier to solve. this is also known as stepwise refinement
• This can lead to structured programming using procedures and functions with parameters
• Can be represented using top-down diagrams:

9.2 Algorithms

• An algorithm is a solution to a problem expressed as a sequence of defined steps, and is done to perform a
• A good algorithm yields correct results, takes up very little memory, executes as fast as possible, and is concise, elegant, and easy to understand

Ways of representing algorithms

Structured english:
• A subset of the english language. consists of command statements
• Example structured english:
• Input a number
• Subtract 2 from the number
• Output the number

Pseudocode:
• Using keywords and identifiers to describe an algorithm. Resembles a programming language without following particular syntax; focuses on logic
• Example pseudocode:
  • INPUT Num
  • Num ← Num - 2
  • OUTPUT NUM

Flowchart:
• Consists of specific shapes linked together to represent sequential steps of an algorithm

Basic algorithm constructs:
• Assignment: An identifier is given a value or the value of a given identifier is changed
• Sequence: A number of steps are performed in order one after the other
• Selection: Choice of paths in a program (different steps are performed) depending on a condition. Selection is non-sequential
• Repetition: A sequence of steps is performed a repeated number of times. Also called iteration or looping