Follow & Write Algorithms (Edexcel GCSE Computer Science)

What is an algorithm?

• An algorithm is precise set of rules or instructions to solve a specific problem or task

• There are two main ways to write an algorithm

  • Flowchart

  • Pseudocode

Flowcharts

What is a flowchart?

• Flowcharts are a visual tool that uses shapes to represent different functions to describe an algorithm

• Flowcharts show the data that is input and output, the processes that take place and any decisions or repetition

• Lines are used to show the flow of control

Example

Flowchart

• The casino would like the algorithm refined so that the user also enters their first name and this is used to greet the user when they access the site

Flowchart

Pseudocode

What is pseudocode?

• Pseudocode is a text-based tool that uses short English words/statements to describe an algorithm

• Pseudocode is more structured than writing sentences in English but is very flexible

• In exams, pseudocode will appear in the format of Python 3 as per the Programming Language Subset (PLS) document from Edexcel

Example

• A casino would like a program that asks users to enter an age, if they are 18 or over they can enter the site, if not then they are given a suitable message

• The casino would like the algorithm refined so that the user also enter their first name and this is used to greet the user when they access the site

• Practical use of Pseudocode is covered in section 6 here