Structure diagrams

2.1.2 Designing, creating and refining algorithms

Designing, creating and refining algorithms — Note 2 of 7

Produce simple diagrams to show:The structure of a problem, Subsections and their links to other subsections

What you need to know

Structure diagrams are visual representations that show how a problem can be broken down into smaller sub-problems. They use a tree-like hierarchy where the main problem is at the top and each level below breaks it into smaller tasks. This is a direct application of decomposition and helps plan the design of a program before writing code.

What to know

Structure diagrams show the hierarchy of a problem broken into sub-problems.
The main problem sits at the top, with sub-problems branching below it.
Each sub-problem can be further broken down into even smaller tasks.
They help visualise how different parts of a program relate to each other.
Structure diagrams are useful for planning before writing pseudocode or program code.
They are a direct application of the decomposition principle of computational thinking.
Scenario
A secondary school wants a parents' evening app so that parents can arrange meetings with their child's teachers. To use the app, a parent must first log in by entering their username and their password. Once logged in, the parent can book an appointment. To do this, they choose the teacher they want to see and then choose an available time slot. Parents can also view the appointments they have booked. They can choose to see their appointments on-screen, or print them out to bring with them on the evening. Draw a structure diagram to show how the parents' evening app can be decomposed into smaller sub-problems.
Whole problem: The opening sentence names the app, which becomes the top box.
Three sub-problems: The three things a parent can do ("log in", "book an appointment", "view the appointments") are the middle level.
Smaller tasks: The details within each of those sentences (username and password; teacher and time slot; on-screen and print) are the bottom level.

Exam technique

Tip:You may be asked to complete a structure diagram by placing tasks into boxes. Read the scenario carefully to identify which tasks belong at each level.

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