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Year 9 · Summer 2 · Raid: Capstone

Brief and planning: user needs, success criteria, task split

TheoryPresent ▶

What this lesson covers

Topic 14 Programming further

KS3 Computing · Real programs keep data in lists, take text apart as strings, split work into subroutines, check their input, save to files, and get tested on purpose.

Topic 11 Algorithms

KS3 Computing · An algorithm is a precise, step-by-step plan to solve a problem. Computational thinking turns a messy problem into one. Every algorithm is built from just three things: sequence, selection and iteration.

Computational ThinkingCambridge Lower Secondary Computing 0860

You will learn to

  • Identify the user and their needs from the brief the guild chose.
  • Write success criteria that a test can answer with a clear yes or no.
  • Use decomposition to split the project into parts, and give each part an owner.
  • Plan which parts are built in sprint 1 and which in sprint 2.

Success criteria

  • I can turn a vague goal, like 'easy to use', into a criterion I can test.
  • I can show our list of parts, with a name next to each one.
  • I can explain our plan to the teacher and get it signed off.

Key words

Say each word, then read what it means. Every one is in the glossary too.

List
One name holding many values in order. Also called an array.
Index
An item's position in a list, counting from 0.
Subroutine
A named block of code you can call when needed.
Function
A subroutine that returns a value.
Parameter
A placeholder in a subroutine for a value passed in.
Validation
Checking input is reasonable before using it.
Boundary data
Test data at the very edge of what's allowed.
Algorithm
Precise, ordered, finite steps to solve a problem.
Decomposition
Breaking a problem into smaller ones.
Abstraction
Ignoring detail that doesn't matter for the problem.
Sequence · selection · iteration
Steps one after another. First this, then this.
Pseudocode
Code-like writing for algorithms, without strict rules.
Trace table
Records variable values step by step to check logic.
Variable
A named place in memory that holds a value.

The explanation

Read it here, or open the study page below to go one step at a time with things to try.

The development cycle

Real software teams work in a cycle of five stages. This Raid follows the same cycle.

StageThe questionIn this Raid
AnalysisWhat is the problem, and who has it?Lesson 1
DesignHow will we solve it? Who does what?Lesson 1
BuildMake it, in small stepsLessons 2 and 3
TestDoes it meet every success criterion?Lesson 4
EvaluateWhat works, what does not, and what next?Lesson 5
★Remember

Success criteria are written now, before anyone builds. In lesson 4 you test against them.

User needs and success criteria

Choose one brief: a quiz app, a sensor device, a data story or a website.

Name the user. List what they need. A success criterion is one need, written so a test can answer yes or no.

e.g.Example

Guild brief: a binary quiz app to help Year 7 pupils revise. Users: Year 7 pupils who are new to binary.

Vague: you cannot test itTestable: yes or no
It is easy to useIt explains the rules in one short message at the start
It has lots of questionsIt asks 10 questions, one at a time
It checks the answersIt accepts only whole numbers from 0 to 255, and asks again if not
It keeps scoresIt saves the player's name and score to a file

Split the work

Use decomposition: break the project into parts. Give each part one owner.

PartOwnerSprint
Ask one question and check the answerAna1
Reject bad input and ask againLeo1
Choose 10 questions and keep the scoreSara1
Save the name and score to a fileOmar2
Join the parts and test them togetherEveryone2

Each part should work on its own. Then it can be tested on its own.

!Watch out

Show the criteria and the split to the teacher. Do not start building until the teacher signs them off.

e.g.Worked example

Turn the vague criterion 'The quiz is fair' into criteria you can test.

  1. Ask: what would 'fair' look like? You must be able to see it in a test.
  2. Every question has exactly one right answer. Test: check each answer by hand.
  3. An answer typed with spaces, like ' 5 ', still counts as 5. Test: type it and check it is marked right.
  4. The final score matches the number of right answers. Test: get 7 right on purpose. The quiz must say 7 out of 10.

Study it

Open the study page and go one step at a time.

Topic 14 · Year 9

Programming further

Real programs keep data in lists, take text apart as strings, split work into subroutines, and get tested on purpose.

Topic 11 · Year 7

Algorithms

An algorithm is a precise, step-by-step plan to solve a problem. Computational thinking turns a messy problem into one.

Check yourself

One question at a time. The reason shows after each answer.

Saved on this device.