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Year 7 · Summer 1 · Scratch II: Subroutines and lists

Lists: high scores and inventories

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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.

ProgrammingCambridge Lower Secondary Computing 0860

You will learn to

  • Explain what a list is and why it is better than lots of separate variables.
  • Use blocks to add an item, delete an item and show one item from a list.
  • Explain that Scratch counts list items from 1, but Python counts from 0.

Success criteria

  • I can make a list of names and a list of scores.
  • I can add an item, delete an item and show item 1.
  • I can say that the first item is item 1 in Scratch and index 0 in Python.

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.

The explanation

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

Lists

A list (or array) stores many values under one name, in order.

scores = [12, 45, 33, 50]
Index0123
Value12453350
?Why?

Why start at 0? The index means 'how many steps from the start'. The first item is 0 steps away.

  • scores[0] → 12
  • scores[-1] → 50 (the last one)
  • scores.append(28) adds to the end
  • len(scores) → how many items
  • scores[10] → error: no item there

Study it

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

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.

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.

Check yourself

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

Saved on this device.