Year 7 · Spring 2

Scratch I: Programming essentials · Lesson 1 of 5

Algorithms vs programs: sequence with sprite movement

PracticalTopic 11 Algorithms

Year 7 · Scratch I: Programming essentials · Lesson 1 of 5

You will learn to

  • Explain the difference between an algorithm (the plan) and a program (the plan in code).
  • Write precise, ordered steps for a task, like making a jam sandwich.
  • Create a Scratch script that uses sequence: move, turn and say, in order.

Year 7 · Scratch I: Programming essentials · Lesson 1 of 5

Success criteria

You have got it when you can say:

  • I can say why 'put jam on the bread' is not precise enough.
  • I can make a sprite follow my steps in the right order.
  • I can predict what my script will do before I click the green flag.

Year 7 · Scratch I: Programming essentials · Lesson 1 of 5

Retrieval starter

Questions from before. Write your answers, then show them.

  1. Last unit

    =B2*C2 in D2 is filled down to D5. What is in D5?

    A =B2*C2B =E2*F2C =B5*C5

    C. =B5*C5

  2. Last unit

    Which field makes a good primary key?

    A HouseB FirstNameC StudentID

    C. StudentID

  3. Earlier this year

    Copyright in the UK…

    A Is automaticB Must be registered

    A. Is automatic

Year 7 · Scratch I: Programming essentials · Lesson 1 of 5

Key words (1 of 2)

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.

Year 7 · Scratch I: Programming essentials · Lesson 1 of 5

Key words (2 of 2)

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 · step 1 of 1 · part 1 of 2

What an algorithm is

A recipe or directions to a friend's house are algorithms. For a computer, an algorithm must be:

  • Precise: no step can be misunderstood.
  • Ordered: steps happen in a set order.
  • Finite: it must stop.
!Watch out

Computers are totally literal. 'Put jam on the bread' could mean putting the jar on the bread.

The explanation · step 1 of 1 · part 2 of 2

What an algorithm is (continued)

★Remember

An algorithm is the plan. A program is the plan written in a programming language.

Year 7 · Scratch I: Programming essentials · Lesson 1 of 5

Quick quiz · 1 of 3

Breaking a problem into smaller parts is…

  1. A Decomposition
  2. B Abstraction
  3. C Iteration

A. Decomposition

De-compose = take apart.

Year 7 · Scratch I: Programming essentials · Lesson 1 of 5

Quick quiz · 2 of 3

An 'if… else…' is…

  1. A Sequence
  2. B Iteration
  3. C Selection

C. Selection

It selects one path.

Year 7 · Scratch I: Programming essentials · Lesson 1 of 5

Quick quiz · 3 of 3

In a flowchart, a decision is a…

  1. A Oval
  2. B Diamond
  3. C Rectangle

B. Diamond

Diamonds have yes/no arrows coming out.

Year 7 · Scratch I: Programming essentials · Lesson 1 of 5

Exit ticket

Answer on paper before you go. Then check.

  1. The Tube map leaves out real distances. That's…

    A DecompositionB AbstractionC Pattern recognition

    B. Abstraction Abstraction removes detail that doesn't matter for the problem.

  2. How many times does FOR i ← 2 TO 8 repeat?

    A 6B 8C 7

    C. 7 Both ends count: 8 − 2 + 1 = 7 (2, 3, 4, 5, 6, 7, 8).