Lesson 1: scratch basics
- 1. Introduction to Programming Scratch Lesson 1
- 2. Goals • What is an algorithm? • Scratch Interface • Variables • Conditional Statements • Turtle Graphics • Repetition 2
- 3. What is an algorithm? • A step by step process (Algorithm) – Instructions for making tea (Pseudocode) If no water in kettle: Put water in kettle Turn on kettle While water not boiling in kettle: Wait Put water in cup … 3
- 5. Scratch stage 5
- 6. Stage + Sprite • Exercise: – Point your mouse to coordinate x=0, y=0 • Exercise: – Get a new sprite on the screen 6
- 8. Variables Add a variable called “number” Exercise: Say a random number 8
- 9. Conditions Exercise: – What does this code do? – What are the errors in the code? 9
- 10. Conditions Exercise: – What does this code do? – What are the errors in the code? – What if “number” is equal to 5? 10
- 11. Motion statements • Move Right • Move Left • Big Steps • Small Steps • Move Up • Move Down • Exercise: Double-click on the blocks to see what happens 11
- 12. More motion action • Exercise – Make the sprite go to x=0, y=0 • Exercise – Make the sprite move 100 steps and turn 90 degrees • Exercise – Make the sprite go in a square pattern • Exercise – Make the sprite move when you hit a key 12
- 13. Pen statements • Pen appears underneath sprite • Pen must be set to “down” before it will draw • Exercise: Draw a line after the sprite 13
- 14. Iteration • Repeat statements • Exercise: Guess what this code does • Test your guess 14
- 15. Loop exercises • Exercise: Draw this (10 diamonds) • Exercise: Try to write your programs with as few statements as possible 15
- 16. More repeating exercises • Exercise: Draw this in any colour • Exercise: Change the colour of each square • Exercise: Draw a triangle, a pentagon a hexagon and a circle. 16