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# Lesson 1: scratch basics

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• Remember to hide the sprite from the screen
• ### Lesson 1: scratch basics

1. 1. Introduction to Programming Scratch Lesson 1
2. 2. Goals• What is an algorithm?• Scratch Interface• Variables• Conditional Statements• Turtle Graphics• Repetition 2
3. 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
4. 4. Scratch user interface 4
5. 5. Scratch stage 5
6. 6. Stage + Sprite• Exercise: – Point your mouse to coordinate x=0, y=0• Exercise: – Get a new sprite on the screen 6
7. 7. First scratch program 7
8. 8. Variables Add a variable called “number”Exercise:Say a random number 8
9. 9. ConditionsExercise: – What does this code do? – What are the errors in the code? 9
10. 10. ConditionsExercise: – What does this code do? – What are the errors in the code? – What if “number” is equal to 5? 10
11. 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. 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. 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. 14. Iteration • Repeat statements • Exercise: Guess what this code does • Test your guess 14
15. 15. Loop exercises• Exercise: Draw this (10 diamonds)• Exercise: Try to write your programs with as few statements as possible 15
16. 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