1.2 Scr0320: memory, variables, and literals in scratch 2.0

Table of contents

• Preface
  • Student programming projects
  • Viewing tip
    • Images
• General background information
  • An overview of computer programming
    • Not especially difficult
    • One step at a time
    • The hard work is often done for us
  • Memory
    • Random access versus sequential memory
    • Combination random/sequential memory
  • Variables
    • Brief definition of a variable
    • A physical analogy
    • Pretend that you are a computer program
    • Names versus addresses
    • Execute an algorithm
    • Declaring a variable
  • Literals
    • Where does data originate?
    • Hard coded data
    • A value coded into the program
• Preview of the Scratch program
  • The Scratch program named Variable01.sb
    • A variable named Counter (upper-case C)
    • A variable named counter(lower-case c)
• Discussion and sample code
  • No sprites
  • The toolbox buttons
  • The Data toolbox
  • Create two variables
    • Allowable operations for variables
    • Specifying the values
    • Cause the variables to be displayed
    • Create a new variable
    • Allowable variable names and lengths
    • Meaningful variable names
  • Writing the program
    • Programming blocks in the Events category
    • The finished program
  • Behavior of the program
    • Click the green flag
    • Press the space bar
    • Click the mouse on the Stage
  • Event-driven programming
  • Example blocks with pointed ends
• Run the program
• Student programming projects
  • Project 1
  • Project 2
• Summary
• What's next?
• Resources
• Miscellaneous

Preface

Scratch 2.0 (released May 9, 2013) is the second major version of Scratch to be released during the life of the product. Among other things, it features a redesigned editor andwebsite, and allows you to edit projects directly from your web browser.

This module is one in a collection of modules designed to help beginners of all ages (8 and up) learn how to create the code for computer programs using Scratch 2.0 . Information is provided not only for the beginners themselves but also for their parents and teacherswhere appropriate.

The purpose of this module is to teach you about memory, variables, literals, and algorithms in Scratch 2.0 . You will also learn how to write a Scratch program that illustrates the creation and use of variables, case sensitivity, and the ability to detect and respond to mouse and keyboard events.

Student programming projects

In addition to presenting and explaining a Scratch programming project, I will present two student programming projects that are designed to:

• Help the student retain the knowledge gained by studying the module.
• Require the student to think beyond the material presented in the module by requiring the student to answer the question "How do I ...?"

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the imageswhile you are reading about them.

Images

• Image 1 . Cropped image of the Scratch programming interface for the program named Variable01.
• Image 2 . Dialog for entering a variable name.
• Image 3 . Programming blocks in the Events category.
• Image 4 . Example blocks with pointed ends.
• Image 5 . Output from Project 1.
• Image 6 . Output from Project 1.
• Image 7 . Output from Project 2.
• Image 8 . Output from Project 2.