Day 2: Variables and Assignments

Learning Objectives

• AAP-1.A: Represent a value with a variable.
• AAP-1.B: Determine the value of a variable as a result of an assignment.
• AAP-1.C: Represent a list or string using a variable.

Essential Questions

• How do computers store and manipulate data?
• How do variables help us represent and work with data in programs?

Materials Needed

• Presentation slides on variables and assignments
• Programming environment (block-based or text-based)
• Variable practice worksheet
• Exit ticket templates
• Sticky notes for concept check

Vocabulary

• Variable
• Assignment
• Data type
• Integer
• String
• Boolean
• List
• Declaration
• Initialization

Procedure (50 minutes)

Opening (8 minutes)

1. Review and Connection (3 minutes)

   • Review algorithm concepts from previous lesson
   • Connect to today's focus on variables as a way to store data in programs

2. Warm-up Activity (5 minutes)

   • Display a simple program with variables and ask students to predict what it does
   • Discuss initial thoughts about how the computer keeps track of values

Main Activities (32 minutes)

3. Lecture: Variables, Data Types, and Assignments (12 minutes)

   • Define variables as abstractions that hold values in a program
   • Explain different data types:
     • Numbers (integers, decimals)
     • Strings (text)
     • Booleans (true/false)
     • Lists (collections of values)
   • Demonstrate variable declaration and assignment
   • Explain the assignment operator (←) and how it works
   • Discuss the importance of meaningful variable names
   • Show how the same variable can hold different values over time

4. Demo: How Variables Store and Update Values (8 minutes)

   • Use a visual representation of memory to show how variables work
   • Demonstrate step-by-step execution of code with variable assignments
   • Show examples of:
     • Simple assignment (a ← 5)
     • Assignment from another variable (b ← a)
     • Reassignment (a ← 7)
     • Assignment with expressions (c ← a + b)
   • Emphasize that variables hold the most recent value assigned

5. Hands-on: Declaring Variables and Assigning Values (12 minutes)

   • Students work in the programming environment
   • Guide students through creating variables of different types
   • Have students write and test code with variable assignments
   • Students trace code execution and predict final variable values
   • Include examples with multiple assignments and expressions

Closing (10 minutes)

6. Activity: Trace Code with Variable Assignments (5 minutes)

   • Provide students with a code segment containing multiple variable assignments
   • Students trace the code step by step, recording the value of each variable after each statement
   • Discuss the final values and any common misconceptions

7. Exit Ticket and Preview (5 minutes)

   • Students complete exercises involving variable declarations and assignments
   • Preview that next class will focus on expressions and operators

Assessment

• Formative: Participation in hands-on activities and code tracing
• Exit Ticket: Accuracy of variable assignment exercises

Differentiation

For Advanced Students

• Provide more complex assignment scenarios
• Introduce additional data types or type conversion
• Challenge them to create a program that uses multiple variable types

For Struggling Students

• Provide a visual reference for how assignment works
• Use simpler examples with fewer variables
• Offer a step-by-step template for tracing code

Homework/Extension

• Complete a worksheet with variable declaration and assignment exercises
• Write a short program that uses variables to store and manipulate personal data (age, name, etc.)
• Research how different programming languages handle variable declarations and types

Teacher Notes

• Emphasize that variables in memory are different from variables in algebra
• Watch for confusion about the assignment operator (← is not the same as = in mathematics)
• Make connections to how variables will be used in future programming tasks
• Consider using physical props (boxes with labels) to demonstrate variable concepts
• Remind students that understanding variables is fundamental to all programming