Variables and Data Types

📦 What are Variables?

Variables are containers that store data in your programs. Think of them as labeled boxes where you can put values and retrieve them later. Variables are fundamental to programming because they allow your programs to work with data dynamically.

🔤 Declaring Variables

iPseudo offers three flexible ways to declare variables:

Style 1: Using var Keyword (Recommended)

Algorithm VarExample

var studentName = "Alice"
var studentAge = 20
var studentGPA = 3.75
var isEnrolled = true

Print "Name:", studentName
Print "Age:", studentAge
Print "GPA:", studentGPA
Print "Enrolled:", isEnrolled

Endalgorithm

Style 2: Using Variable Keyword

Algorithm VariableKeywordExample

Variable productName = "Laptop"
Variable productPrice = 999.99
Variable inStock = true

Print productName, "costs $", productPrice

Endalgorithm

Style 3: Using Declare As (Typed)

Algorithm TypedVariables

Declare name As String
Declare age As Integer
Declare salary As Float

Set "Bob" To name
Set 30 To age
Set 50000.50 To salary

Print name, "is", age, "years old"

Endalgorithm

Data Types

Data types define what kind of data a variable can hold. iPseudo supports several fundamental types:

1. Integer (Whole Numbers)

Integers are whole numbers without decimal points.

Algorithm IntegerExample

var age = 25
var temperature = -5
var studentCount = 150
var year = 2025

Print "Age:", age
Print "Temperature:", temperature, "°C"
Print "Students:", studentCount
Print "Year:", year

Endalgorithm

Use integers for:

• Counting items
• Age, year, day numbers
• Array indices
• Loop counters

2. Float (Decimal Numbers)

Floats are numbers with decimal points, used for precise calculations.

Algorithm FloatExample

var price = 19.99
var temperature = 98.6
var pi = 3.14159
var percentage = 87.5

Print "Price: $", price
Print "Body temp:", temperature, "°F"
Print "Pi ≈", pi
Print "Score:", percentage, "%"

Endalgorithm

Use floats for:

• Money and prices
• Measurements and distances
• Scientific calculations
• Percentages and ratios

3. String (Text)

Strings are sequences of characters enclosed in quotes.

Algorithm StringExample

var firstName = "John"
var lastName = "Smith"
var email = "john@example.com"
var message = "Hello, World!"

# String concatenation
var fullName = firstName + " " + lastName

Print "Full Name:", fullName
Print "Email:", email
Print message

Endalgorithm

Use strings for:

• Names and text
• Messages and descriptions
• Email addresses and URLs
• Any textual data

4. Boolean (True/False)

Booleans have only two possible values: true or false.

Algorithm BooleanExample

var isStudent = true
var hasLicense = false
var isAdult = true

Print "Is student:", isStudent
Print "Has license:", hasLicense
Print "Is adult:", isAdult

# Booleans from comparisons
var age = 20
var canVote = age >= 18
Print "Can vote:", canVote

Endalgorithm

Use booleans for:

• Yes/No questions
• On/Off states
• Condition results
• Flags and switches

🔄 Updating Variables

Once created, you can change a variable's value:

Algorithm UpdateVariables

# Create variable
var score = 0
Print "Initial score:", score

# Update variable
score = 10
Print "After first update:", score

# Update again
score = 25
Print "After second update:", score

# Increment variable
score = score + 5
Print "After increment:", score

Endalgorithm

Variable Naming Rules

✅ Valid Variable Names:

• age - Simple lowercase
• studentName - camelCase (recommended)
• first_name - snake_case
• age2 - Can include numbers
• totalScore - Descriptive

❌ Invalid Variable Names:

• 2age - Can't start with number
• student-name - No hyphens
• first name - No spaces
• total$ - No special characters

Real-World Example

Algorithm ShoppingCart

# Product details
var productName = "Laptop"
var productPrice = 999.99
var quantity = 2
var taxRate = 0.08

# Calculate totals
var subtotal = productPrice * quantity
var tax = subtotal * taxRate
var total = subtotal + tax

# Display receipt
Print "================================"
Print "       SHOPPING RECEIPT"
Print "================================"
Print "Product:", productName
Print "Price:", productPrice
Print "Quantity:", quantity
Print "--------------------------------"
Print "Subtotal: $", subtotal
Print "Tax: $", tax
Print "================================"
Print "TOTAL: $", total
Print "================================"

Endalgorithm

📋 Quick Reference

Key Takeaways

• ✅ Variables store data that your program can use and modify
• ✅ Use var, Variable, or Declare As to create variables
• ✅ Choose the right data type for your data (Integer, Float, String, Boolean)
• ✅ Use descriptive names that explain what the variable represents
• ✅ Variables can be updated throughout your program
• ✅ Follow naming rules (no spaces, no special characters, can't start with numbers)

💪 Practice Exercises