Session 6: Introduction to Decision Making

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Session 6: Introduction to Decision Making

Weekend Session 1.5 hours Phase 2: Control Structures

Learn conditional statements and decision making. Create programs that respond differently to user input.

🎯 Key Skills You'll Learn:

  • if, else if, else statements
  • Comparison operators
  • Logical operators
  • Boolean logic

🚀 Session Project:

Rock, Paper, Scissors Game

Learning Objectives

  • Understand conditional statements and decision making
  • Learn the if, else if, and else statements
  • Create programs that respond differently to user input
  • Understand boolean logic and comparisons

Warm-up (10 minutes)

Think about decisions you make every day:

  • If it’s raining, I bring an umbrella
  • If I’m hungry, I eat food
  • If it’s weekend, I sleep in

How would you teach a computer to make these same decisions?

New Concept Introduction (30 minutes)

What are Conditional Statements?

Conditional statements let programs make decisions based on different situations. Just like you decide what to wear based on the weather, programs can decide what to do based on user input or calculations.

Basic if Statement

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#include <iostream>
using namespace std;

int main() {
    int age;
    cout << "Enter your age: ";
    cin >> age;
    
    if (age >= 18) {
        cout << "You are an adult!" << endl;
    }
    
    return 0;
}

if-else Statement

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#include <iostream>
using namespace std;

int main() {
    int age;
    cout << "Enter your age: ";
    cin >> age;
    
    if (age >= 18) {
        cout << "You are an adult!" << endl;
    } else {
        cout << "You are a minor." << endl;
    }
    
    return 0;
}

if-else if-else Chain

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#include <iostream>
using namespace std;

int main() {
    int score;
    cout << "Enter your test score: ";
    cin >> score;
    
    if (score >= 90) {
        cout << "Grade: A" << endl;
    } else if (score >= 80) {
        cout << "Grade: B" << endl;
    } else if (score >= 70) {
        cout << "Grade: C" << endl;
    } else if (score >= 60) {
        cout << "Grade: D" << endl;
    } else {
        cout << "Grade: F" << endl;
    }
    
    return 0;
}

Comparison Operators

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// Equal to
if (age == 18) { /* exactly 18 */ }

// Not equal to
if (age != 18) { /* not 18 */ }

// Greater than
if (age > 18) { /* older than 18 */ }

// Less than
if (age < 18) { /* younger than 18 */ }

// Greater than or equal to
if (age >= 18) { /* 18 or older */ }

// Less than or equal to
if (age <= 18) { /* 18 or younger */ }

Important: = vs ==

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int x = 5;     // Assignment: give x the value 5
if (x == 5)    // Comparison: check if x equals 5

Logical Operators

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// AND (&&) - both conditions must be true
if (age >= 13 && age <= 19) {
    cout << "You are a teenager!" << endl;
}

// OR (||) - at least one condition must be true
if (day == "Saturday" || day == "Sunday") {
    cout << "It's weekend!" << endl;
}

// NOT (!) - opposite of the condition
if (!(age < 18)) {  // same as age >= 18
    cout << "You are an adult!" << endl;
}

Hands-on Practice (40 minutes)

Exercise 1: Simple Password Checker (15 minutes)

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#include <iostream>
#include <string>
using namespace std;

int main() {
    string password;
    cout << "Enter the password: ";
    cin >> password;
    
    if (password == "secret123") {
        cout << "Access granted!" << endl;
    } else {
        cout << "Access denied!" << endl;
    }
    
    return 0;
}

Exercise 2: Number Guessing Game (15 minutes)

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#include <iostream>
using namespace std;

int main() {
    int secretNumber = 42;
    int guess;
    
    cout << "I'm thinking of a number between 1 and 100." << endl;
    cout << "What's your guess? ";
    cin >> guess;
    
    if (guess == secretNumber) {
        cout << "Congratulations! You got it!" << endl;
    } else if (guess < secretNumber) {
        cout << "Too low! The number was " << secretNumber << endl;
    } else {
        cout << "Too high! The number was " << secretNumber << endl;
    }
    
    return 0;
}

Exercise 3: Grade Calculator with Feedback (10 minutes)

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#include <iostream>
using namespace std;

int main() {
    double score;
    cout << "Enter your test score (0-100): ";
    cin >> score;
    
    if (score >= 90) {
        cout << "Grade: A - Excellent work!" << endl;
    } else if (score >= 80) {
        cout << "Grade: B - Good job!" << endl;
    } else if (score >= 70) {
        cout << "Grade: C - Satisfactory" << endl;
    } else if (score >= 60) {
        cout << "Grade: D - Needs improvement" << endl;
    } else {
        cout << "Grade: F - Please see me after class" << endl;
    }
    
    return 0;
}

Challenge/Quiz (10 minutes)

Challenge: Rock, Paper, Scissors Game Create a program that:

  1. Asks the user to enter their choice (rock, paper, or scissors)
  2. The computer randomly chooses (for now, just pick one - we’ll learn random later)
  3. Determines the winner based on the rules:
    • Rock beats Scissors
    • Scissors beats Paper
    • Paper beats Rock
    • Same choices = Tie
  4. Displays both choices and announces the winner

Validation Prompt

🤖 AI Validation Prompt

Copy this prompt and your code to ChatGPT or Claude for instant feedback:


```
I'm learning C++ and just completed Session 6. Here's my solution to the Rock, Paper, Scissors challenge:

[PASTE YOUR CODE HERE]

The challenge was: Create a Rock, Paper, Scissors game that compares user input with a computer choice and determines the winner.

Please check if my solution:
1. Uses if-else statements correctly
2. Implements the game rules properly
3. Handles string comparisons correctly
4. Displays clear output showing both choices and the result
5. Uses logical operators appropriately

If there are issues, please explain what's wrong and give me a hint to fix it (don't give me the complete solution).
```

What You Learned

  • ✅ If, else if, and else statements
  • ✅ Comparison operators (==, !=, <, >, <=, >=)
  • ✅ Logical operators (&&, ||, !)
  • ✅ Boolean logic and decision making
  • ✅ Creating interactive programs that respond to input

Next Session Preview

In Session 7, you’ll learn about nested conditions and more complex decision-making scenarios!

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