diff --git a/OOP_POP_Exercises 1-3_JC.playground/Contents.swift b/OOP_POP_Exercises 1-3_JC.playground/Contents.swift
new file mode 100644
index 0000000..390e1a1
--- /dev/null
+++ b/OOP_POP_Exercises 1-3_JC.playground/Contents.swift	
@@ -0,0 +1,313 @@
+import UIKit
+
+// MARK: - Exercise 1: Social Media Post
+
+class Post {
+    var author: String
+    var content: String
+    var likes: Int
+    
+    init(author: String, content: String, likes: Int = 0) {
+        self.author = author
+        self.content = content
+        self.likes = likes
+    }
+    
+    func display() {
+        print("Post by \(author):")
+        print("\"\(content)\"")
+        print("Likes: \(likes)")
+        print(String(repeating: "-", count: 30)) // Separator line for better readability
+    }
+}
+
+// MARK: - Main program functionality
+
+func main() {
+    // Create first post
+    let post1 = Post(author: "Alice", content: "Just finished my first iOS assignment!", likes: 15)
+    
+    // Create second post
+    let post2 = Post(author: "Bob", content: "Learning Swift classes is fun!", likes: 7)
+    
+    // Display both posts
+    post1.display()
+    post2.display()
+}
+
+// Calling the main function
+main()
+
+
+// MARK: - Exercise 2: Using the Singleton Pattern to create a more flexible shopping cart system
+
+// Product Class
+class Product {
+    let name: String
+    let price: Double
+    var quantity: Int
+    
+    init(name: String, price: Double, quantity: Int = 1) {
+        self.name = name
+        self.price = price
+        self.quantity = quantity
+    }
+}
+
+//MARK: - DiscountStrategy Protocol and Implementations
+
+protocol DiscountStrategy {
+    func calculateDiscount(total: Double) -> Double
+}
+
+class NoDiscountStrategy: DiscountStrategy {
+    func calculateDiscount(total: Double) -> Double {
+        return 0.0 // No discount
+    }
+}
+
+class PercentageDiscountStrategy: DiscountStrategy {
+    let percentage: Double
+    
+    init(percentage: Double) {
+        self.percentage = min(percentage, 100.0) // Ensure discount doesn't exceed 100%
+    }
+    
+    func calculateDiscount(total: Double) -> Double {
+        return total * (percentage / 100.0)
+    }
+}
+
+//MARK: - ShoppingCartSingleton Class
+
+class ShoppingCartSingleton {
+    // Static property for the singleton instance
+    private static var instance: ShoppingCartSingleton?
+    
+    // Private array to store products (composition)
+    private var products: [Product] = []
+    
+    // Discount strategy
+    var discountStrategy: DiscountStrategy = NoDiscountStrategy()
+    
+    // Private initializer to enforce singleton pattern
+    private init() {}
+    
+    // Method to access the singleton instance
+    static func sharedInstance() -> ShoppingCartSingleton {
+        if instance == nil {
+           instance = ShoppingCartSingleton()
+        }
+        return instance!
+    }
+    
+    // Method to add a product to the cart
+    func addProduct(product: Product, quantity: Int = 1) {
+        // Check if the product is already in the cart
+        if let index = products.firstIndex(where: { $0.name == product.name }) {
+            // If it is, update the quantity
+            products[index].quantity += quantity
+        } else {
+            // If not, add the product with the specified quantity
+            let newProduct = Product(name: product.name, price: product.price, quantity: quantity)
+            products.append(newProduct)
+        }
+    }
+    
+    // Method to remove a product from the cart
+    func removeProduct(product: Product) {
+        products.removeAll { $0.name == product.name }
+    }
+    
+    // Method to clear the cart
+    func clearCart() {
+        products.removeAll()
+    }
+    
+    // Method to calculate the total price
+    func getTotalPrice() -> Double {
+        let subtotal = products.reduce(0.0) { $0 + ($1.price * Double($1.quantity)) }
+        let discount = discountStrategy.calculateDiscount(total: subtotal)
+        return subtotal - discount
+    }
+    
+    // Helper method to display cart contents
+    func displayCart() {
+        if products.isEmpty {
+            print("Shopping cart is empty.")
+            return
+        }
+        
+        print("Shopping Cart Contents:")
+        print("------------------------")
+        for product in products {
+            print("\(product.name) - $\(product.price) x \(product.quantity) = $\(product.price * Double(product.quantity))")
+        }
+        
+        let subtotal = products.reduce(0.0) { $0 + ($1.price * Double($1.quantity)) }
+        let discount = discountStrategy.calculateDiscount(total: subtotal)
+        
+        print("------------------------")
+        print("Subtotal: $\(subtotal)")
+        print("Discount: $\(discount)")
+        print("Total: $\(getTotalPrice())")
+        print("------------------------")
+    }
+}
+
+//MARK: - Example Usage
+
+func mainexample() {
+    // Singleton pattern to shopping cart instance
+    let cart = ShoppingCartSingleton.sharedInstance()
+    
+    // Example product creation
+    let laptop = Product(name: "Laptop", price: 1299.99)
+    let phone = Product(name: "Smartphone", price: 599.99)
+    let charger = Product(name: "USB-C Charger", price: 19.99)
+    
+    // Adding products to the cart
+    cart.addProduct(product: laptop)
+    cart.addProduct(product: phone, quantity: 2)
+    cart.addProduct(product: charger, quantity: 3)
+    
+    // Displaying the cart with no discount
+    print("Cart with no discount:")
+    cart.displayCart()
+    
+    // Applying a 10% discount
+    cart.discountStrategy = PercentageDiscountStrategy(percentage: 10.0)
+    print("\nCart with 10% discount:")
+    cart.displayCart()
+    
+    // Removing a product
+    cart.removeProduct(product: phone)
+    print("\nCart after removing smartphones:")
+    cart.displayCart()
+    
+    // Clearing the cart
+    cart.clearCart()
+    print("\nCart after clearing:")
+    cart.displayCart()
+}
+
+// Running the example usage
+main()
+
+// MARK: - Exercise 3: Payment System Model & Custom Error Type for Payment Processing
+
+enum PaymentError: Error {
+    case insufficientFunds
+    case invalidCard
+    case cardExpired
+    case networkError
+    case paymentLimitExceeded
+    case cashRegisterEmpty
+    
+    var message: String {
+        switch self {
+        case .insufficientFunds:
+            return "Insufficient funds to complete the transaction."
+        case .invalidCard:
+            return "The card information is invalid."
+        case .cardExpired:
+            return "The card has expired."
+        case .networkError:
+            return "Network error occurred during payment processing."
+        case .paymentLimitExceeded:
+            return "The payment amount exceeds the allowed limit."
+        case .cashRegisterEmpty:
+            return "Cash register is empty and cannot provide change."
+        }
+    }
+}
+
+// MARK: - Payment Processor Protocol
+
+protocol PaymentProcessor {
+    func processPayment(amount: Double) throws
+    var name: String { get }
+}
+
+// MARK: - Credit Card Processor
+
+class CreditCardProcessor: PaymentProcessor {
+    let name = "Credit Card"
+    private let cardNumber: String
+    private let expiryDate: String
+    private let cvv: String
+    private let balance: Double
+    
+    init(cardNumber: String, expiryDate: String, cvv: String, balance: Double) {
+        self.cardNumber = cardNumber
+        self.expiryDate = expiryDate
+        self.cvv = cvv
+        self.balance = balance
+    }
+    
+    func processPayment(amount: Double) throws {
+        // Validate the amount
+        if amount <= 0 {
+            throw PaymentError.invalidCard
+        }
+        
+        // Check for payment limits
+        if amount > 10000 {
+            throw PaymentError.paymentLimitExceeded
+        }
+        
+        // Simulate card validation
+        if cardNumber.count != 16 {
+            throw PaymentError.invalidCard
+        }
+        
+        // Simulate expiry date check (very basic simulation)
+        if expiryDate == "01/20" {
+            throw PaymentError.cardExpired
+        }
+        
+        // Check for sufficient funds
+        if amount > balance {
+            throw PaymentError.insufficientFunds
+        }
+        
+        // Simulate random network error (10% chance)
+        if Double.random(in: 0...1) < 0.1 {
+            throw PaymentError.networkError
+        }
+        
+        // If we reach here, payment is successful
+        print("Credit card payment of $\(amount) processed successfully.")
+    }
+}
+
+// MARK: - Cash Processor
+
+class CashProcessor: PaymentProcessor {
+    let name = "Cash"
+    private var cashInRegister: Double
+    
+    init(cashInRegister: Double) {
+        self.cashInRegister = cashInRegister
+    }
+    
+    func processPayment(amount: Double) throws {
+        // Validating the amount
+        if amount <= 0 {
+            throw PaymentError.invalidCard  // Reusing error for simplicity
+        }
+        
+        // Check if providing change is possible
+        if cashInRegister < amount {
+            throw PaymentError.cashRegisterEmpty
+        }
+        
+        // Processing payment
+        cashInRegister -= amount
+        
+        // If below messages display, payment is successful
+        print("Cash payment of $\(amount) processed successfully.")
+        print("Remaining cash in register: $\(cashInRegister)")
+    }
+}
+
diff --git a/OOP_POP_Exercises 1-3_JC.playground/contents.xcplayground b/OOP_POP_Exercises 1-3_JC.playground/contents.xcplayground
new file mode 100644
index 0000000..7f43ce8
--- /dev/null
+++ b/OOP_POP_Exercises 1-3_JC.playground/contents.xcplayground	
@@ -0,0 +1,2 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='7.0' target-platform='ios' swift-version='6' buildActiveScheme='true' importAppTypes='true'/>
\ No newline at end of file
diff --git a/OOP_POP_Exercises 1-3_JC.playground/playground.xcworkspace/contents.xcworkspacedata b/OOP_POP_Exercises 1-3_JC.playground/playground.xcworkspace/contents.xcworkspacedata
new file mode 100644
index 0000000..ca3329e
--- /dev/null
+++ b/OOP_POP_Exercises 1-3_JC.playground/playground.xcworkspace/contents.xcworkspacedata	
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "group:">
+   </FileRef>
+</Workspace>
diff --git a/OOP_POP_Exercises 1-3_JC.playground/playground.xcworkspace/xcuserdata/jdelacuesta.xcuserdatad/UserInterfaceState.xcuserstate b/OOP_POP_Exercises 1-3_JC.playground/playground.xcworkspace/xcuserdata/jdelacuesta.xcuserdatad/UserInterfaceState.xcuserstate
new file mode 100644
index 0000000..a4c6a7c
Binary files /dev/null and b/OOP_POP_Exercises 1-3_JC.playground/playground.xcworkspace/xcuserdata/jdelacuesta.xcuserdatad/UserInterfaceState.xcuserstate differ