💻 CSE 2100: Live Practical Lab Test Practice Sheet

Exam Context & Environment

In KUET, a standard 2-1 Lab Test gives you 90 minutes to design, implement, compile, and execute a complete C++ program on your terminal, followed by a desk-side viva where the examiner inspects your code architecture, encapsulation, memory handling, and friend/member function designs line-by-line.

• Time Allowed: 90 Minutes | Total Marks: 20
• Structure: Two parallel sets (Set A and Set B) modeled directly on past exam papers.

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📜 General Candidate Instructions

Crucial Lab Rules

1. All data members representing internal states must be securely encapsulated (private or protected). Direct member access in main() results in an automatic 50% penalty.
2. Do not use global variables.
3. Clean compilation is mandatory. Syntax errors preventing compilation will be capped at a maximum of 5 marks.

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📋 SET A: Dynamic Inventory Management System (Warehouse Stock)

❓ Question 1: Class Design & Encapsulation [10 Marks]

Design a class named Product to represent item records inside a warehouse. The class must contain:

• Private Data Members:
  1. productID (integer)
  2. stockCount (integer)
  3. unitPrice (floating-point)
• Public Data Members:
  1. productName (string)
  2. category (string)
• Public Member Functions:
  1. assignInitialValues(int id, string name, string cat, int stock, float price): To initialize all data members.
  2. restock(int qty): Increments stockCount by qty and prints a confirmation.
  3. shipProduct(int qty): Checks if enough stock is available. If yes, decrements stockCount by qty. If not, prints an "Error: Insufficient Stock!" message.
  4. displayDetails() const: Prints the product’s ID, name, category, stock count, and total inventory value (stockCount * unitPrice).

❓ Question 2: Same-Class Friend Comparator [5 Marks]

Declare and define a global friend function named compareInventoryValue(const Product& p1, const Product& p2). This function must compare the total inventory value of both products and return the entire Product object that has the higher total value.

❓ Question 3: Array of Objects & main() Execution [5 Marks]

In the main() function:

1. Declare an array of 3 Product objects (Product warehouse[3];).
2. Write a loop to dynamically populate details for all 3 products from console input.
3. Simulate a shipping transaction of 5 units on the first product (warehouse[0]).
4. Call the friend function compareInventoryValue on the first two products and print the name of the product representing the higher asset value.
5. Loop through and display the final status of all warehouse items.

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📋 SET B: Train Ticket Reservation System (KUET Express)

❓ Question 1: Class Design & Encapsulation [10 Marks]

Design a class named Ticket to manage passenger bookings. The class must contain:

• Private Data Members:
  1. bookingID (integer)
  2. fare (floating-point)
  3. status (character: 'C' for Confirmed, 'P' for Pending)
• Public Data Members:
  1. passengerName (string)
  2. destination (string)
• Public Member Functions:
  1. assignInitialValues(int id, string name, string dest, float price, char stat): To initialize all fields.
  2. confirmBooking(): Changes status to 'C' and prints a confirmation alert.
  3. applyDiscount(float percentage): Deducts the specified percentage from the fare (e.g., entering 10.0 applies a 10% discount).
  4. displayTicket() const: Prints the passenger’s name, destination, fare, and readable status (“Confirmed” or “Pending”).

❓ Question 2: Same-Class Friend Comparator [5 Marks]

Declare and define a global friend function named compareFare(const Ticket& t1, const Ticket& t2). This function must compare the fares of both tickets and return the entire Ticket object representing the more expensive journey.

❓ Question 3: Array of Objects & main() Execution [5 Marks]

In the main() function:

1. Declare an array of 3 Ticket objects (Ticket bookings[3];).
2. Write a loop to dynamically populate booking details for all 3 tickets from console input.
3. Apply a 15% discount to the second ticket (bookings[1]).
4. Compare the tickets of passenger 1 and passenger 2 using compareFare and print the passenger name holding the pricier ticket.
5. Display all ticket details.

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💻 Model Solution Code (Set A: Product Inventory)

#include <iostream>
#include <string>
 
using namespace std;
 
class Product {
private:
    int productID;
    int stockCount;
    float unitPrice;
 
public:
    string productName;
    string category;
 
    // 1. Assign Initial Values
    void assignInitialValues(int id, string name, string cat, int stock, float price) {
        productID = id;
        productName = name;
        category = cat;
        stockCount = stock;
        unitPrice = price;
    }
 
    // 2. Restock Operation
    void restock(int qty) {
        if (qty > 0) {
            stockCount += qty;
            cout << "Successfully restocked " << qty << " units of " << productName << endl;
        }
    }
 
    // 3. Ship/Sell Operation
    void shipProduct(int qty) {
        if (qty <= stockCount) {
            stockCount -= qty;
            cout << "Successfully shipped " << qty << " units of " << productName << endl;
        } else {
            cout << "Error: Insufficient Stock for " << productName << "! Available: " << stockCount << endl;
        }
    }
 
    // Helper getter for total inventory value
    float getInventoryValue() const {
        return stockCount * unitPrice;
    }
 
    // 4. Display Details
    void displayDetails() const {
        cout << "ID: " << productID
             << " | Name: " << productName
             << " | Category: " << category
             << " | Stock: " << stockCount
             << " | Value: $" << getInventoryValue() << endl;
    }
 
    // DECLARING SAME-CLASS FRIEND COMPARATOR
    friend Product compareInventoryValue(const Product& p1, const Product& p2);
};
 
// DEFINING FRIEND FUNCTION (Global scope: no ClassName:: and no friend keyword)
Product compareInventoryValue(const Product& p1, const Product& p2) {
    if (p1.getInventoryValue() >= p2.getInventoryValue()) {
        return p1; // Returns the entire Product object by value
    } else {
        return p2;
    }
}
 
int main() {
    Product warehouse[3]; // Array of 3 Objects
 
    // 1. Dynamic Input Loop
    cout << "=== REGISTER WAREHOUSE PRODUCTS ===" << endl;
    for (int i = 0; i < 3; i++) {
        int id, stock;
        string name, cat;
        float price;
 
        cout << "\nEnter Details for Product #" << (i + 1) << endl;
        cout << "Enter Product ID: ";
        cin >> id;
        cin.ignore(); // Clear newline character from input buffer
 
        cout << "Enter Product Name: ";
        getline(cin, name);
 
        cout << "Enter Category: ";
        getline(cin, cat);
 
        cout << "Enter Stock Count: ";
        cin >> stock;
 
        cout << "Enter Unit Price: ";
        cin >> price;
 
        warehouse[i].assignInitialValues(id, name, cat, stock, price);
    }
 
    // 2. Simulate Shipping Transaction on first product
    cout << "\n=== SIMULATING TRANSACTION ===" << endl;
    warehouse[0].shipProduct(5); // Attempt to ship 5 units
 
    // 3. Compare Values using Friend Function
    cout << "\n=== COMPARING INVENTORY VALUES ===" << endl;
    Product higherValued = compareInventoryValue(warehouse[0], warehouse[1]);
    cout << "The higher asset-valued product between \"" << warehouse[0].productName
         << "\" and \"" << warehouse[1].productName << "\" is: " << higherValued.productName
         << " (Total Value: $" << higherValued.getInventoryValue() << ")" << endl;
 
    // 4. Final Display Report
    cout << "\n=== FINAL INVENTORY REPORT ===" << endl;
    for (int i = 0; i < 3; i++) {
        warehouse[i].displayDetails();
    }
 
    return 0;
}

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⚠️ Examiner’s Viva Check: Top 3 Desk-Side Traps

Viva Question 1: Friend Function Signature

“Show me your friend function signature. Why does it take two arguments instead of one?”

• Answer: A friend function is a non-member global function, so it does not receive an implicit this pointer (lesson-5-advanced-inheritance, lesson-6-this-and-operators). Thus, to compare two objects, both must be explicitly passed as parameters. (If it were a member function, it would take only one argument because the invoking object acts as the left-hand side).

Viva Question 2: Pass-by-Const-Reference vs. Pass-by-Value

“What is the performance implication of passing Product p1 by value versus const Product& p1?”

• Answer: Passing by value (Product p1) invokes the copy constructor (lesson-3-object-lifecycle), making redundant temporary stack copies of member strings and integers. Passing by const reference (const Product& p1) passes only a memory address (zero copying overhead) while const guarantees read-only safety (lesson-2-member-functions-and-arrays).

Viva Question 3: The cin.ignore() Buffer Flush

“Why did you place cin.ignore() immediately after cin >> id and before getline(cin, name)?”

• Answer: Standard extraction (cin >> id) leaves a trailing newline character \n in the input stream buffer. If not discarded with cin.ignore(), the subsequent getline() immediately reads that trailing newline as an empty string, skipping user input for the name (lesson-1-intro-to-oop-and-classes).