Airline Reservation System

A beginner-friendly C++ OOP project demonstrating core object-oriented programming concepts

Project Description

This is a terminal-based airline reservation system built in pure standard C++ to demonstrate fundamental Object-Oriented Programming (OOP) concepts. The system allows users to view flights, search by route, book seats, cancel bookings, view tickets, and see passenger manifests.

The project is designed for learning purposes with:

Every line of code commented for educational clarity
Beginner-friendly syntax with no complex expressions
Pure C++ only - no external libraries or frameworks
Fixed-size arrays instead of STL containers
No dynamic memory allocation (no new/delete)

How to Compile

Use the standard g++ compiler with this simple command:

g++ main.cpp -o airline

Requirements:

g++ compiler (any standard version)
No external libraries needed
Works on Linux, macOS, and Windows (with MinGW)

How to Run

After compiling, run the program:

./airline

On Windows:

airline.exe

File Structure

The project consists of exactly 4 source files plus 1 data file:

main.cpp - Entry point containing only the main() function and includes
classes.h - All 13 classes plus 8 exception classes
helpers.h - All helper functions with exception handling
README.md - This documentation file
airline_data.txt - Auto-generated data file (created on first exit)

OOP Concepts Demonstrated

This project demonstrates all major OOP concepts required for an intermediate-level C++ course:

1. Classes and Objects

13 classes representing real-world entities
Objects created and used throughout the program

2. Encapsulation

All data members are private
Public getter and setter methods for controlled access
Implementation details hidden from outside code

3. Constructor Overloading

Default constructors (no parameters)
Parameterized constructors (with initialization values)
Every class demonstrates constructor overloading

4. Copy Constructor

Implemented in Passenger and Flight classes
Creates deep copies of objects safely

5. Arrays of Objects

Flight contains arrays of Seat[] and Booking[]
Airline contains array of Flight[]
Demonstrates composition relationships

6. Static Class Members

Booking::bookingCounter - shared counter for generating unique PNR numbers
Airline::totalAirlinesCreated - tracks total airline objects created
Static member functions to access static data

7. Inheritance - Single Level

Admin inherits from User (User → Admin)
Customer inherits from User (User → Customer)
CashPayment inherits from Payment (Payment → CashPayment)
LoyaltyPayment inherits from Payment (Payment → LoyaltyPayment)

8. Inheritance - Multi-Level

Payment → OnlinePayment → CreditCardPayment
Three-level inheritance chain demonstrating hierarchical relationships

9. Protected Members

User base class uses protected members
Accessible in derived classes (Admin, Customer)
Not accessible from outside the class hierarchy

10. Polymorphism

Virtual functions in base classes
Overridden methods in derived classes
Runtime polymorphism demonstrated in OOP demo menus

11. Operator Overloading

Booking class overloads the == operator
Allows comparing two bookings by their PNR number

12. Friend Functions

showLoyaltyPointsUsed() is a friend of LoyaltyPayment
Accesses private pointsUsed member directly
Demonstrates controlled access to private data

13. Abstraction

Complex operations hidden inside class methods
Simple public interfaces for users of the classes

14. Composition

Flight HAS-A Seat[] array (composition)
Flight HAS-A Booking[] array (composition)
Airline HAS-A Flight[] array (composition)
Booking HAS-A Passenger object (composition)

15. Exception Handling

Custom exception class hierarchy (AirlineException base class)
7 derived exception classes for specific error types
Try-catch blocks protecting all critical operations
Graceful error handling with clear user messages

16. File Handling

Data persistence using fstream (file input/output)
Saves all flight, seat, and booking data to text file
Loads data on program startup
Booking counter persists across program runs
Graceful fallback to sample data if file missing

Class List

The system contains 13 main classes plus 8 exception classes:

Main Classes:

Passenger - Stores passenger information (name, age, ID)
Seat - Represents one seat on a flight (number, class, availability, price)
Booking - Stores one reservation (PNR, passenger, seat, payment)
Flight - Represents one flight with seats and bookings
Airline - Manages multiple flights
User - Base class for all system users
Admin - Inherits from User, represents admin users
Customer - Inherits from User, represents customer users
Payment - Base class for all payment methods
OnlinePayment - Inherits from Payment, base for online payments
CreditCardPayment - Inherits from OnlinePayment (multi-level)
CashPayment - Inherits from Payment, handles cash transactions
LoyaltyPayment - Inherits from Payment, handles points redemption

Exception Classes:

AirlineException - Base exception class for all errors
InputException - Invalid user input errors
FlightNotFoundException - Flight not found errors
SeatUnavailableException - No seats available errors
BookingNotFoundException - Booking/PNR not found errors
ArrayFullException - Array capacity reached errors
FileIOException - File read/write errors
PaymentException - Payment validation/processing errors

Features

Main Features:

View All Flights - Display all available flights with details
Search Flights by Route - Find flights from origin to destination
Book a Seat - Complete booking process with payment
Cancel a Booking - Cancel using PNR number
View Booking Details - Display formatted boarding pass ticket
View Passenger Manifest - Show all passengers on a flight

Payment Methods:

Credit Card Payment (demonstrates multi-level inheritance)
Cash Payment (with change calculation)
Loyalty Points Payment (with friend function demonstration)

Data Persistence:

Auto-save on Exit - All data saved to airline_data.txt
Auto-load on Startup - Previous session data restored
Persistent PNR Numbers - Booking counter never resets
Graceful Fallback - Loads sample data if file missing

Exception Handling:

Input Validation - All user inputs protected with exceptions
Error Recovery - Program never crashes on bad input
Clear Error Messages - Every error displays helpful message
File Error Handling - Graceful handling of file I/O errors

Additional Features:

View User Profiles - Display sample admin and customer account information
View Payment Options - Demonstration of different payment processing methods

Sample Data

The system loads 3 sample flights on startup:

PK-301: Lahore → Karachi (2026-06-01, 10:00-12:00, 18 seats)
PK-502: Islamabad → Dubai (2026-06-05, 14:00-17:30, 18 seats)
PK-786: Karachi → London (2026-06-10, 22:00-06:00, 18 seats)

Each flight has:

14 Economy seats (Rs. 5,000 each)
4 Business seats (Rs. 12,000 each)

Usage Example

==========================================
      AIRLINE RESERVATION SYSTEM
==========================================
  1. View All Flights
  2. Search Flights by Route
  3. Book a Seat
  4. Cancel a Booking
  5. View Booking Details (Ticket)
  6. View Passenger Manifest
  7. Demo: User Hierarchy (OOP)
  8. Demo: Payment Methods (OOP)
  0. Exit
==========================================
Enter your choice : 3

==========================================
  BOOK A SEAT
==========================================
Enter flight number (e.g. PK-301) : PK-301
Enter passenger full name : Ali Ahmed
Enter passenger age       : 28
Enter passenger ID / Passport : PK-1234567
Enter seat class (economy / business) : economy

Payment Method:
  1. Credit Card
  2. Cash
  3. Loyalty Points
Enter your choice (1-3) : 2

Cash payment of Rs.5000 received.
Change returned: Rs.500.

==========================================
  BOOKING CONFIRMED
==========================================
  PNR Number  : PNR001
  Seat Number : 1
  Seat Class  : Economy
  Amount Paid : Rs.5000
  SAVE YOUR PNR NUMBER FOR FUTURE USE!
==========================================

Code Quality Standards

This project follows strict coding standards for educational purposes:

✅ Every line has a comment explaining what it does
✅ No abbreviations - all variable names are full English words
✅ No pointers except where absolutely necessary
✅ No dynamic memory - all objects on the stack
✅ Fixed array sizes defined as constants
✅ Input validation on all user inputs
✅ Clean terminal output with separators and formatting
✅ Beginner-friendly syntax - no complex expressions

Learning Objectives

After studying this project, you will understand:

How to design classes for real-world entities
How to implement encapsulation with private data and public methods
How to use inheritance to create class hierarchies
How to implement polymorphism with virtual functions
How to overload operators for custom behavior
How to use friend functions for controlled access
How to manage relationships between classes (composition)
How to use static members for class-level data
How to implement exception handling with custom exception classes
How to implement file I/O for data persistence
How to write clean, commented, beginner-friendly code

Project Constraints

This project intentionally follows these constraints for educational purposes:

Only 4 headers allowed: <iostream>, <string>, <cstring>, <fstream>
No STL containers: No vectors, maps, lists, etc.
No dynamic memory: No new or delete keywords
Fixed arrays only: All collections use plain C++ arrays
No external libraries: Pure standard C++ only
Exactly 4 source files: main.cpp, classes.h, helpers.h, README.md
1 data file: airline_data.txt (auto-generated)

Author

OOP Project - Airline Reservation System
Created for educational purposes to demonstrate C++ OOP concepts
Date: 2026-05-05

License

This is an educational project. Feel free to use it for learning purposes.

End of README

Name		Name	Last commit message	Last commit date
Latest commit History 26 Commits
CLAUDE.md		CLAUDE.md
FLOW.md		FLOW.md
README.md		README.md
airline		airline
airline.exe		airline.exe
classes.h		classes.h
helpers.h		helpers.h
main.cpp		main.cpp

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