Unit 1: Principles of OOP

In procedural programming (C), a program is a list of functions working on shared data. As programs grow, any function can change any data, which makes them hard to maintain. OOP solves this by combining data and functions into objects and controlling access to the data.

• Reusability through inheritance — write once, extend many times.
• Data security through encapsulation and data hiding.
• Easier maintenance and modelling of real-world entities (Student, Account, Car).
• Extensibility — new features can be added with little change to existing code.

cpp#include <iostream>        // header for input/output
using namespace std;       // use names like cout directly

class Greeting {           // class definition
public:
    void show() { cout << "Welcome to SBS" << endl; }
};

int main() {               // execution starts here
    Greeting g;            // object
    g.show();
    return 0;
}

• cout << (insertion operator) prints; cin >> (extraction operator) reads input.
• endl or "\n" ends a line.
• A typical program has: include files, class declarations, member function definitions, and the main function.