Unit 1: C++ fundamentals

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.

cpp#include <iostream>
#include <iomanip>
using namespace std;
int main() {
    string name; int age; double fee;
    cout << "Enter name, age and fee: ";
    cin >> name >> age >> fee;                     // extraction operator
    int total = age;                                // assignment
    total += 5;                                     // compound assignment
    cout << "Name: " << name << '\n'
         << "Fee: " << fixed << setprecision(2) << fee << endl;   // insertion operator, manipulators
    return 0;
}

• getline(cin, line) reads a whole line with spaces; setw(n) sets field width.

• Constants: literal constants (25, 3.14, 'x', "SBS"), const variables (const double PI = 3.14159;), constexpr (compile-time), #define macros (C style), and enum constants.
• Variables can be declared anywhere before use; auto lets the compiler deduce the type; references (int &r = x;) are aliases.

• if: runs a block only if the condition is true.
• if-else: chooses between two blocks.
• Nested if / else-if ladder: tests several conditions in order.
• switch: selects one of many cases by the value of an integer or character expression; each case usually ends with break.

cint day = 3;
switch (day) {
    case 1: printf("Monday"); break;
    case 2: printf("Tuesday"); break;
    case 3: printf("Wednesday"); break;
    default: printf("Invalid day");
}

A loop repeats a block of statements while a condition holds.

c/* Sum of first n natural numbers */
int n = 10, sum = 0;
for (int i = 1; i <= n; i++) {
    sum += i;
}
printf("Sum = %d", sum);   /* 55 */

• break ends the loop (or switch) immediately and jumps to the statement after it.
• continue skips the rest of the current iteration and moves to the next one.

• goto: transfers control to a labelled statement — legal but discouraged because it makes programs hard to follow; occasionally used to exit deeply nested loops.