1.1 Step-by-Step Theory

1. You write source files in .cpp and declarations in headers. Code structure often spans multiple translation units.
2. The compiler transforms each source file separately. Preprocessing, compilation, assembly, and linking are distinct stages.
3. The linker combines object files. This is where unresolved symbols and duplicate definitions surface.
4. The executable runs directly on the operating system. There is no JVM-style managed runtime layer by default.

1.2 Build Example

g++ -std=c++20 main.cpp utils.cpp -o app
./app

2.1 Code and Output

#include 
using namespace std;

int main() {
    int count = 4;
    double price = 99.5;
    bool available = true;
    cout << count << " " << price << " " << available << endl;
}

2.2 Comparison

C++ type decisions affect not only correctness but copy behavior, lifetime, and performance. This is why the language rewards precision more than convenience-driven guessing.

3.1 Example

#include 
#include 
using namespace std;

int passedCount(const vector& scores) {
    int passed = 0;
    for (int score : scores) {
        if (score >= 40) {
            ++passed;
        }
    }
    return passed;
}

3.2 Function Design Comparison

4.1 Container Example

#include 
#include 
using namespace std;

vector values = {10, 20, 30};
values.push_back(40);
cout << values.size() << endl;

4.2 Comparison

5.1 Class Example

class Account {
private:
    double balance;

public:
    explicit Account(double balance) : balance(balance) {}

    void deposit(double amount) { balance += amount; }
    double getBalance() const { return balance; }
};

5.2 Design Insight

6.1 Polymorphism Example

class Shape {
public:
    virtual double area() const = 0;
    virtual ~Shape() = default;
};

class Circle : public Shape {
    double radius;
public:
    explicit Circle(double r) : radius(r) {}
    double area() const override { return 3.14159 * radius * radius; }
};

6.2 Comparison

7.1 Template Example

template 
T maxValue(T a, T b) {
    return (a > b) ? a : b;
}

cout << maxValue(10, 20) << endl;
cout << maxValue(3.5, 2.1) << endl;

7.2 Template Thinking

8.1 Smart Pointer Example

#include 
using namespace std;

auto value = make_unique(42);
cout << *value << endl;

8.2 Ownership Comparison

RAII means resource acquisition is initialization: object lifetime controls resource lifetime. This principle applies not only to memory but also files, locks, sockets, and other managed resources.

9.1 Algorithm Example

#include 
#include 

vector values = {5, 2, 9, 1};
sort(values.begin(), values.end());
for (int value : values) {
    cout << value << " ";
}

9.2 STL Perspective

10.1 Modern Syntax Example

vector> users = {{"Asha", 82}, {"Ravi", 91}};
for (const auto& [name, score] : users) {
    cout << name << ": " << score << endl;
}

10.2 Comparison

11.1 File Example

#include 
#include 
using namespace std;

ofstream out("report.txt");
out << "C++ course completed" << endl;
out.close();

ifstream in("report.txt");
string line;
getline(in, line);
cout << line << endl;

11.2 Defensive Thinking