C++ Data Types & I/O

#include <iostream>
#include <string>
using namespace std;

int main() {
    // Fundamental types (same as C + additions)
    int age = 25;
    double pi = 3.14159;
    char grade = 'A';
    bool isActive = true;       // C++ native bool
    string name = "Alice";      // C++ string (not char array!)

    // auto keyword (compiler infers type)
    auto count = 42;           // int
    auto price = 9.99;         // double
    auto greeting = "Hello"s;  // string (with s suffix)

    // cout: type-safe output (no format specifiers!)
    cout << "Name: " << name << ", Age: " << age << endl;
    cout << "Pi: " << pi << ", Active: " << boolalpha << isActive << endl;

    // cin: type-safe input
    cout << "Enter your name: ";
    getline(cin, name);  // Read full line (including spaces)

    int userAge;
    cout << "Enter age: ";
    cin >> userAge;

    // References (alias for existing variable)
    int x = 10;
    int &ref = x;   // ref IS x (not a copy, not a pointer)
    ref = 20;
    cout << "x = " << x << endl;  // 20

    // const reference (safe, no copy)
    const string &nameRef = name;  // Can read, cannot modify

    // C++ strings vs C strings
    string s1 = "Hello";
    string s2 = " World";
    string s3 = s1 + s2;       // Concatenation with +
    cout << s3.length() << endl; // 11
    cout << s3.substr(0, 5) << endl; // "Hello"

    // Range-based initialization
    int arr[] = {1, 2, 3, 4, 5};
    for (int val : arr) {  // Range-based for loop
        cout << val << " ";
    }

    return 0;
}