C++ Data Types

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

int main() {
    // Basic types
    int age = 25;
    double pi = 3.14159;
    float temp = 36.6f;
    char grade = 'A';
    bool isActive = true;
    string name = "Alice";     // C++ string (not char array!)

    // Auto type deduction (C++11)
    auto x = 42;         // int
    auto y = 3.14;       // double
    auto msg = "hello"s; // string (with s suffix)

    // Constants
    const int MAX_SIZE = 100;
    // MAX_SIZE = 200;  // Error! Can't change a const

    cout << name << " is " << age << " years old" << endl;
    cout << "Active: " << boolalpha << isActive << endl;
    return 0;
}

Type Casting

// C-style cast
int a = (int)3.14;  // 3

// C++ style casts (preferred)
double d = 3.14;
int b = static_cast<int>(d);  // 3

// String to number
string numStr = "42";
int num = stoi(numStr);     // String to int
double dbl = stod("3.14"); // String to double

// Number to string
string s = to_string(42);  // "42"

References

int original = 10;
int &ref = original;  // ref IS original

ref = 20;
cout << original;  // 20 (changed through reference!)

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