Variables and Types

C++'s fundamental types include int, double, bool, and char. Every variable has a type, and that type is fixed once declared. Note that cout prints a bool as 0 or 1, not the words true/false, unless you explicitly ask for the word form.

#include <iostream>
using namespace std;

int main() {
    int age = 30;
    double price = 19.99;
    bool isStudent = false;
    char grade = 'A';

    cout << age << " " << price << " " << isStudent << " " << grade << endl;
    return 0;
}

30 19.99 0 A

auto and const

auto lets the compiler infer a variable's type from its initializer — useful when the type is obvious or verbose, though it still produces a fixed, fully static type, not a dynamic one. const marks a variable as unmodifiable after initialization; the compiler enforces this at compile time.

#include <iostream>
using namespace std;

int main() {
    auto count = 42; // inferred as int
    auto pi = 3.14159; // inferred as double
    const int maxUsers = 100;
    cout << count << " " << pi << " " << maxUsers << endl;
    return 0;
}

42 3.14159 100

Next: references and pointers — two different ways to refer to a value without copying it, and the genuinely C++-specific distinction between them.