C++ Tutorial · C++ Basics · Lesson 4 of 21

C++ Variables and Data Types

Fundamental types, auto, const, constexpr and initialisation.

Fundamental types

Type	Example
`int`, `long long`	`42`, `9'000'000'000LL`
`double`, `float`	`3.14`, `2.5f`
`bool`	`true`
`char`	`'A'`
`std::string`	`"text"` (from `<string>`)

Example 1

#include <iostream>
#include <limits>
#include <string>

int main() {
    int age{36};
    double height = 1.68;
    char grade = 'A';
    bool active = true;
    std::string name = "Ada";
    auto population = 8'100'000LL;      // long long
    const double pi = 3.14159;
    constexpr int squares = 12 * 12;    // computed at compile time
    std::cout << name << ' ' << age << ' ' << height << ' ' << grade << ' ' << active << '\n';
    std::cout << population << ' ' << pi << ' ' << squares << '\n';
    std::cout << 7 / 2 << ' ' << 7 / 2.0 << ' ' << static_cast<double>(7) / 2 << '\n';
    std::cout << sizeof(int) << ' ' << sizeof(double) << ' ' << std::numeric_limits<int>::max() << '\n';
}

Output

Ada 36 1.68 A 1
8100000 3.14159 144
3 3.5 3.5
4 8 2147483647

Run this on your computer — see “Get Started” for setup.

Brace initialisation int x{5}; prevents narrowing conversions.
auto deduces the type from the initialiser.
const values can't change; constexpr values are computed at compile time.

Type conversion

Use static_cast<T>(value) for explicit conversions — it's searchable and safer than C-style casts.

Test yourself

Which keyword computes a constant at compile time?

const
constexpr
static
final

Show answer

Answer: constexpr