Floating-point Numbers

Numbers with a decimal fraction are called floating-point numbers. They are used to model real numbers from mathematics. C++ has three different floating-point types: float, double, and long double.

Floating-point literals in C++ are written in two ways:

Using fixed-point notation (2.0). The value is stored as a double.
Using scientific or exponential notation. For instance, you can write (2.9979E+8 to represent the speed of light, instead of writing it as 299790000.) The exponent can be positive (for large numbers) or negative (for very small numbers), and you can use an uppercase or lowercase "E".

You can change the storage of your literals by appending an F for type float and an L for a type long double.

Here are some examples of floating-point literals:

auto a = 3.14159;       // fixed notation, type double
auto b = 2.997E8;       // scientific notation, type double
auto c = 299'792'458.L; // fixed notation, type long double
auto d = 3.5F;          // fixed notation, type float

Generally, use double, not float or long double.