As you saw in the previous task, float's precision (7 decimal digits) is not always enough.
But C++ has a solution: double.
With a precision of 15 decimal digits, it is much more accurate than float.
The syntax of using double is the same as always:

Note

By default, cout prints floating-point numbers with a precision of 6 significant digits.
That way, you won't see a difference between float and double.
To set a larger precision, you can use cout << setprecision(15); (this will set the precision to 15 significant digits).
However, you must include the iomanip library using #include<iomanip> in your program.

How is better precision achieved in double?
It just takes up more memory.
A float type takes up 4 bytes, and a double takes up 8 bytes of memory.

There also is a long double type.
Its size ranges from 8 bytes (just like a double) to 16 bytes.
You can check the size of the long double on your system by using the following code:

Additionally, you should add L to a value you are assigning (otherwise, the value will be assigned with the precision of double). Look at the example:

Here is a little summary:

In the previous chapter, we converted a distance in kilometers to miles.
Let's see how precise those calculations were.

Here is an example of using double in the task from the previous chapter:

Note

If you got zeros in the output, make sure you assigned the values exactly like shown above (1/3., 1/3.L).
We will discuss the reasons for this behavior in the Arithmetic Operations chapter.