From the C++ Standard
The type of a floating literal is double unless explicitly specified
by a suffix. The suffixes f and F specify float, the suffixes l and L
specify long double.
It is interesting to compare with corresponding paragraph of the C Standard. In C there is used term floating constant
instead of floating literal
in C++:
4 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has type float. If suffixed by the letter l or L, it has type long double