To quote the C++ standard, §3.9.1 ¶8: There are three floating point types: float, double, and long double. The type double provides at least as much precision as float, and the type long double provides at least as much precision as double. The set of values of the type float is a subset of the … Read more
Ad 1. Those types are designed to work with numbers with huge dynamic range. The long double is implemented in a native way in the x87 FPU. The 128b double I suspect would be implemented in software mode on modern x86s, as there’s no hardware to do the computations in hardware. The funny thing is … Read more
Yes — for long double, you need to use %Lf (i.e., upper-case ‘L’).
Quoting from Wikipedia: On the x86 architecture, most compilers implement long double as the 80-bit extended precision type supported by that hardware (sometimes stored as 12 or 16 bytes to maintain data structure . and Compilers may also use long double for a 128-bit quadruple precision format, which is currently implemented in software. In other … Read more