How to implement precompiled headers into your project

Question

I understand the purpose and reasoning behind precompiled headers. However, what are the rules when implementing them? From my understanding, it goes something like this:

Answer 1

"stdafx" is just a convention. It's in no way mandatory. In a multi-project solution, I've used other setups with multiple pre-compiled headers for different parts. E.g. it may be useful to have one PCH shared by your UI projects, and another one for your database projects.

The relevant components are the X.h file listing precompilable headers, the X.cpp file that includes only X.h (and adds no code itself), and the X.pch file created by compiling X.cpp (and thus X.h) with compiler option /Yc.

When you're now compiling Y.cpp file with /Yu"X.pch", the compiler reads and discards everything up to #include "X.h". At that point it replaces its internal state with the state stored in X.pch, except for the input stream (remains Y.cpp, with the file pointer set to the next line after #include "X.h").