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This option instructs the compiler to create a precompiled header (.PCH) file that represents the state of compilation at a certain point. (To find this option in the development environment, click Settings on the Project menu. Then click the C/C++ tab, and click Precompiled Headers in the Category box.)
| Command Line | Project Settings | Description |
| /Yc | Create Precompiled Header File | The compiler compiles all code up to the end of the base source file, or to the point in the base file where #pragma hdrstop occurs. |
| /Ycfilename | Through Header | The compiler compiles all code up to and including the .H file specified in the Through Header text box (filename). |
The precompiled code is saved in a file with a name created from the base name of the file specified with the /Yc option and a .PCH extension. You can also use the /Fp option to specify a name for the precompiled header file.
If you use /Ycfilename (Through Header), the compiler compiles all code up to and including the specified file for subsequent use with the /Yu option.
Note If the options /Ycfilename and /Yufilename occur on the same command line and both reference, or imply, the same file name, /Ycfilename, takes precedence. This feature simplifies the writing of makefiles.
Consider the following code:
#include <afxwin.h> // Include header for class library
#include "resource.h" // Include resource definitions
#include "myapp.h" // Include information specific to this app
...When this code is compiled with the command
CL /YcMYAPP.H PROG.CPPthe compiler saves all the preprocessing for AFXWIN.H, RESOURCE.H, and MYAPP.H in a precompiled header file called MYAPP.PCH.
See Also Creating Precompiled Header Files