Bring /Fi up to snuff

Colin Robertson · Colin Robertson · commit b56af56378b2 · 2020-08-13T14:14:01.000-07:00
diff --git a/docs/build/reference/fi-preprocess-output-file-name.md b/docs/build/reference/fi-preprocess-output-file-name.md
@@ -13,27 +13,49 @@ Specifies the name of the output file to which the [`/P` (Preprocess to a File)]
 
 > **`/Fi`**_`pathname`_
 
-#### Parameters
+### Parameters
 
 *`pathname`*\
-The name and path of the output file produced by the **`/P`** compiler option.
+The relative or absolute path and filename of the output file produced by the **`/P`** compiler option. Or, the directory path for the *`.i`* output files when more than one input file is specified. Don't put a space between the **`/Fi`** option and *`pathname`*.
 
 ## Remarks
 
-Use the **`/Fi`** compiler option in combination with the **`/P`** compiler option.
+Use the **`/Fi`** compiler option in combination with the **`/P`** compiler option. If **`/P`** isn't specified, **`/Fi`** causes command line warning D9007.
 
-If you specify only a path for the *`pathname`* parameter, the base name of the source file is used as the base name of the preprocessed output file. The *`pathname`* parameter doesn't require a particular file name extension. However, an extension of ".i" is used if you don't specify a file name extension.
+If you specify only a directory path (a path that ends in a backslash **`\`**) for the *`pathname`* parameter, the base name of the source file is used as the base name of the preprocessed output file. The *`pathname`* parameter doesn't require a particular file name extension. However, an extension of ".i" is used if you don't specify a file name extension.
 
-## Example
+### Example
 
-The following command line preprocesses *`PROGRAM.cpp`*, preserves comments, adds [`#line`](../../preprocessor/hash-line-directive-c-cpp.md) directives, and writes the result to the *`MYPROCESS.i`* file.
+The following command line preprocesses *`PROGRAM.cpp`*, preserves comments, adds [`#line`](../../preprocessor/hash-line-directive-c-cpp.md) directives, and writes the result to the *`MYPROCESS.i`* file:
 
 ```cmd
 CL /P /FiMYPROCESS.I PROGRAM.CPP
 ```
 
+This command line preprocesses *`main.cpp`* and *`helper.cpp`* into *`main.i`* and *`helper.i`* in a subdirectory named *`preprocessed`*:
+
+```cmd
+CL /P /Fi".\\preprocessed\\" main.cpp helper.cpp
+```
+
+### To set this compiler option in the Visual Studio development environment
+
+1. Open the source file or the project's **Property Pages** dialog box. For details, see [Set C++ compiler and build properties in Visual Studio](../working-with-project-properties.md).
+
+1. Select the **Configuration Properties** > **C/C++** > **Preprocessor** property page.
+
+1. Set the **Preprocess to a File** property to **Yes**.
+
+1. Select the **Configuration Properties** > **C/C++** > **Command Line** property page.
+
+1. Enter the **`/Fi`** compiler option and *`pathname`* in the **Additional Options** box. Only specify a directory path, not a filename, when setting this property for a project.
+
+### To set this compiler option programmatically
+
+- See <xref:Microsoft.VisualStudio.VCProjectEngine.VCCLCompilerTool.AdditionalOptions%2A>.
+
 ## See also
 
-[MSVC Compiler Options](compiler-options.md)<br/>
-[/P (Preprocess to a File)](p-preprocess-to-a-file.md)<br/>
-[Specifying the Pathname](specifying-the-pathname.md)
+[MSVC compiler options](compiler-options.md)<br/>
+[`/P` (Preprocess to a file)](p-preprocess-to-a-file.md)<br/>
+[Specifying the pathname](specifying-the-pathname.md)
