Using Dirids

Many of the directories that appear in INF files can be expressed using directory identifiers (dirids), which are numbers that identify specific directories. Dirids whose values are from -1 through 32767 are reserved for system use. To create dirids with user-defined values from 32768 through 65534, or 65536 and up, use the SetupSetDirectoryId function (described in the Platform SDK documentation). Note that for compatibility with Microsoft® Windows® 9x/Me, dirid 65535 is considered to be synonymous with dirid -1, although the latter (dirid -1) is preferred.

If you intend to use dirids in your INF file, consider the following two guidelines:

When the syntax for an INF file entry explicitly specifies a dirid value (the INF DestinationDirs section, for example), express that value as a number. Here is an example:
```
[DestinationDirs]
DefaultDestDir = 11  ;  \system32 directory on NT-based systems
```
When the syntax for an INF file entry specifies a file path, you can use a system-supplied string substitution to represent part or all of this path. This substitution has the following form:
%dirid%
This form consists of a percent (%) character, followed by the dirid for the directory you want to specify, followed by another percent (%) character. A terminating backslash (\) character separates this expression from a following filename or additional directories in the path.
The following example demonstrates this syntax.
```
[aic78xx_Service_Inst]
ServiceBinary = %12%\aic78xx.sys
```
When fully expanded, the path shown in the previous example becomes c:\windows\system32\drivers\aic78xx.sys (assuming that Windows was installed in the c:\windows directory). Note that the string substitution, or %dirid% form, can be used anywhere a string is expected, with the exception of the INF Strings section of the INF file.
The two following examples show how string substitution should not be used.
```
[DestinationDirs]
DefaultDestDir = %11%  ; Error! - number expected

[aic78xx_Service_Inst]
ServiceBinary = 12\aic78xx.sys  ; Error! - unknown directory name
```
In the first example, the syntax for the DefaultDestDir entry requires its value to be a number, but the %11% expression expands to a string. In the second example, the INF writer apparently intended to set the value for the ServiceBinary entry to a file in the directory containing drivers (see the following table for more information). The error occurs because Setup looks for the specified file in a directory named "12", which probably does not exist on the machine.

The following table shows several commonly-used dirids, and the directories they represent. The values most commonly specified by device INF files and driver INF files are listed toward the top of the table.

Value	Destination Directory
01	SourceDrive:\pathname (the directory from which the INF file was installed)
10	Windows directory This is equivalent to %windir%.
11	System directory This is equivalent to %windir%\system32 for NT-based systems, and to %windir%\system for Windows 9x/Me.
12	Drivers directory This is equivalent to %windir%\system32\drivers for NT-based platforms, and to %windir%\system\IoSubsys on Windows 9x/Me platforms.
17	INF file directory
18	Help directory
20	Fonts directory
21	Viewers directory
23	Color directory (ICM) (not used for installing printer drivers)
24	Root directory of the system disk. This is the root directory of the disk on which Windows files are installed. For example, if dirid 10 is "C:\winnt", then dirid 24 is "C:\".
25	Shared directory
30	Root directory of the boot disk, also known as "ARC system partition," for NT-based systems. (This might or might not be the same directory as the one represented by dirid 24.)
50	System directory for NT-based operating systems This is equivalent to %windir%\system (NT-based systems only).
51	Spool directory (not used for installing printer drivers – see Printer Dirids)
52	Spool drivers directory (not used for installing printer drivers)
53	User profile directory
54	Directory where ntldr.exe and osloader.exe are located (NT-based systems only)
55	Print processors directory (not used for installing printer drivers)
-1	Absolute path

Dirid values from 16384 through 32767 are reserved for special shell folders. The following table shows dirid values for these folders:

Value	Shell Special Folder
16406	All Users\Start Menu
16407	All Users\Start Menu\Programs
16408	All Users\Start Menu\Programs\Startup
16409	All Users\Desktop
16415	All Users\Favorites
16419	All Users\Application Data
16422	Program Files
16427	Program Files\Common
16429	All Users\Templates
16430	All Users\Documents

Besides the values listed in this table that are defined in setupapi.h, you can use any of the CSIDL_Xxx values defined in shlobj.h. To define a dirid value for a folder not listed in this table, add 16384 (0x4000) to the CSIDL_Xxx value. For more information on CSIDL_Xxx values, see the Platform SDK documentation.