Mapping .INI File Entries to the Registry


Under Microsoft Windows NT, Windows 2000, and Windows XP, .INI file variables are mapped into the Registry as defined in the
\HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\IniFileMapping
mapping key. The Win32 Profile application programming interface (API) functions look for a mapping by looking up the filename extension portion of the profile file. If a match is found, then the search continues under that node for the specified application name. If a match is found, then the search continues for the variable name. If the variable name is not found, the value of the (NULL) variable name is a string that points to a node in the Registry, whose value keys are the variable names. If a specific mapping is found for the variable name, then its value points to the Registry value that contains the variable value.


The Profile API calls go to the Windows server to look for an actual .INI file, and read and write its contents, only if no mapping for either the application name or filename is found. If there is a mapping for the filename but not the application name, and there is a (NULL) application name, the value of the (NULL) variable will be used as the location in the Registry of the variable, after appending the application name to it.


In the string that points to a Registry node, there are several prefixes that change the behavior of the .INI file mapping:

! - This character forces all writes to go both to the Registry and
to the .INI file on disk.

# - This character causes the Registry value to be set to the value
in the Windows 3.1 .INI file when a new user logs in for the
first time after setup.

@ - This character prevents any reads from going to the .INI file
on disk if the requested data is not found in the Registry.

USR: - This prefix stands for HKEY_CURRENT_USER, and the text after
the prefix is relative to that key.

SYS: - This prefix stands for HKEY_LOCAL_MACHINE\Software, and the
text after the prefix is relative to that key.