obtain sql server instalation folder code example

Example: how to find sql server installation folder

declare @rc int, @dir nvarchar(4000) 

exec @rc = master.dbo.xp_instance_regread
      N'HKEY_LOCAL_MACHINE',
      N'Software\Microsoft\MSSQLServer\Setup',
      N'SQLPath', 
      @dir output, 'no_output'
select @dir AS InstallationDirectory