This variable contains the alias of the primary installation folder. The primary installation folder is used to determine available and required disk space on the primary volume, and is registered as the installation folder in the Product uninstaller information.
Tip: On the Files and folders project page, the primary folder is shown in red: or
You can refer to this variable as <PRIMARYFOLDER>. Because the variable contains the alias of the actual primary folder, you can retrieve the primary folder path (as opposed to the primary folder alias) by using double indirection: <<PRIMARYFOLDER>>. Do not change its value directly; instead, go to the Files and folders project page, right-click on the desired primary folder, and choose the Set as Primary Folder command from the folder's context menu.
See also the topic About INSTALLDIR and PRIMARYFOLDER.