Unlike the current subscription-based Illustrator, version 11.0 requires a perpetual license serial number to activate.
Users often back up these files as ISO images or compressed ZIP folders to perform offline installations via a setup.exe file.
The keyword primarily refers to legacy installation files for Adobe Illustrator CS (version 11.0). Released in October 2003 , Illustrator CS was the first version to be included in the original Adobe Creative Suite. Understanding Adobe Illustrator CS (v. 11.0)
You can open legacy .ai files in modern versions, and you can save modern files back to the "Illustrator CS" format using File > Save As to ensure they can be opened by older software.
If you are working with files from this era or need to maintain compatibility: