# SDI System Variable [GstarCAD 2022](Help%20System/GSTARCAD/2022/Index.md) → [System Variables](Help%20System/GSTARCAD/2022/System%20Variables/(System%20Variables).md) → [S](Help%20System/GSTARCAD/2022/System%20Variables/S/(S).md) **Function Description:** The SDI system variable is used to control the program running on a single file interface or multiple file interfaces. The SDI system variable can not be reset to 1 when multiple documents are already opened in the software. | | | | --- | --- | | Type | Integer | | Saved in | Registry | | Initial value | 0 | | Range | 0,1 | **System Variable Value:** **0:** opens multiple file interfaces. **1:** opens a single file interface. And you will be prompted to save the current drawing, prior to opening or creating any other drawings.