QuestaSim 10.7c is a legacy version of the Siemens (formerly Mentor Graphics) high-performance HDL simulation environment. Because it is a professional, licensed EDA (Electronic Design Automation) tool, there is no official "public" download link available for general users. Official Download Method
Recommendation: Based on my experience, I recommend Questasim 10.7c to: questasim 10.7c download
Once you’ve downloaded the questasim-10.7c.exe (Windows) or the .run file (Linux): QuestaSim 10
2. The Academic Route If you are a student or researcher, do not buy a license outright—most universities have agreements with Siemens. licensed EDA (Electronic Design Automation) tool