I successfully accessed the .mat and .str file via the mat2ascii and str2ascii utility, but I cannot access the electric field data in the .rhs file. The only information I found is https://2021.help.altair.com/2021/feko/topics/feko/user_guide/appendix/file_rhs_read_feko_c.htm ,but the explanations are very brief. How do you access the data in the .rhs file in detail? From reading related posts I guess it involves Fortran, but I'm not familiar with Fortran at all. Perhaps I could get some advice here.