FORTRAN

I used plenty of Fortran back in college, and it's not too difficult. Granted, FORTRAN 90 has a lot of improvement over FORTRAN 77. Just remember that it's a much more primitive language, that is primarily used for math and engineering. You won't find much memory management, or pointers, or any object oriented concepts. It's all strictly procedural programming. In practice, you typically use the Implicit statement to declare all variables beginning with the letters i through n, as integers, and the rest as real or double.

Once I learned C++, I couldn't stand Fortran, so good luck.

( For modeling dynamic systems, I'd recommend using Matlab. )

Jam it back in, in the dark.