Basically, any computer language should be good. However, if you want to extend your codes (or routines) to commercial software, then the selection of "which" language may be an important factor. Typically a commercial software provides some tutorial examples (or cases), to learn how to connect or re-use a specific computing code in the commercial software. Thus it would be wiser to determine "useful" language to going forward.
1) If you want to re-use your codes in some commercial software
- Aspen Plus: FORTRAN is the most popular and best language to use
- Aspen Plus Dynamics/Aspen Custom Modeler: either FORTRAN or C is good
- HYSYS and HYSYS Dynamics: Visual Basic (VB6 or VB.Net) is good. C#.Net is also good (but examples are rare)
2) If you want to run or link with commercial software
Perhaps Excel VBA provides the best exercise. VB.Net (or C#.Net) is also good.