This appendix provides an overview of programming techniques for controlling the VectorStar Series VNAs with older legacy software. Best practices recommend using the techniques and software described in Appendix A, B, and C for new development. This appendix describes using the NI-VISA driver and C# over GPIB, TCP/IP (using VXI-11), and USB. Programming using TCP/IP Sockets requires some special handling and is not discussed in this document.