What software is required to make a simple program control an arduino?
Eg. I have an elevator and want to select which floor it goes to with a press of a button on a PC application
The PC must send serial data to the Arduino.
All kinds of software exists to do that. Look into "Processing" as one example.
Any PC programming language or application program that knows how to talk to the PC com ports can work with an attached arduino board using serial communications.
I wrote a demo program in Python that communicates with an Arduino in this Thread.
...R