In the first two articles in this series, we have become acquainted with the hardware and software of the Lego Robotics Invention System. Here, in the third article, we see how the RCX block can be programmed using Microsoft Visual BASIC or another object-oriented programming language. Such a language puts us a lot closer to the hardware, so that we can better determine what the robot does.In the previous articles, we have seen that the Robotics Invention System (RIS) is a very compact package, in regard to both the hardware and the software. The software is very user-friendly, and it should be perfect for the beginner in robotics and programming. However, if you really want to see what is happening inside the RCX block, you will soon feel the need for other software packages. In this article, we assume that you have already worked with Visual BASIC.