Where to get software to make a screen cast

First of all, you might ask what is a screen cast? Well a screen cast is a video of your computer screen. Below is an example of what a screen cast is.  

 

Screen casts are very useful in teaching how do things on a computer despite the long distance. You can walk others through the steps of a task and record your own voice as you teach.  

There is software that you can buy to make a screen cast, but you can also download the CamStudio for free. It's an open source code software, and Teng Li , one of the moderators of iMechanica, uses it to make the videos that he posts in iMechanica.