I have read it somewhere in this forum and signed to cs50x on edx but now what to do?
You get the proper link once you start working on the problem sets during the course. However, that gives you access to the cs50 preconfigured environment, not the cloud9 itself.
I suggest developing locally. You get a “real-life” experience, because you develop like you would on the job. You get to setup your folders, IDE’s, and everything exactly how you like. If you have bad internet or an occasional network high latency, you will probably not even notice it if you are coding offline.
I am using the cloud9 CS50 ide without having to use a credit card… what’s the problem?
Yes, when you haven’t used the ide for a while, it will display a notice telling you that “if only you paid for it, then …”, but it is actually waking itself up from the dead in the background, so wait for it…
However, if you have a machine, then why not set it up to be a development machine?