Hello, I am in need of some assistance with trying to get my fist ruby program to run. I am reading the book "Learn to program by chris pine" and he seems to be using a different DOS version them me. I think hes on a mac or using an XP version. His says version is "Microsoft Windows XP [Version 5.1.2600] 1985-2001 Microsoft Corp. I am running windows 7, my version is 6.1.7601 2009. Anyways the commands that he is telling me are not adding up. I tried the ruby -v to see if ruby was installed and the error I got was that it was not recognized in dos as an internal or external command? When I tried to go to the programs folder dos says it can't find it. When I saved my calc.rb file and tried to run it with ruby calc.rb DOS didn't recognize the command ether. I was in the correct directory. What could be the issue?