Error when input cd C:

So I'm reading "Ruby Wizardry" by Eric Weinstein and I'm up to the script part and when I input: cd C:\Users\Ender\ruby, Ruby responds with "SyntaxError: <irb>:7: syntax error, unexpected $undefined cd C:\Users\Ender\ruby" What's the syntax error? I input everything as the book said. I have Ruby 2.0.0-p645. Can anyone help, I would appreciate it! BTW, I have .rb files on standby ready for reading and the file exists. The proper command is Dir.chdir DIRECTORY.