Important note: Class names in ruby have to start with a capital letter.

gistfile1.txt

Important note:  Class names in ruby have to start with a capital letter.  So in the "Ruby in 100 minutes" exercise, the code example has  "class Sample"  -- not "class sample" !   If you are getting an error like:

NameError: undefined local variable or method `sample_hello' for main:Object
        from (irb):1
        from C:/RailsInstaller/Ruby1.9.3/bin/irb:12:in `<main>'

then edit your ruby source file   my_program.rb  and make sure you have a capital letter 'S' in Sample
     class Sample