CodeSchool - learn the basics of ruby
Ruby is a programming language from Japan (available at ruby-lang.org) which is revolutionizing the web. The beauty of Ruby is found in its balance between simplicity and power.
IRB or irb is a REPL for programming in the object-oriented scripting language Ruby. The abbreviation irb comes from the fact that the filename extension for Ruby is ".rb", although interactive Ruby files do not have an extension of ".irb".
To use the IRB, access a OSX terminal, and type irb. Note that IRB was installed by default at OSX.
$try-ruby git:(master) irb
2.0.0-p247 :001 >
Ruby recognizes numbers and mathematic symbols. You could try some other math like: 4 * 10 5 - 12 40 / 4