I started learning Ruby two days ago. I checked out the source code and it seemed to be all in C. I couldn't find why it hasn't been converted to Ruby (performance reasons?), so asking here.
There are many Ruby implementations, a very popular one is Rubinius which is implemented in Ruby <a href="http://rubini.us/" rel="nofollow">http://rubini.us/</a><p>The MRI or Matz's Ruby Interpreter (also called CRuby) is the reference implementation (Though RubySpec started by the Rubinius project has become the standard). Other implementations are very popular, such as JRuby that allows for running Ruby in the JVM.