Immediate Value
object
reference
variable
ruby
The one in ((variable|Variable)) that not ((reference|Reference))
but actual value is stored.
Only '((|Fixnum|))' and ((|nil|))/((|true|))/((|false|)) are
immediate values in present ((Ruby)).
However, there's no law against another ((Ruby))
which ((|Fixnum|)) is not immediate value, and also you can regard
the all values on the model as a ((reference|Reference))
to the ((object|Object)).