Ruby Numbers

Least significant bit

The least significant bit is sometimes called the bottom bit. If it is 0 (zero), it means it is an even number. If it is 1 (one), it means it is an odd number. The odds are reserved to represent small integers (which used to be Fixnum in older versions of Ruby).

Integer, Bignum and Fixnum

While internally Integer up to 62 bit are stored as immediate values the distinction between Fixnum and Bignum is not longer exposed to the user. In the old days we had the classes Fixnum and Bignum as subclasses of Integer, but in modern Ruby 5.class will return Integer, for example.