Many of the source code examples that come with this book are documented with comments that are ignored by the Ruby interpreter. You can place a comment after the hash mark (#). The text on a line following this character is all treated as a comment:

# this is a comment
puts( "hello" ) # this is also a comment

If you want to comment out multiple lines of text, you can place =begin at the start and =end at the end (both =begin and =end must be flush with the left margin):

=begin
 This is a
 multiline
 comment
=end