Ruby Hashes

A hash maps keys to values. The literal { "Ada" => 91 } uses => between each key and value, and scores["Linus"] = 79 adds a new pair. Ruby hashes remember the order in which keys were added.

scores = { "Ada" => 91, "Grace" => 88 }
scores["Linus"] = 79
scores.each do |name, score|
  puts "#{name}: #{score}"
end
puts scores.size