1. input
print "What's your first name?" first_name = gets.chomp
chomp will delete "\n" from the string
http://www.ruby-doc.org/docs/Tutorial/part_02/user_input.html
2. output
with format #{variable_name}
first_name = "Kevin" puts "Your name is #{first_name}!"
city = gets.chomp puts "The city is " + city
3. exclaimation mark !
make value contain in the variable itself
state.upcase!
same as
state=state.upcase
