Calling the downcase or upcase method on a string will return the lowercase or uppercase version of the string, but the original variable won't change.

name = 'Ruby'
puts name           # Ruby
puts name.downcase  # ruby
puts name.upcase    # RUBY
puts name           # Ruby

Calling the same methods followed by an exclamation mark will both return lowercase/uppercase version of the string and will also change the content of the variable.

puts name.downcase! # ruby
puts name           # ruby

puts name.upcase!   # RUBY
puts name           # RUBY

Full example

examples/ruby/case.rb

name = 'Foo'
puts name           # Ruby
puts name.downcase  # ruby
puts name.upcase    # RUBY
puts name           # Ruby


puts name.downcase! # ruby
puts name           # ruby

puts name.upcase!   # RUBY
puts name           # RUBY

Comments

Should not the output is based on name = 'Foo'?

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Yes, it is but I'm sure that wasn't important in this case.

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For most folk not especially, we get the intent... but imagine just starting to learn programming for the first time... what you see and what you expect are different, and you could get confused.

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You did a good job. I think many people will benefit from this post.