In the computer era, punctuation characters were recycled for use in programming languages and URLs. Due to its use in email and Twitter handles, the at sign (@) have gone from an obscure character mostly used by sellers of bulk commodities (10 pounds @$2.00 per pound), to a very common character in common use for both technical routing and an abbreviation for "at". The tilde (~), in moveable type only used in combination with vowels, for mechanical reasons ended up as a separate key on mechanical typewriters, and like @ it has been put to completely new uses.