A number of typographical conventions originate from the widespread use of the typewriter, based on the characteristics and limitations of the typewriter itself. For example, the QWERTY keyboard typewriter did not include keys for the en dash and the em dash. To overcome this limitation, users typically typed more than one adjacent hyphen to approximate these symbols. This typewriter convention is still sometimes used today, even though modern computer word processing applications can input the correct en and em dashes for each font type. Double hyphens are also standard in Western comics lettering despite historically being done by hand.