Overprinting was intended to work by putting a backspace code between the codes for letter and diacritic. Instead a single key was changed to a tilde dead key and ⟨~⟩ was born as a distinct grapheme.ĪSCII incorporated many of the overprinting lower-case diacritics from typewriters, including tilde. Whereas it was just about possible to find one low-use key to sacrifice for Spanish, to find two sacrificial keys for Portuguese was impractical.
Portuguese, however, has two: ã Ã and õ Õ. Both were precomposed as distinct graphemes and assigned to a single typebar, which sacrificed a key that was felt to be less important, usually the 1⁄ 4 1⁄ 2 key. In modern Spanish, the tilde accent is needed only for the characters ñ and Ñ. Spanish and Portuguese uniquely use the tilde diacritic.
On others, however, the typebar had two different diacritics so that users could only add accents to lower-case letters without manual intervention or other adjustment.įor most Western European languages, the only diacritics used are acute ( ´), grave ( `, circumflex ( ˆ) and diaeresis (or umlaut, ¨): early typewriters for the European market included these as dead keys.
To add a diacritic to a capital letter on some typewriters, the upper-case version of the accent could be produced using ⇧ Shift plus the diacritic key. Since the diacritic key – a 'dead key' – had not moved the paper on, the letter was printed under the previously-printed accent. To achieve an accented letter, the typist first typed the desired diacritic, then typed the letter to be accented. On typewriters designed for languages that routinely use diacritics (accent marks), a dead key mechanism was provided: a mark is made when a dead key is typed but, unlike normal keys, the paper carriage does not move on. This symbol did not exist independently as a type or hot-lead printing character. The incorporation of the tilde into ASCII is a direct result of its appearance as a distinct character on Portuguese mechanical typewriters in the late nineteenth century. In lexicography, the latter kind of tilde and the swung dash, ⁓, are used in dictionaries to indicate the omission of the entry word. These are encoded in Unicode with many precomposed characters as well as individually at U+0303 ◌̃ COMBINING TILDE and U+007E ~ TILDE (as a spacing character), and there are additional similar characters for different roles. The tilde has since been applied to a number of other uses as a diacritic mark or a character in its own right. Medieval European charters written in Latin are largely made up of such abbreviated words with suspension marks and other abbreviations only uncommon words were given in full. This saved on the expense of the scribe's labour and the cost of vellum and ink. Such a mark could denote the omission of one letter or several letters. Thus, the commonly used words Anno Domini were frequently abbreviated to A o Dñi, with an elevated terminal with a suspension mark placed over the "n". It was originally written over an omitted letter or several letters as a scribal abbreviation, or "mark of suspension" and "mark of contraction", shown as a straight line when used with capitals.