Chorded keyboard (a writing system for the blind) uses either 6 or 8 tactile 'points' from which all letters and numbers are formed. When Louis Braille invented it, it was produced with a needle holing successively all needed points in a cardboard sheet. In 1892, Frank Haven Hall, superintendent of the Illinois Institute for the Education of the Blind, created the Hall Braille Writer, which was like a typewriter with 6 keys, one for each dot in a braille cell. The Perkins Brailler, first manufactured in 1951, uses a 6-key chord keyboard (plus a spacebar) to produce braille output, and has been
Writing system are able to represent all that may be expressed in the spoken language, while a "partial" writing system is limited in what it can convey. Writing systems can be independent from languages, one can have multiple writing systems for a language, e.g., Hindi and Urdu; and one can also have one writing system for multiple languages, e.g., the Arabic script. Chinese characters were also borrowed by variant countries as their early writing systems, e.g., the early writing systems of Vietnamese language until the beginning of the 20th century. To represent a conceptual system, one uses one or more languages, e.g.,