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
DOT (graph description language) DOT (graph description language) DOT is a graph description language. DOT graphs are typically files with the file extension "gv" or "dot". The extension "gv" is preferred to avoid confusion with the extension "dot" used by early (pre-2007) versions of Microsoft Word. Various programs can process DOT files. Some, such as "dot", "neato", "twopi", "circo", "fdp", and "sfdp", can read a DOT file and render it in graphical form. Others, such as "gvpr", "gc", "acyclic", "ccomps", "sccmap", and "tred", read DOT files and perform calculations on the represented graph. Finally, others, such as "lefty", "dotty", and "grappa", provide an interactive