Dasher is an

input method An input method (or input method editor, commonly abbreviated IME) is an operating system component or program that enables users to generate characters not natively available on their input devices by using sequences of characters (or mouse o ...

and

computer accessibility Computer accessibility (also known as accessible computing) refers to the accessibility of a computer system to all people, regardless of disability type or severity of impairment. The term ''accessibility'' is most often used in reference to spe ...

tool which enables users to compose text without using a

keyboard Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Mu ...

, by entering text on a screen with a

pointing device A pointing device is a human interface device that allows a user to input spatial (i.e., continuous and multi-dimensional) data to a computer. CAD systems and graphical user interfaces (GUI) allow the user to control and provide data to ...

such as a

mouse A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

touch screen A touchscreen or touch screen is the assembly of both an input ('touch panel') and output ('display') device. The touch panel is normally layered on the top of an electronic visual display of an information processing system. The display is ofte ...

, or mice operated by the foot or head. Such instruments could serve as prosthetic devices for disabled people who cannot use standard keyboards, or where the use of one is impractical. Dasher is

free and open-source software Free and open-source software (FOSS) is a term used to refer to groups of software consisting of both free software and open-source software where anyone is freely licensed to use, copy, study, and change the software in any way, and the source ...

, subject to the requirements of the

GNU General Public License The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general ...

(GPL), version 2. Dasher is available for operating systems with

GTK+ GTK (formerly GIMP ToolKit and GTK+) is a free and open-source cross-platform widget toolkit for creating graphical user interfaces (GUIs). It is licensed under the terms of the GNU Lesser General Public License, allowing both free and prop ...

support, i.e.

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, whi ...

, BSDs and other

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

including

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and la ...

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...

Pocket PC A Pocket PC (P/PC, PPC) is a class of personal digital assistant (PDA) that runs the Windows Mobile or Windows Embedded Compact operating system that has some of the abilities of modern desktop PCs. The name was introduced by Microsoft in 200 ...

, iOS and Android. Dasher was invented by David J. C. MacKay and developed by David Ward and other members of MacKay's Cambridge research group. The Dasher project is supported by the Gatsby Charitable Foundation and by the EU aegis-project.

Design

For whatever the writer intends to write, they select a letter from ones displayed on a screen by using a pointer, whereupon the system uses a

probabilistic Probability is the branch of mathematics concerning numerical descriptions of how likely an event is to occur, or how likely it is that a proposition is true. The probability of an event is a number between 0 and 1, where, roughly speaking, ...

predictive model to anticipate the likely character combinations for the next piece of text, and accord these higher priority by displaying them more prominently than less likely letter combinations. This saves the user effort and time as they proceed to choose the next letter from those offered. The process of composing text in this way has been likened to an

arcade game An arcade game or coin-op game is a coin-operated entertainment machine typically installed in public businesses such as restaurants, bars and amusement arcades. Most arcade games are presented as primarily games of skill and include arcade vi ...

, as users zoom through characters that fly across the screen and select them in order to compose text. The system learns from experience which letter combinations are the most popular, and changes its display protocol over time to reflect this.

Features

The Dasher package contains various architecture-independent data files: * alphabet descriptions for over 150 languages * letter colours settings * training files in all supported languages

References

External links

* {{Official website, www.inference.phy.cam.ac.uk/dasher/ User interfaces User interface techniques Pointing-device text input Disability software Free software programmed in C Free software programmed in C++ Free software programmed in Java (programming language) GNOME Accessibility Cross-platform free software Free and open-source Android software