`-`~~A TuringMachine is an abstract representation of ~~
a ~~computing device. It consists ~~
of a ~~read~~
/~~write head that scans a (possibly infinite) one-dimensional (bi-directional) tape divided into squares, each of which is inscribed with a 0 or 1~~
. ~~Computation begins with the machine, in a given "state", scanning a square~~
. ~~It erases what it finds there, prints a 0 or 1, moves to an adjacent square, and goes into a new state. This behavior is completely determined by three parameters: (1) the state the ~~
machine ~~is in, (2) the number on the square it is scanning, and (3) a table of instructions~~
. ~~The table of instructions specifies, for each state and binary input, what the machine should write, which direction it should move in, and which state it should go into. (E.g., "If in State 1 scanning a : print 1, move left, and go into State 3".) The table can list only finitely many states, each of which becomes implicitly defined by the role it plays in the table of instructions. These states ~~
are ~~often referred to as the "functional states" of the machine~~
.

`+`See [
a definition
of a turing machine | http:
//plato
.stanford
.edu/entries/turing-
machine/]
. [TuringMachine]s
are named after their inventor AlanTuring
.

`-`~~A Turing machine, therefore, is more like ~~
a ~~computer program ~~
(~~software) than a computer (hardware~~
). ~~Any given Turing ~~
machine ~~can be realized or implemented on an infinite number of different physical computing devices~~
. ~~Computer scientists and logicians have shown that Turing machines -- given enough time and tape -- can compute any function that any conventional digital computers can compute~~
. ~~Also, a �probabilistic automaton� can be defined as a Turing machine in which the transition from input and state to output and state takes place with a certain probability (E~~
.~~g~~
. ~~"If in State 1 scanning a : (a) there is a 60% probability that the machine will print 1~~
, ~~move left, and go into State 3, and (b) there is a 40% probability that the machine will print , move left, and go into State 2".) ~~

`-`~~ ~~

`-`
[~~TuringMachine~~
]~~s are named after their inventor AlanTuring~~
.~~ ~~

`-`~~ ~~

`-`~~[~~
http://~~plato~~
.~~stanford.edu~~
/~~entries~~
/turing~~-machine/~~
]~~ ~~

`-`~~ ~~

`-`~~Some neat? implementations of ~~
a ~~TuringMachine are: ~~

`-`~~ ~~

`-`~~SendmailTuringMachine ~~

`-`~~EximTuringMachine ~~

`-`~~ ~~

`-`~~A mind-boggling implementation of a Turing ~~
machine ~~is: ~~

`-`~~ ~~

`-`~~Paul Rendell's [Turing Machine ~~
implemented in Conway's Game of Life|http://~~www~~
.~~rendell~~
.~~uk~~
.~~co~~
/gol/tm.htm]

`+`Creative abuse of various environments not meant to implement [TuringMachine]s with has resulted in
a sendmail
(8
) [sendmail
.cf turing
machine | http://www
.hopf
.demon
.co
.uk/demon/turing.txt]
, an
[Exim
] [exim
.conf turing machine |
http://dotat
.at
/writing
/exim-
turing.conf
] and even
a [turing
machine implemented in Conway's Game of Life | http://rendell
.server
.org
.uk
/gol/tm.htm].