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On this tape are symbols, which the machine can read and write, one at a time, using a tape head. Operation is fully determined by a finite set of elementary instructions such as "in state 42, if the symbol seen is 0, write a 1; if the symbol seen is 1, change into state 17; in state 17, if the symbol seen is 0, write a 1 and change to state 6 ...
tape Turing machine can be formally defined as a 7-tuple = ,,,,, , following the notation of a Turing machine: is a finite, non-empty set of tape alphabet symbols;; is the blank symbol (the only symbol allowed to occur on the tape infinitely often at any step during the computation);
A Multitrack Turing machine is a specific type of multi-tape Turing machine. In a standard n-tape Turing machine, n heads move independently along n tracks. In a n-track Turing machine, one head reads and writes on all tracks simultaneously. A tape position in an n-track Turing Machine contains n symbols from the tape alphabet.
Using letter copying presses, copies could be made up to twenty-four hours after a letter was written, though copies made within a few hours were best. A copying clerk would begin by counting the number of master letters to be written during the next few hours and by preparing the copying book. Suppose the clerk wanted to copy 20 one-page letters.
A Polygraph is a duplicating device that produces a copy of a piece of writing simultaneously with the creation of the original, using pens and ink. Patented by John Isaac Hawkins on May 17, 1803, it was most famously used by the third U.S. president, Thomas Jefferson , who acquired his first polygraph in 1804 and later suggested improvements ...
A read-only Turing machine or two-way deterministic finite-state automaton (2DFA) is class of models of computability that behave like a standard Turing machine and can move in both directions across input, except cannot write to its input tape. The machine in its bare form is equivalent to a deterministic finite automaton in computational ...
In a punched-tape system, the message is first typed onto punched tape using the code of the telegraph system—Morse code for instance. It is then, either immediately or at some later time, run through a transmission machine which sends the message to the telegraph network. Multiple messages can be sequentially recorded on the same run of tape.
The Alberti Cipher disk. The Alberti Cipher, created in 1467 by Italian architect Leon Battista Alberti, was one of the first polyalphabetic ciphers. [1] In the opening pages of his treatise De componendis cifris [] he explained how his conversation with the papal secretary Leonardo Dati about a recently developed movable type printing press led to the development of his cipher wheel.