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As presented by Hao Wang (1954, 1957), his basic machine B is an extremely simple computational model equivalent to the Turing machine. It is "the first formulation of a Turing-machine theory in terms of computer-like models" (Minsky (1967) p. 200). With only 4 sequential instructions it is very similar to, but even simpler than, the 7 sequential instructions of the Post–Turing machine. In the same paper, Wang introduced a variety of equivalent machines, including what he called the W-machine, which is the B-machine with an "erase" instruction added to the instruction set. == Description == As defined by Wang (1954) the B-machine has at its command only 4 instructions: *(1) → : Move tape-scanning head one tape square to the right (or move tape one square left), then continue to next instruction in numerical sequence; *(2) ← : Move tape-scanning head one tape square to the left (or move tape one square right), then continue to next instruction in numerical sequence; *(3) * : In scanned tape-square print mark * then go to next instruction in numerical sequence; *(4) Cn: Conditional "transfer" (jump, branch) to instruction "n": If scanned tape-square is marked then go to instruction "n" else (if scanned square is blank) continue to next instruction in numerical sequence. A sample of a simple B-machine instruction is his example (p. 65): : 1. *, 2. →, 3. C2, 4. →, 5. ← He rewrites this as a collection of ordered pairs: : Wang's W-machine is simply the B-machine with the one additional instruction *(5) E : In scanned tape-square erase the mark * (if there is one) then go to next instruction in numerical sequence. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Wang B-machine」の詳細全文を読む スポンサード リンク
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