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In addition, the Turing machine can also have a reject state to make rejection more explicit. In that case there are three possibilities: accepting, rejecting, and running forever. Another possibility is to regard the final values on the tape as the output. However, if the only output is the final state the machine ends up in (or never halting), the machine can still effectively output a longer string by taking in an integer that tells it which bit of the string to output.
In addition, the Turing machine can also have a reject state to make rejection more explicit. In that case there are three possibilities: accepting, rejecting, and running forever. Another possibility is to regard the final values on the tape as the output. However, if the only output is the final state the machine ends up in (or never halting), the machine can still effectively output a longer string by taking in an integer that tells it which bit of the string to output.
此外，图灵机还可以有一个拒绝状态，以使拒绝更加明确。在这种情况下，存在三种可能：接受、拒绝和一直运行。另一种可能是将磁带上的最终值视为输出。但是，如果唯一的输出是机器最终进入的状态（或永不停止），则机器仍可以通过接受一个整数来有效地输出一个较长的字符串，该整数告诉它要输出字符串的哪一位。
A relatively uncommon variant allows "no shift", say N, as a third element of the set of directions <math>\{L,R\}</math>.
A relatively uncommon variant allows "no shift", say N, as a third element of the set of directions <math>\{L,R\}</math>.