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Preliminaries
* For the TM in question the tape upon which it operates consists of cells numbered by the integers.
* At time 0 TM begins operating and scans cell 0.
* TM operates only between time 0 and the first moment after TM halts. At t < 0 and t > halting time nothing is happening.
* Recall that any TM is specified by a description consisting of a set of quadruples that represent, in order: the state the machine is in, the symbol read, the action performed, and the new state entered.
There are just 3 types of quadruple.
1. (qi, Sj, Sk, qm) - rewrite
2. (qi, Sj, R, qm) - move right
3. (qi, Sj, L, qm) - move left