Naturally that tape also contains the tape of the machine being simulated. That situation parallels the one in current computers in which the memory contains both Program and Data . In the case of a computer the hardware sequentially executes each of the instructions specified by a program stored in the memory. These restrictions may be lifted later on. This program is basically the one presented in Example 4.1.1.
T signals the beginning of the actual tape.
If so proceed to execute the remaining part of the instruction. The machine halts in state h because there is no specified instruction that considers what occurs in that state.