We must, however, always know which command is to be executed first. A programming habit that will insure consistency is to number one's commands consecutively from 1, and to list them in numerical order. That way, one may tell at a glance whether there are more than two with the same name. T programs may be represented in tables. The table is blank where no action is specified by the program.
Tables are helpful for two reasons.
First, they tell us that the program would halt if it ever came to a juncture represented by a blank on the table. Moreoever, a T program may halt in other ways, e.g. by running all its commands. Were it not for these facts, making a table for a program would infallibly tell us whether it halted. We will prove this in the second hand-out . Second, tables can help guarantee consistency.