Read those three pages and after you read answer my question. you can answer it by give a prove or a java program.

Question:

Show that there are 21 reachable states and that a state a state of type (4,4,......) is not among those 21 ?

1.7 Synchronization by Shared Variables h ea is to let them share a certain number of variables. Even if, from a theoreti point of view, it is possible to present the shared variables using a syncht nized product, their practical interest is such that we prefer to introdte Another way to have components of a system communicate wit 0- them explicitly. We saw earlier how variables could be "added" to auto It then is natural to allow one (or several) variable(s) to be shared by several automata if turn=A, printA turn := B Fig. 1.16. The user A Consider once again the case of the two users A et B who share a printer Their unhappy experience with the unfair printer manager from section 1.3 triggered their decision to share a variable turn keeping track of who has the risn seo a is thus modeled by the automaton on figure 1.16. The automaton describing the behavior of user B is of course symmetrical (see figure 1.1 if turn-B, printB turn := A Fig. 1.17. The user B