Promela and Model Description
. Important aspects of Promela
   1) Executability
       In Promela, execution of each statement depends on its executability.
       Thus it provides a basic method of synchronization by providing the
       concept of critical section
ex1:  (a==b) will execute only if it’s true.
ex2:  proctype A() {    x = true; t = Bturn;
        (y == false || t == Aturn);
        /* critical section */
       x = false }
           proctype B() {   y = true; t = Aturn;
      (x == false || t == Bturn);
    /* critical section */
      y = false }
          init { run A(); run B() }