The first known correct software solution to the critical-section problem for two processes was developed by Dekker. The two processes, P0 and P1, share the following variables:

boolean flag[2];

/* initially false */ int turn;

The structure of process Pi (i == 0 or 1) is shown in Figure 5.21. The other process is Pj (j == 1 or 0). Prove that the algorithm satisfies all three requirements for the critical-section problem.