#define FALSE 0
#define TRUE  1
#define N     2                      /* number of processes */

int turn;                            /* whose turn is it? */
int interested[N];                   /* all values initially 0 (FALSE)*/
void enter_region(int process)       /* process is 0 or 1 */
{
     int other;                      /* number of the other process */
     other = 1 - process;            /* the opposite of process */
     interested[process] = TRUE;     /* show that you are interested */
     turn = process;                 /* set flag */
     while (turn == process && interested[other] == TRUE) /* null statement */;
}
void leave_region(int process)       /* process: who is leaving */
{
     interested[process] = FALSE;    /* indicate departure from critical region */
}