init:
	Select a filename.

	Create XSI semaphore array {S = 0, W = 0, X = 1 and Q = 0}
	with random key. Store the semaphore array's key in
	decimal form on the first line in the selected file.

	Create XSI shared memory, with an allocation of 2048 bytes,
	with a random key. Store the shared memory's key in
	decimal form on the second line in the selected file.


broadcast:
	with P(X):
	  Z(W)
	  Write NUL-terminate message to shared memory
	  Q := 0
	  Z(S)


listen:
	V(S) with undo on exit
	forever:
	  V(Q)
	  Z(Q)
	  Read NUL-terminated message from shared memory
	  if breaking:
	    P(S) with undo on exit
	    break
	  with V(W):
	    with P(S):
	       Z(S)