Format of HEART.COM buffer:
Offset	Size	Description	)
 00h  8 WORDs	table of colors/attributes (refer to notes above)
 10h	BYTE	flags
		bit 0: program is in critical section, so flash double
		      exclamation mark
		bit 1: program is in safe code, so flash the heart character
 11h	WORD	position of heartbeat on screen, normally 009Eh (last column
		of second line)