PRINT "Hex addresses for ports 0 to 3 from BIOS."
DEF SEG = 0
FOR x = 0 TO 3
   z = &H400 + x * 2
   p = PEEK(z)
   q = PEEK(z + 1)
   a = q * &H100 + p
   PRINT " COM" + STR$(x); ": " + HEX$(a)
NEXT
DEF SEG
