In this scheme, the full range of addresses may be available for both.
The address refers to a memory location or an I/O device is specified with the help of a command line.
In general 
command line is used to identify a memory location or an I/O device.
if =1, it indicates that the address present in address bus is the address of an I/O device.
if =0, it indicates that the address present in address bus is the address of a memory location.
Since full range of address is available for both memory and I/O devices, so, with 16 address lines, the system may now support both 2 16 memory locations and 2 16 I/O addresses.