The Alias property indicates whether this instance represents the base port address or one of the ranges with an alias. A ...

The Alias property indicates whether this instance represents the base port address or one of the ranges with an alias. A base port address is a predetermined port address dedicated to a specific service or device. A port alias address is one that a device responds to as if it were the actual address of an I/O port. 
Values: TRUE or FALSE. A value of TRUE indicates this instance represents an address alias.