Segments flagged with the ALIAS keyword can be addressed using the 16-bit segmented method (_far16), or the 32-bit linear method. The loader must prepare an additional segment selector for each segment designated with the ALIAS keyword. This new segment selector allows for 16-bit addressing.
Example:
SEGMENTS _CODE ALIAS
The statement above specifies that the segment _CODE can be called using 16-bit far calls and 32-bit near calls.