An ASCII text file (with the extension .inc) that can be imported into a Text Design File (.tdf) by an AHDL Include Statement. The AHDL Include File replaces the Include Statement that calls it. AHDL Include Files can contain Function Prototype, Define, Parameters, or Constant Statements. AHDL Include Files that contain Function Prototypes for Altera-provided megafunctions are located in the \quartus\libraries\megafunctions and \quartus\libraries\others\maxplus2 directories created during installation.
When you use a Module Instantiation in Verilog HDL, the Compiler uses the port name and order information in AHDL Include Files that contain Function Prototypes to implement an instance of the logic function.