external                 Declares Assembly Language Procedure or Function[TP]

 procedure <pname1>(<parameters>); external <filename>;
 procedure <pname>(<parameters>); external <pname1>[<offset>];
 function  <fname>(<parameters>) : <ftype>; external <pname1>[<offset>];

    Turbo Pascal lets you call assembly language subprograms (procedures
    and functions). You declare these in your Pascal program by giving the
    procedure or function header as you would for a Pascal subprogram,
    followed by an EXTERNAL statement.

      <filename>    The name of a .BIN file containing the machine code of
                    assembly language routines.

        <pname1>    The name of the first routine in <filename>. This need
                    not correspond to the actual name of the assembly
                    language routine; this is the name you will use in
                    your Pascal program.

 <pname>,<fname>    The names of additional routines in <filename>.

        <offset>    The offset (in bytes) of the entry point for that
                    routine from the base address of <filename>.

  -------------------------------- Example ---------------------------------

    The examples below are taken from GRAPH.P, the header file for all
    extended graphics routines. The code for those routines is in the file
    GRAPH.BIN.

           procedure Graphics;                            external
           'GRAPH.BIN';
           procedure Plot(X,Y,Color : Integer);           external
           Graphics[21];
           function GetDotColor(X,Y : Integer) : Integer; external
           Graphics[42];