初识DELPHI DLL 之二

library test;

uses
  System.SysUtils,
  System.Classes;

{$R *.res}
function sum(x,y:double):double; stdcall; //stadCALL,表明，
//此类函数可在其它VB,VC 等调用
 begin
  Result:=x+y;
 end;

funCtion Minus(x,y:DOUBLE):DOUBLE;STDCALL;
BEGIN
  if X>Y    THEN
  RESULT:=X-Y
  ELSE
  RESULT:=Y-X;
END;
exports
  sum,
  minus;

begin
end.
按CTRL+F9编译；

以下是调用

unit Unit5;
interface
uses
  Winapi.Windows, Winapi.Messages, System.SysUtils,
  System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;
type
  TForm5 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    Button1: TButton;
    Edit3: TEdit;
    Edit4: TEdit;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form5: TForm5;
function sum(x,y:double):double; stdcall  ;external 'test.dll';//'test.dll'不在同一个路径的话，要加引用路径；
function Minus(x,y:double):double; stdcall ;external 'test.dll';//'test.dll'不在同一个路径的话，要加引用路径；
implementation
{$R *.dfm}
 procedure TForm5.Button1Click(Sender: TObject);
var
x,y:double;
begin
   if (edit1.Text='') or (edit2.Text='') then exit;
   x:=strtofloat(edit1.Text);
   y:=strtofloat(edit2.Text);
   edit3.Text:=floattostr(sum(x,y)); //相加
   edit4.Text:=floattostr(Minus(x,y)); //相减
end;

end.