procedure CreateForm(FormClass:TFormClass;Var reference);
作用：在应用程序中创建一个新的窗体
在其参数中FormClass用来制定窗体类型，而Reference是所建立
窗体的一个变量。
动态建立窗体
program project;
...
begin
application.initialize;
application.CreateForm(TForm1,Form1);
//省略Form2,Form3的建立
application.Run;
end;
Unit Unit1;
....
implementation
uses
unit2,unit3;
{$ *.DFM}
Funcation Hasform(a:String):boolean;
var
R:Boolean;
X:Integer;
Begin
r:=false;
for x:=0 to screen.formcount-1 do
begin
if screen.forms[x].name =a then
r:=true;
end;
result:=r;
End;
procedure form1.button1click(sender :tobject);
begin
if not hasform('form2') then
begin
applicaton.createform(Tform2,form2);
showmessage('Form2窗体建立!');
end;
end;
procedure form1.button2click(sender:tobject);
begin
if not hasform('Form3') then
begin
application.createform(Tform3,form3);
showmessage('Form3建立!');
end;
end;