procedure TForm1.Button1Click(Sender: TObject);
const
 str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0987654321';
var
 i, i2: integer;
 z: integer;
 temp_str: string;
begin
 for i:=1 to strtoint(edit1.Text) do
  begin
    temp_str:='';

    for i2:=1 to 8 do
     begin
       z:=random(length(str));
       temp_str:=temp_str+str[z];
     end;

    Memo1.Lines.Add(temp_str);
  end;
end;