var  aHandle     : THandle;  aFileSize   : Integer;  aFileName   : String;procedure TForm1.Button3Click(Sender: TObject);begin    aFileName    := ‘C:\101\Java_new.pdf‘;    aHandle      := CreateFile(PChar(aFileName),GENERIC_READ, 0, nil, OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,0); // get the handle of the file    aFileSize   := GetFileSize(aHandle,nil); //get the file size for use in the  lockfile function    Win32Check(LockFile(aHandle,0,0,aFileSize,0)); //lock the fileend;procedure TForm1.Button4Click(Sender: TObject);begin    Win32Check(UnlockFile(aHandle,0,0,aFileSize,0));//unlock the file    CloseHandle(aHandle);//Close the handle of the file.end;