Pascal 中怎样实现文件读写和创建文件??谢谢

uses System;
//.....var   F: TextFile;
  S: string;
begin
  if OpenDialog1.Execute then          { Display Open dialog box }
  begin
    AssignFile(F, OpenDialog1.FileName);   { File selected in dialog box }
    Reset(F);
    Readln(F, S);                          { Read the first line out of the file }
    Edit1.Text := S;                       { Put string in a TEdit control }
    CloseFile(F);
  end;
end;在delphi中还可以uses Sysutils;procedure TForm1.Button1Click(Sender: TObject);var
  iFileHandle: Integer;
  iFileLength: Integer;
  iBytesRead: Integer;
  Buffer: PChar;
  i: Integer
begin
  if OpenDialog1.Execute then
  begin
    try
      iFileHandle := FileOpen(OpenDialog1.FileName, fmOpenRead);
      iFileLength := FileSeek(iFileHandle,0,2);
      FileSeek(iFileHandle,0,0);
      Buffer := PChar(AllocMem(iFileLength + 1));
      iBytesRead = FileRead(iFileHandle, Buffer, iFileLength);
      FileClose(iFileHandle);      for i := 0 to iBytesRead-1 do
      begin
        StringGrid1.RowCount := StringGrid1.RowCount + 1;
        StringGrid1.Cells[1,i+1] := Buffer[i];
        StringGrid1.Cells[2,i+1] := IntToStr(Integer(Buffer[i]));
      end;
    finally
      FreeMem(Buffer);
    end;
  end;
end;