再线等，请帮忙调试一个小程序段（case 语句）

Question

assignfile(f1,form1.Edit1.Text);
   reset(f1);
   assignfile(f2,form1.Edit2.Text);
   rewrite(f2);           readln(f1,head);
           headno:=strtoint(copy(head,1,3));
           while not eof(f1) do
                begin                   case headno of
                       200:
                           begin
                              writeln(f2,copy(head,4,length(head)-3));
                           end ;
                       210:
                           begin
                              writeln(f2,copy(head,4,length(head)-3));
                           end;                    end;                readln(f1,head);
                end;
          closefile(f2);
          closefile(f1);
//编译没有错误，但是没有结果。

Answer 1

你这段程序执行时，如果f1的第一行不是200，210开头的话，就不会有任何结果出现，
你得在while循环中取出headno的值。

Answer 2

assignfile(f1,form1.Edit1.Text);
   reset(f1);
   assignfile(f2,form1.Edit2.Text);
   rewrite(f2);           readln(f1,head);
           while not eof(f1) do
                begin
                   headno:=strtoint(copy(head,1,3));//HERE!!!!!!                   case headno of
                       200:
                           begin
                              writeln(f2,copy(head,4,length(head)-3));
                           end ;
                       210:
                           begin
                              writeln(f2,copy(head,4,length(head)-3));
                           end;                    end;                readln(f1,head);
                end;
          closefile(f2);
          closefile(f1);

Answer 3

我帮你整理代码：  assignfile(f1,form1.Edit1.Text);
  reset(f1);
  assignfile(f2,form1.Edit2.Text);
  rewrite(f2);  while not eof(f1) do
  begin
    readln(f1,head);
    headno:=strtoint(copy(head,1,3));
    case headno of
      200:
        begin
          writeln(f2,copy(head,4,length(head)-3));
        end ;
      210:
        begin
          writeln(f2,copy(head,4,length(head)-3));
        end;
    end;
  end;
  closefile(f2);
  closefile(f1);