500分求助高手帮忙，改写机读卡接口程序！！！！！

我的前台是delphi,后台是  sql,这是我的一个连接：机读卡的接口程序，但是连的时候有问题，格式文件选择后，不能读出正确的信息。例如，我的答题卡没有填写学号，课程号的信息时，按照程序原来设定，该是机子不读卡，给出提示信息，但是运行时没法给用户提示，机子进入死循环。
procedure Tfrm_jqdk.BitBtn1Click(Sender: TObject);
var
    cmd:array[0..254] of char;
    buf:array[0..254] of char;         //数组
    Sp: array[0..199] of char;
    I:integer;
    lsStr:string;
    temp:pchar;
    ErrNum:integer;
    Maxnum,start:integer;
begin
    try
        if cob_class.Text <> emptystr then
        begin
            str:= path + '\setup.ini';
            fomfilename:=getinifile(str,'fomfile','filename');
            start:= strtoint(getinifile(str,'fomfile','start'));
            aid:=getinifile(str,'counter','aid');    //答题卡序号
            if fomfilename<>emptystr then
            begin
                timer1.Enabled:=true;
                temp:= pchar('S '+ fomfilename + '/');  // FOMFILE.FOM为发送格式文件名
                OmrS(temp);
                OmrG(buf);
                I:=0;
                if copy(buf,1,2)='08'   then
                begin
                    pbar.Position:=0;
                    timer1.Enabled:=false;
                    exit;
                end;
                while true do
                begin
                    fillchar(sp,200,ord(' '));
                    cmd:='/ ';
                    omrs(cmd);
                    omrg(buf);
                    if copy(buf,1,2)='OK' then
                    begin
                        strpcopy(cmd,'001'+sp+'/');
                        omrs(cmd);
                        omrg(buf);
                        if (i<=22)then //检测学号和课程号有没有涂写。前 8位是学号，后面的课程号！
                            if buf[i]=emptystr then
                            begin
                                application.MessageBox('提示','该答题卡无效',0);
                            end
                            else
                                i:=i+1;
                            if buf[i]<>emptystr then
                            begin
                                sid:=buf[1]+buf[2]+buf[3]+ buf[4]+buf[5]+buf[6]+buf[7]+buf[8];
                                cid:=buf[1]+buf[2]+buf[3]+ buf[4]+buf[5]+buf[6]+buf[7]+buf[8]+buf[9]+buf[10]+buf[11]+ buf[12]+buf[13]+buf[14]+inttostr(8);
                            end;
                        end;
                    if (strtoint(aid)>0) and (strtoint(sid)>0) and (strtoint(tmid)>=0) then
                    begin
                        with datam.qry_answer do
                        begin
                            close;
                            sql.Clear ;
                            sql.Add ('select cid,sid,sk from answer order by sid asc');
                            prepare;
                            open;
                            first;
                            while not eof do
                            begin
                                with datam.qry_answer do
                                begin
                                close;
                                sql.Clear;
                                sql.Add('insert into answer (tmid,sid,cid,aid,sk)');
                                sql.add(' values (:tmid,:sid,:cid,:aid,:sk)');
                                parambyname('sid').asstring:=sid;  //填入学号
                                parambyname('cid').asstring:=cid;//填入课程号
                                datam.qry_class.FieldValues['classid'];//插入班级号
                                parambyname('tmid').asstring:=tmid;//题目序号
                                parambyname('aid').asstring:=aid+inttostr(1);
                                parambyname('sk').AsString :=buf[start];//学生的答案
                                prepare;
                                execsql;
                                end;
                                start:=start+1;
                                next;
                            end;
                            if not (putinifile(str,'counter','sid',inttostr(strtoint(aid)+1))) then
                            begin
                                application.MessageBox('提示','写配置文件出错！',0);
                            end;
                            lb_num.Caption:=inttostr(strtoint(aid)+1);
                        end;
                    end;
                end;
                end
                else begin
                    ErrNum:= strtoint(copy(buf,1,2));
                    case ErrNum of
                    5  : begin
                        application.MessageBox('提示','检测点线错，数据未读入。',0);
                        timer1.Enabled:=false;
                        end;
                    3  : begin
                        application.MessageBox('提示','双张错，数据未读入。',0);
                        timer1.Enabled:=false;
                        end;
                    7  : begin
                        application.MessageBox('提示','卡纸或同步信号错，数据未读入。',0);
                        timer1.Enabled:=false;
                        end;
                    4: begin
                        application.MessageBox('提示','类型标志错，数据未读入。',0);
                        timer1.Enabled:=false;
                        end;
                    else  application.MessageBox('提示','缺卡，加评议卡后按开始按钮',0);
                    cmd:='-/';
                    omrs(cmd);
                    exit;
                    end;
                end;
        end
        else
            application.MessageBox('提示','请先指定格式文件！',0);
except
    cmd:='-/';
    omrs(cmd);
    application.MessageBox('警告','故障',0);
end;
end;procedure Tfrm_jqdk.Timer1Timer(Sender: TObject);
begin
    pbar.StepIt;
    if pbar.Position  =pbar.Max then
        pbar.Position:=0
end;procedure Tfrm_jqdk.FormActivate(Sender: TObject);
begin
    setcob;
    str:= path + '\setup.ini';
    lb_num.Caption:=getinifile(str,'counter','aid');
end;
end.