对文本文件进行写操作，当文本文件的文件名为“LPT”或“COM”等保留字里，即是对指定端口写。
my:='lpt1';
filehandle:=fileopen(my,fmopenwrite);
fileclose(filehandle);
if filehandle<0 then
begin
messagebox(handle,'lpt1错误','错误',mb_iconerror);
exit;
end
else
begin
assignfile(tf,my);
rewrite(tf);
writeln(tf,chr(27)+chr(112)+chr(0)+chr(18)+chr(22));
with query1 do
begin
sql.Clear;
sql.Add('select 企业名称 from 企业档案');
close;
open;
end;
writeln(tf,' '+query1.fieldbyname('企业名称').AsString);
if strtofloat(label6.Caption)<0 then
writeln(tf,' '+'退货单')
else
writeln(tf,' '+'销售单');
writeln(tf,'流 水 号:'+form1.StatusBar1.Panels[1].Text);
writeln(tf,'销售日期:'+datetimetostr(now));
writeln(tf,'收 款 员:'+form1.StatusBar1.Panels[3].Text);
writeln(tf,'--------------------------------');
writeln(tf,'商品编码'+' '+'数量'+' '+'单价'+' '+'金额');
writeln(tf,'--------------------------------');
for a:=1 to form1.StringGrid1.RowCount-2 do
begin
writeln(tf,form1.StringGrid1.Cells[2,a]);
writeln(tf,form1.StringGrid1.Cells[1,a]+' '+form1.StringGrid1.Cells[5,a]+' '+form1.StringGrid1.Cells[4,a]+' '+form1.StringGrid1.Cells[6,a]);
end;
writeln(tf,'--------------------------------');
writeln(tf,'合计金额:'+' '+Label8.Caption);
writeln(tf,'找零金额:'+' '+label9.Caption);
writeln(tf,'谢谢惠顾,欢迎下次光临');
writeln(tf,'请妥善保管您的电脑小票');
writeln(tf,'');
writeln(tf,'');
writeln(tf,'');
writeln(tf,'');
writeln(tf,'');
closefile(tf);
责任编辑：小草
