4DOS 有个读屏变量函数
4DOS Help Topic: @READSCR
@READSCR: Returns the text displayed on the screen at the
specified location. The upper left corner of the screen is location 0,0.
The row and col can be specified as an offset from the current cursor
location by preceding either value with a or . For example:
%@readscr
returns 10 characters from the screen, starting 2 rows above and 2 columns
to the right of the current cursor position.
You can also specify the row and column as offsets from the current cursor
position. Begin the value with a plus sign to read the screen the
specified number of rows below (or columns to the right of) the current
position, or with a minus sign to read the screen above (or to the left
of) the current position.
以前 4DOS 还没有 Freeware 的时候我就用这个笨办法来判断它自己是否试用到期来提醒你,然后再用原始的文件替换掉它自己的过期记录文件,然后可以一直试用下去。但这个方法好像只对 6.x 有效,后来的 4DOS 忘了从哪个版本起不是记录在文件里了,不知道是记录在哪里了,就无效了。