Hi Armin, thanks a lot of your kind info. I have tried, both are working. The #907 and #1035 are very helping. But got confuse regarding the command "z" and "e" in #907. I always got error regarding the two as below:
Unknown command: z
Unknown command: e
What is the meaning of the two commands? When I deleted both them, no more error at all.
Here are the data I used to plot a mathematical expression: y(t)=e^-t*cos(2*pi*t): That will plot a line following the coordinates. The first command (l-line), I replaced with pl-polyline and spline, they are both working well. So do those testing working well when I tested for "Load Command File" and "Paste Multiple Commands".
For this testing, the data below I did in Excel. Then I saved to Notepad to run "Load Command File", and thence I copied and pasted to the command line to run "Paste Multiple Commands".