Learning advice

Hi I need some help with my project on Arduino uno

When I write this code to CMD it only writes the data to data.txt but not showing it me, I want the opposite (see the data but not save it)

mode COM4 BAUD=9600 PARITY=n DATA=8 echo d >COM4 COPY COM4 data.txt

and I want to make a small widget to show the output, which program should I learn?