Converter from heximals

The initial txt file has heximal numbers, separated by comas. Create a program that could convert each number to octals, decimals and to complementary code. User has to chose what he wants to convert these numbers to. (for example in window he has to type 1 for converting to octals, 2 for heximals and etc.) The program shouldn't be extraordinary, I want it to be easy to comprehend as a non programmer. I also want you to give explanations after each line . After completing the program, program's block scheme written accordingly to world standards is also needed