I would like to make the following suggestion for a challenge:
Create a fully functional calculator (8-digit, basic calculator, not scientific) but do all the calculations by hand...meaning that if the user wants 356 * 8...the program should multiply 8*6 then 8*5+4 then 8*3+4. Just like you would do it if you had to multiply with pencil and paper. This would require addition, subtraction, multiplication and division and as an added challenge, negative numbers.
I wrote the first beta program for division by writing: PHW347.
This program can calculate correctly only special cases. I'm going to rewrite this program to more generic cases.
Thank you jherch77 for your challenge!