This program will ask the user to input 10 signed decimal integers.
then calculate and display them, their sum and their average value.
The input will be read as a string then covert to number and be validated whether it has
non-digits (beside '+' or '-') or is too large for 32 bit
- includes ReadVal and WriteVal procedures for signed integers to convert string to integer and integer to string.
- includes getString and displayString macros that exclusively have ReadString and WriteString