OK, to bring you up to speed.
Forum etiquette is in place for several reasons - none of which you are aware - because you didn’t read the ‘posting’ guidelines.
Modifying previous posts is a no-no, because you disrupt the chain of reading and developing a solution… and you can make subsequent posts look silly because you have changed the reason for replying.
Posting your code in-line with
tags is preferable, but if the code is too large, attach it as you did - but - as a text file (ino is text, but can’t be opened by many people that are trying to help you).
for(start = 0; start <= 35; start++)eeprom_data[start] = EEPROM.read(start);
Reads EEPROM addresses 0–35 into an array called eeprom_data, which isn’t really all that helpful, because EEPROM reads are pretty fast anyway.
The code is comprehensive, but I can see a few places where it is unnecessarily wordy or slower than needs to be, but that’s not your question.
To answer that - there is NOWHERE in that code which WRITES to the EEPROM, so I’m guessing the original author has a separate program he used to calibrate the system - which writes the ‘constants’ to the EEPROM before this code is loaded and run. Which in turn may be a huge waste of effort, as the constants are constant - so why use EEPROM, when they could be stored in PROGMEM with a little thought & effort ?