So, the question is, if I understand it correctly: which variables would a computer program need to store in order to create a save file for a single game of D&D?
It's probably good to split it into global values and things that are stored per character.
Per character:
HP
base stats
skill points per skill (and left over or total) (if 3.5)
money/gold pieces
number of items per owned item type
Global:
Hours until events
Number of dragons to slay to fulfill the prophecy
"how often has the party pissed off the king counter"
Stuff like that?