For video game RPGs, I've seen the following systems
1. Everyone gets the same amount of EXP
2. You have an active party of everyone you can bring, and a non-active party of everybody else. Your active party gets the same amount of EXP, no one else gets any.
3. The active party gets the same amount of EXP, the non-active party gets a smaller fraction (like 80%)
In all the above, dead people get no exp, and having dead people doesn't give anyone else more EXP, even though there's fewer people to take it.
In MMORPGs, it's often split based on character level within the party, with higher levels getting more to mitigate people power-leveling lower level players. I think most MMORPGs multiply the EXP based on the number of people in the party before splitting it - that way, although you get less exp per monster, when you add up the contributions from everybody it works out to more exp for everyone.