Encounter Flags and Item Mutation/Duplication

[rjaguar3]

Sorry, what are flags? I kinda get it but not...really...

When you encounter or capture a Pokemon, the game sets a bit in memory to notate that you have seen/caught that pokemon.  This way, the Pokedex will be able to accurately show all the Pokemon you've seen and caught.

This is all done by means of an array.  There are 19 bytes to store whether the pokemon have been caught, followed by 19 bytes to store seen pokemon.  Since there are 8 bits in a byte, each of these arrays can hold the data for 152 pokemon.  The game has a somewhat complicated way of determining which pokemon corresponds to which byte, but it basically follows that the higher the dex number, the later in memory the pokemon's bit will be.

This all works dandy if the dex numbers are from 1-151, as it should be.  But, since some glitches have a dex number outside of that range, it is possible for the game, when setting the bit to say "this pokemon has been encountered," sets a bit beyond the 19 bytes allocated for "encountered pokemon."  What happens to be stored after the pokedex encounter array is the list of items you have.  So an encounter with a glitch with dex number not from 1-152 (e.g. Missingno.) will change either the number of item slots you have, the quantity of an item, or the identity of an item.  These effects can be completely predicted by looking at the dex number, as I stated in my first post.

[Tombstoner]

Oh. So we all had seen this all along wjhen we first us4ed the MissingNo. trick...

[rjaguar3]

Oh. So we all had seen this all along wjhen we first us4ed the MissingNo. trick...

Yes.  In the most familiar case of Missingno., the bit that's affected by an encounter is the most significant bit of the quantity of the 6th item.  Hence, an encounter with Missingno. will add 128 to the sixth item quantity iff the item quantity is 127 or less.

[Tombstoner]

What exactly happens if it's already 127+? That's definitely happened for me before...

[rjaguar3]

What exactly happens if it's already 127+? That's definitely happened for me before...

In that case, when the game sets the bit to 1, it won't change anything, since it was already 1.  Hence, nothing would happen.

[Tombstoner]

Really? In my experience they seemed to have gone up to FF(well around that anyway, at least 200)... But i guess that must have been something else...what common thing might do that? Anybody know?

[rjaguar3]

Really? In my experience they seemed to have gone up to FF(well around that anyway, at least 200)... But i guess that must have been something else...what common thing might do that? Anybody know?

You probably had reduced your total to 127, which would allow you to add an additional 128 to make a total of 255.

[Tombstoner]

Gotcha. It wasn't exactly 255 because I must have used more than 1.

[Vitro]

Im guessing the encounter flag for missingno and 'M is what also causes the effect of your hall of fame. I wonder if its possible if other glitch pokemon effect other parts of the game as well.

[Tombstoner]

Im guessing the encounter flag for missingno and 'M is what also causes the effect of your hall of fame. I wonder if its possible if other glitch pokemon effect other parts of the game as well.

Probably not actually, because more or less every glitch (PkMn) screws up your Hall of Fame.