Pokémon Red Version, Blue Version, and Yellow Version - Last move chosen for use
The "last move chosen for use" changes when the player moves the cursor on the list of moves. The "last move chosen for use" is retained when a Pokémon leaves the battle (except when a battle ends). Each Pokémon in battle has a different "last move chosen for use" variable.
In Pokémon Stadium (known as Pokémon Stadium 2 in Japan), the controller of a frozen or sleeping Pokémon or a Pokémon that’s using a multi-turn attack can still select a move.
If a Pokémon was somehow forced not to choose a move for use in a turn, (for instance, when that Pokémon is asleep or is the opposing Pokémon of a multi-turn attack), then it simply doesn’t use any moves in that turn (unless the attack is Thrash, Petal Dance, Rage, Bide, a multi-turn attack, a two-turn attack, or Hyper Beam, and that Pokémon is continuing the attack). If a Pokémon can’t choose a move for use at the beginning of a turn, it chooses Struggle for use instead.