Are slot machines purely random or do they pre-calculate every spin?

I was sitting here trying to decide which slot to play and googled random slot picker and this is what popped up Slot machines · Roulette

This slot machine is unlocked pretty early in the game, and players can use in-game currencies to roll for a random chance at getting a reward

random number generator slot 7s Wild is very much a retro-styled slot game, showcasing symbols like 7s, Bells, and Cherries that characterized classic slot machines random outcome

random slot generator random outcomes are central to this modeling technique, as they are to games like roulette, dice, and slot machines The technique was initially developed