Processors were the second of the three ranks of a Mentat order. They teamed to combine, divide, sort, and file pieces of discrete information with 99.99985% accuracy per 10,000 items, capable of introducing order and regularity to seemingly unrelated sets of information.
Gilbertus Albans, the founder of the Order noted that the clear danger to Processors was that the order they introduced ought or might not accord with reality therefore they were trained to attempt first to use the categories and labels that others provided. The sorting, sifting, and retrieving of information, as well as the ability to connect it with specific names places, or events was valuable beyond estimation in the anti-computer culture of the times.
Of the three ranks, Processors were the most vulnerable. Their training stressed unquestioning acceptance of the direction of others, and they were therefore totally dependent on the good will of those around them. In the Training House they were safely in the care of the Order until they progressed to the relative security of the third rank, Hypothesist.
While still on Septimus, there were stories of Processors being kidnapped (no difficult task) for carnival sideshow curiosities. One story says about how a group of five Processors became separated from the main party. The group asked a passerby how to find the city's sport stadium to meet the others. The man pointed to a band of gladiators whom the Processors followed up into the arena, and were killed in the melee of the day's program.