Which Computer Is Used A Handheld Operating System?

Which Computer Is Used A Handheld Operating System? Examples of Handheld PC devices are the NEC MobilePro 900c, HP 320LX, Sharp Telios, HP Jornada 720, IBM WorkPad Z50, and Vadem Clio. Also included are tablet computers like the Fujitsu PenCentra 130, and even communicators like the late Samsung NEXiO S150. What are the 3 types