Following earlier tablet computer products such as the Pencept PenPad, and the CIC Handwriter, in September 1989, GRiD Systems released the first commercially successful tablet computer, the GRiDPad. All three products were based on extended versions of the MS-DOS operating system. In 1992, IBM announced (in April) and shipped to developers (in October) the 2521 ThinkPad, which ran the GO Corporation's PenPoint OS. Also based on PenPoint was AT&T's EO Personal Communicator from 1993, which ran on AT&T's own hardware, including their own AT&T Hobbit CPU. Apple Computer launched the Apple Newton personal digital assistant in 1993. It used Apple's own new Newton OS, initially running on hardware manufactured by Motorola and incorporating an ARM CPU, that Apple had specifically co-developed with Acorn Computers. The operating system and platform design were later licensed to Sharp and Digital Ocean, who went on to manufacture their own variants.