Apple's development of a tablet computer began with the Newton MessagePad 100, which was introduced in 1993. The effort led to the creation of the ARM6 processor core with Acorn Computers. Apple also developed a prototype PowerBook Duo-based tablet computer named the PenLite, but did not release it to market as the company did not wish to affect sales of the Newton MessagePad. Apple released several more Newton-based PDAs, and discontinued the...