Due to its enormous number of distinctive logographs to be processed in a text, designing a "user friendly" system for the input of Chinese characters directly into computers is a challenge to both computer engineers and cognitive psychologists. This chapter examines problems encountered in the design of a graphemic input system for the Chinese writings. From knowledge accumulated over decades of research on human information processing, we tentatively propose a set of criteria to serve as an evaluation model for a graphemic input system. It is hoped that such a model can serve not only the function of evaluation but also that of diagnosis.