In the cognitive paradigm, learning an L2 is like learning any other skills, and it starts from the provision of input. Gass’ (1997) Computational Model provides a micro view of cognitive processing, which elaborates how a single input could be processed through five stages. McLaughlin’s (1987, 1990) and Anderson’s (1983, 2000) Models provide a macro view of how the knowledge system is built up through numerous instances of simple processing and is eventually used automatically by L2 learners. The potential roles of written CF will be emphasized within the models and the impacting factors will be extrapolated through relevant notions and hypotheses.