Computerized instruction has captured the interest of many educators as a means of individualizing language study for their students. The quality of this individualization is maximally dependent on the degree to which a computer can understand what the student communicates to it usually by typing a message on the keyboard. This article provides an overview of this student communication, or input: its types, its recognition, and some uses of its recognition. A general understanding of the potential of student-computer interaction will enlighten those who are examining Computer Assisted Language Learning (CALL) lessons for use in their curriculum. Some of this potential has been realized in the numerous foreign language lessons currently in use on the PLATO IV system at the University of Illinois at Urbana-Champaign.