Originally a dissertation for the degree of Master of Science in the Department of Computation, UMIST (University of Manchester Institute of Science and Technology), U.K., 1981. This is a scanned copy of the original, January 2010. The dissertation specifies a set of computer programs to allow learners to interact with a computer through written language. It sets out the computational foundations for an approach later investigated in a Ph.D. thesis, Natural Language, Computer-Assisted Learning and Language-Impaired Children, by the same author, at the Department of Psychology, University of Hull, U.K., in 1987.