A user-oriented computer-based information retrieval system which would not require a computer specialist as an interface between computer and user was developed. The PLATO system was chosen because it was a high-speed computer-based man-machine interaction system with convenient visual display, keyset input device, versatile programing capability, time-shared on-line editing capability, and a logical program structure of interconnecting units. Coding Theory was selected as the subject area in which the example was carried out. The retrieval program developed allowed searchers to make queries and receive answers at the terminal, using a simple "dialogue" logic program. Highly structured query paths leading to the data base were built, although the ultimate system goal will be to have natural language capability. The model retrieval system was successful because it provided rapid responses, fostered simple user-computer interactions, permitted expansion of user questions, allowed algorithmic functions to be employed, and stored a history of interrogatory events for use in the subsequent modification of the retrieval strategy. (PB)