In order to meet the information retrieval needs of various industries, inquiry-response systems are being implemented by storing large data bases in centralized computer files. In some systems, the files are accessed by personnel primarily as the result of telephone calls from customers. As an example, in the airlines industry, computer files are accessed by reservation clerks to determine the availability of reservations for a specific flight. In this example, and in similar applications involving queries or requests from customers, input messages requesting certain information are generated by a customer representative and then transmitted to a computer from an input-output terminal such as a visual display device. When the computer has obtained the requested information, a response message is transmitted back to the requesting terminal, and the representative continues her dialogue with the customer.