The rapid increase of requirements for data communication in the current industrial society has brought development of various technologies of data communication. Among them, line-sharing message concentration message switching and communication preprocessing technologies by was of a minicomputer have been presented in order to obtain effeicient utilization of data links and resource sharing of a host computer in a data communication system. To meet these requirements and to obtain the utilization, and resource sharing, a new system, UNIVAC-NOVA Data Communication System(UNDCS), which uses the TTY model ASR 33 as a remote terminal and supports multiple terminals simultaneously has been designed and implemented on NOVA 840. Moreover, UNDCS as a communication preprocessor has been programmed to handle the terminal which is one of remote terminals supported by operating system of UNIVAC 1106 (EXEC 8). Therefore, UNDCS software was developed which: 1) provides the basic handlers that maintain interruption from data links, reception and transmission of messages, and buffer management; 2) performs various functions for message concentration and message switching; 3) provides all required message format and line protocol control characters required to conform to UNIVAC requirements in synchronous transmission of data and 4) services the demand processing of EXEC 8. This dissertation documents how the objectives, message concentration and switching, communication preprocessing, and service have been achieved.