No. 1 ESS ADF: Message Processing Program Organization

The No. 1 Electronic Switching System, Arranged with Data Features (No. 1 ESS ADF), is a stored-program system which uses the basic No. 1 ESS program organization with additional task programs, input-output equipment, and mass storage to provide a reliable switching arrangement for store-and-forward data service. To meet the needs of data switching, No. 1 ESS ADF must meet the stringent operating requirements of a telephone switching office1 in addition to meeting requirements that are unique to a data-switching office. The system must (i) respond rapidly in real time to the demands for service, (u) have the versatility to provide the large variety of service features demanded of a modern data-communication system, {Hi) be reliable, (iv) be capable of meeting the needs of different installations without modification of the basic program, and (v) be economically balanced in its use of real-time and storage facilities. In addition, the No. 1 ESS ADF must meet requirements beyond those imposed on telephone switching systems.2 Unlike line-switched systems, a message-switched system provides no end-to-end verifica2753