1. A financial transaction system for physician's offices, the system comprising: a plurality of physician office terminals for location in physicians' offices, each terminal including a data entry means for entering medical insurance claim electronic data including at least patient identification data, medical service identification data, abbreviated routine medical service codes indicative of regularly performed medical procedures, physician identification data, and insurance carrier identification data, a modem means for transmitting the entered electronic data on a communications medium, and a terminal data processing means for processing the electronic data entered on the data entry means and providing the processed data to the modem means for transmission, the terminal data processing means including: a transaction library means for storing a record of entered medical claim data; a routine medical procedure library means for storing medical procedure details for services which are regularly performed in a medical procedure memory means, the medical procedure memory means being accessed by the abbreviated routine service codes to retrieve a more complete medical service description electronic data for transmission by the modem means, whereby only the abbreviated routine code is entered to cause a complete service description to be transmitted; a physician library means for storing physician identification details which are retrieved for transmission by the modem means, whereby physician identification details need not be entered for each entered medical claim; and, a central processing means for receiving data transmitted by the terminal modem means and processing the data to generate medical insurance claims.