from order placement to commissioning. GEC 4000 series computers were capable of running a number of operating systems but in practice Prestel machines exclusively ran OS4000 which itself was developed by GEC. This in turn supported BABBAGE, the so-called high level assembler language in which all the Prestel software for both IRC and UDC machines (and later the messaging machine) was written. In 1987, a Prestel Admin computer was introduced which supported the user registration process: the capture of user details from the paper Prestel Application Form (PAF), the transfer of data to the relevant Prestel computer, and the printing of the welcome letter for users. This machine, also based upon GEC 4082 equipment, was the first to be equipped with 1 Mbyte of memory which was required to support the Rapport relational database. This product from Logica was an early example of deployment of a system written in a 4GL database language which supported all features of the Prestel Admin application. Monitoring equipment In order to proactively manage the potentially large numbers of user connections to Prestel computers, special monitoring equipment was developed by Post Office research and development engineers. This was known by the acronym VAMPIRE, short for Viewdata Access Monitor and Priority Incident Reporting Equipment – a title which more or less describes its function. The device used private circuits to connect modem ports on each computer or remote IRC multiplexor node, with a display on a television screen Prestel Prestel at the Regional Centre responsible for the administration of IRC. The VAMPIRE screen consisted of a matrix of small squares, so arranged that all ports for a single IRC computer could be displayed on a single television with each square representing the state of a port simply by means of the colour. Free ports were shown as green, occupied ports as yellow, incoming calls as pale blue and faulty ports as red, such that the state of a whole Prestel machine or concentrator node could be determined at a glance. It was apparently planned to extend this facility via a system designated the Data Recording and Concentrator Unit for Line Applications known as DRACULA, which would generate a summary view so that the state of multiple computers could be displayed on a single screen. This device was never deployed since the number of VAMPIRE sets needed to monitor every Prestel computer and concentrator never got beyond