| 摘要 |
An information retrievel system includes a video display terminal controlled by a local microcomputer which controls the major functions thereof and is connectable in a network with other such video display terminals which function as selected purpose variable function terminals by utilizing the instructions for the local microcomputer which come from a remote central data source as data so that the user can request a particular function, that is a program or set of instructions for the microcomputer as well as being able to request certain data from the data source. This set of instructions is transmitted over the same media as data and has the same format as the data, such as a pseudo video digital scan line when utilized with a row grabbing video display terminal transmitted over cable. The set of instructions is locally stored until erasure at the terminal, such as in a RAM, for locally controlling the functioning of the microcomputer. This program may be replaced or modified by requesting a different program to select a different purpose for the terminal. A ROM permanently stores the loader and executive program for the terminal and may normally operate the terminal as a row grabbing video display terminal except when a program is requested for selecting a different purpose for the terminal in which instance the called program or set of instructions is stored in the RAM and, when the entire requested program has been loaded, control is turned over from the ROM stored loader program to the newly entered called program which operates the terminal in accordance with the selected purpose. This RAM stored program may be erased to enable normal functioning as a row grabbing video display terminal if desired or may be replaced by a different selected program by depression of the appropriate keys on the keyboard. The system could be a one way communication system in which instance the data and programs are continuously transmitted in repetitive fashion from the remote data source including updated information in a real time environment or, if desired, could be implemented in a two way system.
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