Abstract: A terminal control system comprises a control equipment and a plurality of terminals. The processing program held in the control equipment is loaded to each terminal which performs data processing in accordance with the loaded program. Each terminal has a memory for storing modification data for modifying the program to a program having another function. The processing program loaded to a terminal from the control equipment is thus modified to another kind of program by the modification data to provide the terminal with another function. The original function of a terminal is thus capable of being modified or improved by this modification program.

Abstract: A terminal apparatus for handling data by the field. Each field comprises a field defining character for defining an attribute of the field and a certain number of field data following the character. Information for determining the meaning of the field defining character is retained in the terminal apparatus and the attribute of the field is determined by the combination of the information and the field defining character. As a result, many field attributes can be specified.

Abstract: A data input apparatus comprises a display device for displaying guidance information which designates types of data to be inputted as well as the order therefor, a key set having a plurality of keys arrayed in a matrix and a corresponding number of mats defining the functions of the individual keys which can be imparted with new definitions by changing over the associated mats, and a circuit adapted to select and change the mats defining the keys so that the various types of data indicated by the guidance information can be inputted in the order given by the guidance information. The mats can thus be replaced by other proper ones automatically without resorting to manual operation.