Terminal controller

A terminal controller in combination with at least one video terminal for allowing concurrent operations of a plurality of application programs, each said application program using an input/output data stream including an address information which enables to display data on the overall screen of a video terminal;

• comprising:
• first input/output buffer means for application program to perform a data input/output operation with a first application program;
• second input/output buffer means for application program to perform a data input/output operation with a second application program;
• input buffer means for a video terminal for storing an input data stream input from the video terminal linked with said terminal controller;
• output buffer means for the video terminal for storing an output data stream to be output to said video terminal;
• means for setting a screen split operation mode in response to a special control input information input from said video terminal;
• means for storing an information input from said video terminal on a screen split boundary of said video terminal;
• first address conversion means for converting at least a portion of an address information in an input data stream stored in said input buffer means for the video terminal according to said stored boundary information and for distributing said converted data to said first and second input/output buffer means, when said screen split operation mode is set by said mode setting means;
• and
• second address conversion means for fetching a portion of each said data stream stored in said first and second input/output buffer means, for converting at least a portion of said address information according to said stored boundary information, for composing an output data stream corresponding to the overall screen of said video terminal and for transferring said composed output data stream to said output buffer means for the video terminal when said screen split operation mode is set by said mode setting means.