Abstract: Multiple virtual images are built on a display screen of a text processing system by a display access method (DAM) program running interrupt identified service programs. Each of the service programs is provided with stack memory elements for retaining data to run the program. Each of the service programs is run by the DAM program in accordance with priority interrupts with a higher priority interrupt having immediate access to the DAM program. A service program having a low priority interrupt that is being run by the DAM program will be stopped by the occurrence of a higher priority interrupt with the data and address information of the interrupted program retained in the stack memory elements. The service program of the higher priority interrupt is then run and when ended the DAM program retrieves the data for the lower priority program to return to the point of interruption. This program of the lower priority interrupt is then run to an end if not again interrupted by a higher priority interrupt.

Abstract: Operator keystrokes are processed in a text processor system to put characters and symbols on a fixed pitch display screen without limitation as to other size characters or symbols on the screen. Keystroke data is processed under the control of programs stored in a random access memory. For a mixed pitch display, the random access memory of the system is structured to include a text storage buffer and a display control block both interconnected to an applications program and a display access method program. Data is stored in the text storage buffer in an unformatted configuration in a mixed pitch arrangement and the programs evaluate the data to display characters and symbols with correct character pitch. The programs also draw a scale line on the screen to provide character information to the operator.

Abstract: Operator keystrokes are processed in a text processor system to move a cursor on a display screen in either a vertical or horizontal direction or both without limitation as to the location of text. Keystroke data is processed under the control of programs stored in a random access memory. For a cursor motion, the random access memory of the system is structured to include a text storage buffer and a display control block both interconnected to an applications program and a display access method program. Data is stored in the text storage buffer in an unformatted configuration and the programs equate a contextual cursor address with a spatial cursor position. After running the display access method program in accordance with application program commands, a refresh buffer provides display signals to visually present by means of the display screen a cursor at an identified position in text.

Abstract: A text processing system includes a first external storage area for text documents, an internal text storage buffer where, inter alia, edit operations are performed, and a third storage area in which text is formatted for display. The area for formatting text for display is related to the internal text storage buffer by a table containing pointers to the text storage area, one for each line to be displayed. The pointers are expressed relative to a single known address, that of the start of the line in the text storage buffer containing the point at which the edit operation is to occur.

Abstract: A ghost cursor indicates the relative horizontal position on a display screen associated with a printed document rendition of the displayed text and control codes. In a normal, or hidden codes, mode of operation the ghost cursor, placed on an escapement scale line, is vertically aligned with a text cursor which is positioned adjacent the displayed text code which defines the present point of operation. In the all codes mode, all text and control codes (such as required backspaces, tabs, etc.) are displayed. In the all codes mode the ghost cursor indicates the relative horizontal position on the display screen of the code associated with the text cursor, with forward or reverse escapement indicated by the control codes taken into account.