Text editor using insert, update and delete structures for undo and redo operations

Claim 1

A text managing system for performing an editing operation of a text, by using a text editing program in a computer system, said text managing system comprising: text operation means for receiving at least one of insertion, update and deletion information for the text, as instructed by an operator, and for displaying the result of editing the text on a screen; UNDO/REDO control means, operatively connected to said text operation means, for restoring the text to be displayed on said screen to a most recent previous state, said previous state existing prior to a result of the editing, and for reexecuting the text restored as a result of said restoring; text processing means, operatively connected to said UNDO/REDO control means, for managing the text already edited during the editing operation in response to said UNDO/REDO control means; a text management block, for managing current text, comprising a plurality of entries of pointers to a plurality of UNDO texts; each of said plurality of UNDO texts comprising an ID field, an ADDRESS field and a CONTENT field, said ID field storing a type of the UNDO text, said ADDRESS field storing a pointer to one of said plurality of entries of said text management block and said CONTENT field storing a character-string data being edited; an UNDO management table, operatively connected to said UNDO/REDO control means, for storing in correspondence with each editing operation which is performed, a corresponding UNDO level indicating the number of the UNDO operation; and a plurality of UNDO management blocks, each storing a plurality of pointers and each pointer pointing to one of said plurality of UNDO texts.