METHOD AND SYSTEM FOR ALLOWING MULTIPLE USERS TO SIMULTANEOUSLY EDIT A SPREADSHEET

In association with a computer system, a method and system for allowing multiple users to simultaneously edit a spreadsheet. Multiple users access a spreadsheet stored in a disk file and make independent changes to the spreadsheet. Changes are stored in respective memory change logs on each user's computer. When a user performs a save operation, the contents of the memory change log are appended to a disk change log in the disk file. When each user performs a save operation, each user's changes, as maintained in each respective memory change log, are appended to the disk change log. Conflicting changes that cannot simultaneously exist in the spreadsheet in the disk file are identified and resolved by allowing the user to select the winning action or automatically selecting the most recent action as the winning action. Losing actions in the memory change log are deleted and losing actions in the disk change log are effectively canceled by applying an inverse action to the losing action. Each inverse action is stored in a disk undo log stored in the disk file.