Abstract: A fault-tolerant method of bottom-up editing whereby simultaneous display of the GUI view and source code view are available, and wherein real-time bottom-up editing is provided. In accordance with a preferred embodiment of the present invention, changes to the source code are isolated, first by isolating and analyzing source code according to groupings associated with the structure of the language used for the source code and then isolating and analyzing individual lines of source code within these groupings. If there are no errors in a particular grouping of source code, the changes in the grouping are automatically applied to the GUI. If errors are found in a grouping, the grouping is further analyzed to determine which lines contain the error. Semantic and syntactic errors are thereby isolated and, where found, are ignored. However, correct lines of the source code are also identified and thereby applied to the GUI for interpretation and display.