Int. Y. Man-Machine Studies (1980) 13, 201-211 An application of file-comparison algorithms to the study of program editors P. ANANDAN,t D. W. EMBL•Y AND G. NAGY Department of Computer Science, University of Nebraska, Lincoln, Nebraska 68588, U.S.A. (Received 24 November 1979) Program editing is considered in terms of a file-comparison model that formalizes the transformation of an imperfect version of a program text into an improved version by means of editing operations. With some enhancement, existing file-comparison algorithms can produce the information required for the model. These enhancements include the introduction of logical levels in files, selection of a corresponding element among alternatives, and the detection and analysis of similarity. An algorithm that incorporates these modifications is described. Illustrative of the use of the file- comparison model, a high-level editing sequence for a particular text editor and a particular editing task is automatically produced and is found to be comparable to typical user-produced editing sequences. Potential applications of the file-comparison model to the study of program editors are outlined. 1. Introduction The spread of conversational computing has spurred rapid and chaotic development of program and text editors, but, by and large, these editors have not yet been subjected to the same degree of formal analysis and scrutiny as have procedural programming languages. Aiming at the development of a methodic approach, the objective of this paper is to demonstrate a hitherto unexplored application of file-comparison algorithms to the study of program editors. Most editors are system and even installation dependent; none has earned the confidence of a sufficiently large segment of the user community to warrant its widespread implementation. The burden of mastering several program editors--often necessary even within the same institution--is considerable, and it would therefore seem desirable to lay the foundations for investigating the behavior of this important component of time-shared computer systems. The present endeavor is an attempt to adapt existing file-matching algorithms to develop a relatively simple tool, the file-comparison model. Given an imperfect version of a program text and an improved version incorporating desired modifications, this tool allows us to isolate the necessary changes in a manner suitable for further analysis. 2. The file-comparison model The file-comparison model formalizes the transformation of a source file Fs into a target file Ft by means of editing operations. To provide a concrete illustration, the following t Current affiliation: INTEL, Aloha, Oregon 97005, U.S.A. 201 0020-7373/80/060201 + 11 $02.00/0 O 1980 Academic Press Inc. (London) Limited