1307	 A Lightpen-Controlled Program For On-Line Data Analysis	 This paper describes a technique designed to ease the use of a data processing system by a person in particular a scientist who is intimately and primarily concerned with interpreting the significance of data handled by the system. Since such a person is often unable to spend the time necessary to master a programming language it is essential that he be aided in composing commands to the computer. In the system described the user is not required to learn or remember the vocabulary of the language because the vocabulary is displayed before him on menus by means of a computer-drive scope. He selects the various vocabulary elements required by pointing with the light pen. By use of a small unordered set of rewriting rules applied as a result of light pen selections the user generates only syntactically correct commands to the system. He does not have to learn or remember the grammar. The program restricts the user severely in the particular language he can use but the method for communicating with the program makes these restrictions seem quite natural and unconstraining. The program has been used successfully for over ten months.
