A display oriented programmer's assistant

This paper continues and extends previous work by the author in developing systems which provide the user with various forms of explicit and implicit assistance, and in general cooperate with the user in the development of his programs. The system described in this paper makes extensive use of a bit map display and pointing device (a mouse) to significantly enrich the user's interactions with the system, and to provide capabilities not possible with terminals that essentially emulate hard copy devices. For example, any text that is displayed on the screen can be pointed at and treated as input, exactly as though it were typed, i.e., the user can say use this expression or that value, and then simply point. The user views his programming environment through a collection of display windows, each of which corresponds to a different task or context. The user can manipulate the windows, or the contents of a particular window, by a combination of keyboard inputs or pointing operations. The technique of using different windows for different tasks makes it easy for the user to manage several simultaneous tasks and contexts, e.g., defining programs, testing programs, editing, asking the system for assistance, sending and receiving messages, etc and to switch back and forth between these tasks at his convenience.