Representing programs as text strings makes programming harder then it has to be. The source text of a program is far removed from its behavior. Bridging this conceptual gulf is what makes programming so inhumanly difficult -- we are not compilers. Subtext is a new medium in which the representation of a program is the same thing as its execution. Like a spreadsheet, a program is visible and alive, constantly executing even as it is edited. Program edits are coherent semantic transformations. The essence of

This paper presents the design philosophy of the Hyperflow visual programming language. It also gives an overview of its semantic model. The primary purpose of the language is to provide a user interface for a pen-based multimedia computer system designed for school children. Yet it is versatile enough to be used as a system programming language. The concept of visually interactive process, vip in short, is introduced as the fundamental element of the semantics. Vips communicate with each other through exchange of signals, either discrete or continuous. Each vip communicates with the user through its own interface box by displaying on the box information about the vip and by receiving information pen-scribed on the box. There are four different communication modes: mailing, posting, channeling, and broadcasting. Mailing and posting are for discrete signals and channeling and broadcasting are for continuous signals. Simple Hyperflow programs are given for the purpose of illustration, in...

Exception handling is widely regarded as a necessity in programming languages today, and almost every programming language currently used for professional software development supports some form of it. However, spreadsheet systems, which may be the most widely used type of "programming language" today in terms of number of users using it to create "programs" (spreadsheets), have traditionally had only extremely limited support for exception handling. Spreadsheet system users range from end users to professional programmers, and this wide range suggests that an approach to exception handling for spreadsheet systems needs to be compatible with the equational reasoning model of spreadsheet formulas, yet feature expressive power comparable to that found in other programming languages.