Chris R. Jesshope

An intelligent pascal editor for a graphical oriented workstation

A Pascal syntax directed screen editor, designed to run under PNX on an ICL Perq workstation is presented. The editor (Eliot) offers a structured approach to text editing and provides complete Pascal syntax checking. The exceptional graphic capabilities of the Perq are used to good effect in providing an efficient user interface by way of a hierarchy of pop‐up menus. Using this interface, skeletal programs may be entered down to the assignment statement, or procedure call level without recourse to the keyboard, selections being made from menus using a graphics tablet and puck. Eliot encourages block structured programs with nested blocks by the use of a tree structured menu, representing the program structure. This allows for efficient movement around the program, again using the tablet and puck. Syntax checking is performed continually with errors reported and highlighted immediately for correction at will. For further error checking a variable scan option can be invoked which lists details of variable names which are not declared, or declared more than once, or declared and not used at all.

Parallel processing, the transputer and the future

Abstract Parallel processing computer systems are undergoing a revolution. The transputer, in the UK in particular, has stimulated unprecedented growth in the area of distributed parallel processing. This paper traces the history of parallel processing machines - describing the Illac V, Cray 1, and ICL DAP series - and examines the key factors that have contributed to the transputers impact. Predictions for future parallel systems embrace efficient packet switching, programming languages that allow the user to specify target-independent programs, and heterogenous system architectures.

Implementations of Load Balanced Active-Data Models of Parallel Computation

VLSI has encouraged the use of large scale parallelism in computer systems. This paper introduces an active-data model of parallelism applied to arbitrary data structures. An implementation of this model is described, and its limitations are sought. This implementation on the RPA computer system uses a fine-grain, SIMD-like, array-in-memory system, hosted by the INMOS transputer. Process or algorithmic parallelism can therefore be exploited at the top level of the system by replication of this basic unit. This synergism will be explored through the consideration of objects implementing the active-data model as a means of exploiting efficient and portable systems.

MUNAP: an unusual computer with clear implications: Baba, TMicroprogrammable parallel computers MIT Press, Cambridge, MA, USA (1987) £26.95 pp 290

The eighth addition to MIT Presss Computer Systems series in three years, this book describes work carried out at Utsunomiya University, Japan, on a microprogrammable parallel computer called MUNAP. MUNAP is a small-scale-parallel, twolevel-microcodable machine. At the microprogram level, the machine executes a common instruction stream. However, individual microinstructions may invoke different nanoprograms in each processor. At the second level of microcode (the register transfer level), the MUNAP machine is an MIMD (multiple input, multiple data) computer. The manner in which the two levels of microprogrammability interact is novel, and is described in some detail. The book is comprehensive and covers a range of interests, from architecture, implementation, through firmware engineering to applications studies. As the series preface suggests, this book should give insight into the design process of implementing computer systems architectures. The author takes the reader through the various design decisions that were reached in formulating the specification of MUNAP. At the hardware level, support is provided in the architecture for tagged data access, field handling and variable-length word access. At the system level, the prototype described comprises four processors connected by their memory buses through a shuffle exchange network, which performs intraas well as interprocessor data permutations. The applications implemented and evaluated on MUNAP include emulation, programming language processing, database systems, graphics and numeric computation. The applications considered emphasize the areas where conventional Yon Neumann architectures suffer from drawbacks, such as applications involving abstract data types or requiring tagged architectures. In particular, two new language paradigms have been studied: logic programming and object-oriented languages, in the form of PROLOG and SMALLTALK. This section occupies approximately 50% of the book and provides detailed implementation and evaluation information. In conclusion, the application implementations should be of value to mainstream computer scientists and the architecture should be of interest to computer engineers. However, the use of the word parallel in the title of the book is a little misleading, as it is really only lowlevel, functional parallelism that is exploited in any of the applications. For example, in the implementation of PROLOG, OR and AND parallelism are ignored in favour of unification parallelism (expression parallelism). This is to be expected, given the limited hardware parallelism of the machine. I would like to have seen extrapolation of the applications to a more parallel implementation of MUNAP. The book is hard bound on goodquality paper and represents reasonable value for money at £26.95. The only criticism that I have on the presentation of the book is the rather poor quality of camera-ready copy used for production. Overall this is a very well conceived book; it describes the implementation and exploitation of an unusual and powerful computer, with clear implications given the current trends towards more abstract and dynamic architectures. Its readership will be limited to engineers in research and development laboratories, and to advanced course and research students.