Department of Computing Science Working Paper Series

Administrative structure and responsibilities

Juris Reinfelds — Sun, 12 Sep 2010 16:32:33 PDT

With a high staff turnover and a heavy academic load the Department of Computing Science has to make an effort to provide some continuity and consistency in its administrative structure for the management of academic affairs. This paper summarizes the administrative structure of the department and the responsibilities of staff members.

On-line recognition of handprinted characters

John Collins — Sun, 12 Sep 2010 16:30:11 PDT

The project implemented an on-line handprinted character recogniser. A Bayesian decision rule was used in conjunction with selected feature transformations. Fourier transformations and transformations derived from discriminant analysis were compared. Discriminant features generally proved superior to those derived from Fourier analysis. A recognition rate of 98% was achieved with the use of the first 4 discriminant functions. The character set included numerals and arithmetic operators. The results from the current system provide a basis for constructing a practical device for data entry.

A state-driven vpe system

Peter Strazdins — Sun, 12 Sep 2010 16:27:00 PDT

This is a specification for a 'state-driven' VISIBLE PROGRAM EXECUTION (VPE) system which, given a small Pascal 'displayed program', automatically produces a VPE ~output program'. The VPE 'output program', when executed, visibly executes the 'displayed program' on a computer terminal.

Modularization: a first draft

Alfs T. Berztlss — Sun, 12 Sep 2010 16:23:10 PDT

From the very beginning of electronic computation program size has created problems. They have been both conceptual (How am I to understand this fifty page listing ?) and physical (Must recompile 2500 lines of code after every little change?). Software engineering has been our response to these problems. Two primary tools of software engineering are data abstraction and modularizatlon. and our purpose here Is to try and make them consistent with each other.

An EPROM programmer for the ET3400 expansion system

Michael J. Milway — Sun, 12 Sep 2010 16:18:20 PDT

An EPROM programmer has been constructed that can program 2716 type 2K by 8 bit and 2532 type 4K by 8 bit EPROMs. Expansion to 8K by 8 bits EPROMs is possible. The EPROM programmer is used as a peripheral device to the ET3400 Microcomputer Trainer Expansion system. Data to be programmed may be down line loaded from a host system or read in from another ROM or EPROM. The EPROM programmer software can program an EPROM, verify that programming was correct, read a ROM or EPROM, check for correct erasure and fill an area of memory with OxFF.

Inverse video for volker craig terminals

Michael J. Milway — Sun, 12 Sep 2010 16:14:24 PDT

Modifications have been made to the department's Volker Craig VC404 and VC4404 terminals 'to enable characters to be displayed in inverse video on an individual character by character basis. This feature has been put to good use in programs such as "Explain" and "Edit" where there is a need to highlight character strings. The two terminal models have different internal designs necessitating the use of different control sequences to enable and disable inverse video. The VC404 uses "control Q" to toggle between normal and inverse video while the VC4404 uses "control Q" to enable inverse video and "control O" to disable it.

Program development by inductive step wise refinement

R. Geoff Dromey — Thu, 09 Sep 2010 23:51:02 PDT

A constructive method of program development is presented. It seeks to unify two important ideas about program development. Namely that programming is a goal-oriented activity and that there should be a correspondence between data and program structures. The latter concept is seen to be extensible beyond the data processing context in which it was originally proposed. Induction provides the vehicle for program development by stepwise refinement, with the final program being constructed by application of a sequence of progressively more powerful generalizations. The design process employed guarantees the correctness of the final program provided each of the refinement steps have been correctly taken. The method is illustrated by a number of examples.

A rational pascal

Paul A. Bailes — Thu, 09 Sep 2010 23:35:37 PDT

Even though Pascal is a popular teaching language, it has the disadvantage that it imposes a variety of semantic and syntactic restrictions upon its users. An attempt is made to partially solve this problem by accepting the semantics of Pascal, but providing a less confining syntax for them. The replacement syntax encourages the expression of algorithms in a top-down manner. Implementation by preprocessing into Pascal is straightforward.

A low-cost implementation of coroutines for C

Paul A. Bailes — Thu, 09 Sep 2010 23:27:09 PDT

We identify a set of primitive operations supporting coroutines, and demonstrate their usefulness. We then address their implementation in C according to a set of criteria aimed at maintaining simplicity, and achieve a satisfactory compromise between it and effectiveness. Our package for the PDP-II under UNIX allows users of coroutines in C programs to gain access to the primitives via an included definitions file and an object library; no penalty is imposed upon non-coroutine users.

A tutorial introduction to the Unix to Univac communiation system

Cecily S. Bailes — Thu, 09 Sep 2010 23:20:25 PDT

ThIs tutorIal describes the use of the UNIX to Univac 1100 communications software. The following facilities are provided: a -transparent link- to the Univac so that a UNIX terminal may be used asa Univac termInal; the submission of batch jobs to the Univac; and file transfers between the UNIX and Univac systems.

A tutorial introduction tothe submit system

Cecily S. Bailes — Thu, 09 Sep 2010 23:10:21 PDT

An automated student programming assignment submission system is presented. Authorised tutors can define submission parameters for particular assignments. Including the setting of deadlines and the testing of submitted programs. Students can submit documentation program source and test data files. and authorised tutors can then access the collected results of the students' submissions for assessment.

A discipline for program development

R. Geoff Dromey — Thu, 09 Sep 2010 22:59:53 PDT

A constructive method of program development is presented. It is based on a simple strategy for problem decomposition that is claimed to be more supportive of goal-oriented programming than the Wirth-Dijkstra top-down refinement method. The strategy can minimize case analysis, simplify constructive program proofs, and, ensure a correspondence between program structure and data structure.

A rational pascal

Paul A. Bailes — Thu, 09 Sep 2010 22:58:32 PDT

Discussed is the way in which even though Pascal is used for teaching programming. it is unsuitable as a tool for the development of algorithms (as a human thought process) because of the burden of syntactic detail imposed upon the programmer. Consequently educators sometimes introduce a pseudo-code in which to derive ana express algorithms. Such a notation is free of any syntactic detail. but is unfortunately tree of any rigorous semantics definition, with consequent problems in using it to devise and define algorithms. An attempt is made to provide a technical solution to the problem of providing a less obtrusive syntax for Pascal semantics providing a vehicle for expression based on a set of well-defined constructs out tree at the superfluous notational detail that afflicts Pascal programs. The results ot the attempt are assessed. and consideratlon given to implementation issues.

CSP at WSS

C. A. R. Hoare — Thu, 09 Sep 2010 22:54:53 PDT

This preprint contains a copy of the visuals on Communicating Sequential Processes which were presented at the First Wollongong Summer School on the Science of Programming at Sponar's Chalet. January 31 - February 9, 1983.

A semantically-based formatting discipline for Pascal

Paul A. Bailes — Thu, 09 Sep 2010 22:52:54 PDT

The abstract (or semantic) syntax of the Pascal language IS identIfied and a linear representation for the trees so formed within tne framework of the concrete syntax for that language is imposed. The indentation seneme 50 formed. augmented with a small number of pragmaticconsiaerations. is compared with several previously proposed formatting schemes for Pascal and an example of rne use of tnls new method is given.

A screen oriented simulator for a DEC PDP-8 computer

N.A.B. Gray — Thu, 09 Sep 2010 22:51:56 PDT

This note describes a simulator for the DEC PDP-8 computer. The simulator is intended as an aid tor students starting to learn assembly language programming. It utilises the simple graphIcs capabilities of the terminals in the department's laboratories to present. on the termInal screen. a view of the operations of the simulated computer. The complete system comprises two versions at me program two simulating a PDP-8 computer and a simplified "assembler" tor preparIng students' programs for execution. There are also a number of example PDP-8 programs illustrating partiCUlar aspects of that computer.

A discipline for loop construction

R. Geoff Dromey — Thu, 09 Sep 2010 22:45:02 PDT

A discipline for loop construction is presented which is based on the concept of a well-formed postcondition. A well-formed postcondition is seen to have an implicit logical structure which is made explicit by appropriate. variable binding. This variable binding identifies the loop invariant and a determinate. Loops are then constructed by first identifying the weakest iterative mechanism capable of establishing the postcondition. Subsequent development proceeds by way of inducive stepwise refinement. This discipline for loop construction leads naturally to a scheme for classifying loop mechanisms. It also leads to a proposal for a weak loop grammar (not in principle unlike Chomsky's phrase structure grammar) which helps to make explicit semantically important components of a loop structure. The grammar is enhanced by a set of funOamental transformation rules.

QUACC - A query and reporting system for UNIX system accounting data

Nicole Cooper — Thu, 09 Sep 2010 22:33:44 PDT

This document is the technical report for an interactive screen-based query and reporting system for accounting data collected by the UNIX system on the Computing Science Perkin-Elmer computers.

ACOL - accounting information on line

Adrian Gallagher — Thu, 09 Sep 2010 22:28:55 PDT

NAME acol - accounting information on-line SYNOPSIS acol [ -a afile ] [ -bcdghpru options ] [ -f ffile ] DESCRIPTION Acol provides a method of reporting on the accounting data collected by UNIX and stored in /usr/adm/acct (see acct(5)). Output can be in either of two formats, reports or graphs. Commands can be supplied via command line arguments, however if no arguments are present, except for a -a, you will be prompted with a screen on which you can enter the commands. When the screen is used to enter the commands they will be verified as much as possible.

Introduce me to my Macintosh

Jennifer Callacott — Thu, 09 Sep 2010 22:20:49 PDT

This report is divided lnto four sessions. Session One outlines the Macintosh hardware, Session two outHnes the operating environment of the Mac. Session three describes the Macwrite software application function. Session four introduces the Macintosh Pascal environment for the creation and execution of Pascal programs. Objectives for each session are described at the beginning of each session. Operations, commands and functions are printed in a different type style so that they are easily read and noticed. The report is fashioned such that the student must begin at the beginning and build upon the skills he learns until the end is reached. Further experimentation With functions not described here is expected to be discovered by the student. The Macintosh machine has many other amazing capabBjUes other than those described here. Documentation obtained from Apple Computer Ltd. will explain these functions adequately if there is a desire to learn more.