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## A Multi-Microcomputer Based Reading Machine for the Blind

### Pattern Recognition Theory and Applications (1982-01-01) 81: 521-530 , January 01, 1982

An adaptive system for reading material printed in different fonts has been constructed using several microcomputers operating in parallel. Characters were read and identified through the extraction of point distribution patterns and geometrical features. A two-stage classifier was implemented. A very high performance has been achieved when tested on a large number of samples composed of upper and lower case letters, numerals, symbols and punctuation marks printed in several different fonts. Phonetic rules were implemented on one of the microcomputers to generate voice from a speech synthesiser. This system enables a blind person to hear what is printed on paper.

## I

### Dictionary of Information Technology (1982-01-01): 159-182 , January 01, 1982

## Shift Registers and Counter Registers

### From Hardware to Software (1982-01-01): 132-147 , January 01, 1982

It is convenient to have registers which have a built-in capability of performing operations on the bit patterns stored in them. Such operations include *shifting* and *counting*. In SDC, the ACC will be a *shift register* so that the SHR instruction of table 1.4 can be executed. The SCR will be a *counter register*; this will enable its contents to be incremented by 1 during the instruction cycle so that it contains the address of the next instruction to be executed.

## Two Alternative Definitions of Synchronic Distance

### Application and Theory of Petri Nets (1982-01-01): 52 , January 01, 1982

The purpose of this note is to present two closely related definitions of the notion of synchronic distance. We have developed these definitions because we feel that they might be easier to grasp and to work with than the original definition given in [1].

## Introduction

### The Origins of Digital Computers (1982-01-01): 1-7 , January 01, 1982

A mere chronology of inventions relating directly to the mechanisation of digital calculation starting, say, with N*apier* or P*ascal*, can give an entirely misleading view of the origins of computers. In some cases a particular step forward can be seen to have been directly influenced by knowledge of the efforts of previous pioneers, but in many cases no such evidence is readily discernable, More importantly, such a chronology tends to obscure the role played by other less directly related events, for example, improvements in technology, and changes in governmental and public attitudes, such as occurred at the onset of World War II when vast sums of money were made available for computer development [1]. A proper treatment of the development of the digital computer is therefore very much a task for an historian of science. In this book only the briefest of introductions have been provided to each of the subsequent chapters in a modest attempt to put the work described in the original accounts that form the bulk of the text into perspective.

## The Möbius Function of a Partially Ordered Set

### Ordered Sets (1982-01-01) 83: 555-581 , January 01, 1982

The history of the Möbius function has many threads, involving aspects of number theory, algebra, geometry, topology, and combinatorics. The subject received considerable focus from Rota’s by now classic paper in which the Möbius function of a partially ordered set emerged in clear view as an important object of study. On the one hand, it can be viewed as an enumerative tool, defined implicitly by the relations
$$f(x) = \sum\limits_{yx} {g(y)} {\text{ and }}g(x) = \sum\limits_{yx} {\mu (y,x)f(y)} $$
where *f* and *g* are arbitrary functions on a poset *P*. On the other hand, one can study μ for its own sake as a combinatorial invariant giving important and useful information about the structure of *P*.

These expository lectures will trace this historical development and recent progress in the theory from both of these points of view. Topics to receive special attention are these: (i)

the Möbius function as a geometric invariant, for geometric lattices and other ordered structures associated with geometries;

(ii)algebraic and homological methods;

(iii)a catalog of interesting families of partially ordered sets for which the Möbius function is known.

This paper is a brief expository account of some basic results in the theory of Möbius functions on partially ordered sets. It is not a survey, and no attempt will be made to be complete. What this paper represents is a summary, with complete proofs, of the basic results upon which the subject rests. For the most part, these are taken from Rotafs pivotal paper, “On the foundations of combinatorial theory I: The theory of Möbius functions” [Ro1], and from several papers of Crapo ([Crl], [Cr2]), in which Rota’s work was extended significantly. We have endeavored to refine and condense the proofs as much as possible, although this has also led us to abandon interesting (but less efficient) lines of development. For the reader interested in learning more, there is a substantial bibliography including many recent papers of considerable importance.

If there is a “modern era” of the Möbius function, it begins in 1964 with Rota’s paper [Rol]. One could argue, of course, that the story begins earlier: the Möbius function of elementary number theory has a rich and varied history stretching back to the last century. The inclusion-exclusion principle has its roots in combinatorial antiquity. Significant steps were taken before 1964 (e.g. by Weisner, P. Hall, Dilworth, and others) toward developing and using a theory of Möbius inversion on arbitrary partially ordered sets. However Rota’s paper marks the time at which the Möbius function emerged in clear view as a fundamental invariant, which unifies both enumerative and structural aspects of the theory of partially ordered sets. The title of [Rol] is a startling prophesy, fulfilled to a great extent by the paper itself, and also by many lines of research which continue to this day.

We hope this paper will help whet the appetite of those not yet fully acquainted with this interesting and important subject.

## Rules for program statements

### An Introduction to the PL/CV2 Programming Logic (1982-01-01) 135: 121-135 , January 01, 1982

## Prozeduren und Variable

### Pascal für Mikrocomputer (1982-01-01): 50-99 , January 01, 1982

### Zusammenfassung

In diesem Kapitel geht es für Sie darum zu lernen, wie man ein Programm in einfache Unterprogramme aufteilt, die man “*Prozeduren*” nennt und Speicheradressen im Rechner mit Namen zu versehen, in denen Daten, sogenannte “*Variable*”, gespeichert werden können.

## Information theoretic approximations for M/G/1 and G/G/1 queuing systems

### Acta Informatica (1982-04-01) 17: 43-61 , April 01, 1982

### Summary

This paper presents new results concerning the use of information theoretic inference techniques in system modeling and concerning the widespread applicability of certain simple queuing theory formulas. For the case when an *M/G*/1 queue provides a reasonable system model but when information about the service time probability density is limited to knowledge of a few moments, entropy maximization and cross-entropy minimization are used to derive information theoretic approximations for various performance distributions such as queue length, waiting time, residence time, busy period, etc. Some of these approximations are shown to reduce to exact *M/M*/1 results when *G = M*. For the case when a *G/G*/1 queue provides a reasonable system model, but when information about the arrival and service distributions is limited to the average arrival and service rates, it is shown that various well known *M/M*/1 formulas are information theoretic approximations. These results not only provide a new method for approximating the performance distributions, but they help to explain the widespread applicability of the *M/M*/1 formulas.