Preface

This book arose from lectures on data representation given to First year Com- puter Science students at the University of Auckland. But then it grew as I realised that ever-more material seemed relevant, useful, or just interesting. To a large extent it rejects my own journey through computing from about 1964–2004, starting from logic design, through computer hardware, computer arithmetic and data communications into, Finally, data compression. Thus the computers that I reference are largely those with which I have at least passing experience. (There are of course many others that I have not encountered, but few of these are mentioned.) And the footnotes and asides often come from personal experience; many are distant recollections which I cannot now attribute. A comment made by one person who read this book was “This is an area that everybody thinks they know, but really nobody really knows very well”. While most elementary Computer Science books certainly describe some data representation (usually restricted to current “best practice”), and other books give great detail of specialised topics such as ?oating point, there seems to be a great gap in the middle. It is this gap, giving reasonable coverage of most data types from first principles, that I hope this book supplies. It deals mostly with data at the architectural level, with no mention of the trees, lists etc as normally covered in Data Structures courses. The main exception here is the description of text strings – characters are of little inter- est in isolation; strings are the usual entity to be manipulated and are often regarded as a data primitive. It also includes a comprehensive coverage of variable-length integer representations and of checksums, both topics which seem to have little overall coverage in the general literature.