PCW Machine CodeLittérature English
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There seems to be an increasing interest in programming the PCWs with machine code, perhaps because only now, more than three years after the machine first appeared, is information becoming freely available on the intricacies of the PCW operating system.

This book has been written using LocoScript and printed out on the standard dot matrix printer. It shows. But on the other hand it has been written by a PCW enthusiast, and the shows too. Keys takes a rather eclectic approach to his subject which is to say that what interests him is covered in great detail, and what isn't, isn't. It's not a tutorial book for beginners, and those new to machine code won't be much enlightened.

Within the 172 pages Keys covers few of the intricacies of the Z80 processor itself but goes into a lot of detail on how to actually make things happen. There are numerous code fragments and several complete routines all with detailed explanations of how they work. This is especially true of the sections on screen access and block shifting.

If you've been wondering how to directly access the ram drive, or create and use sprites in the screen enviroment, then this is the book you've been waiting for. However it is not intended as a comprehensive guide to CP/M or to the Z80 and the author freely admits as much.

Code of practice

There are some quirks, for instance Keys clearly works from BASIC and prefers decimal numbers to Hex. This involves him in much conversion work. Another quirk is the complete absence of those utilities that make machine code programming easier: no editors, macro assemblers, relocating code or library utilities, he prefers paper and a biro. But if you need such goodies as 32 bit multiplication routines, or want to know how to calculate cosines from lookup tables, it's all here.

This is a 'How To Do It' book, with the emphasis on the practical rather than the theoretical. If you want to expand into machine code programming from BASIC this is a good place to start. For those familiar with machine code but not the PCW this book will provide many valuable insights. Equally fascinating is the insight it gives into the author's mind. Had it been written as a journey of discovery rather than pitched somewhere between a textbook and a cookbook it would have made better reading.

Keys' work is extremely useful and ring bound to lie flat while being used, but is marred by poor presentation and toe high a price; if you are seriously into programming the PCW then get it for your CP/M and machine code library.



★ PUBLISHER: Spa Associates
★ YEAR: 1989
★ AUTHOR: Michael Keys

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L'Amstrad CPC est une machine 8 bits à base d'un Z80 à 4MHz. Le premier de la gamme fut le CPC 464 en 1984, équipé d'un lecteur de cassettes intégré il se plaçait en concurrent  du Commodore C64 beaucoup plus compliqué à utiliser et plus cher. Ce fut un réel succès et sorti cette même années le CPC 664 équipé d'un lecteur de disquettes trois pouces intégré. Sa vie fut de courte durée puisqu'en 1985 il fut remplacé par le CPC 6128 qui était plus compact, plus soigné et surtout qui avait 128Ko de RAM au lieu de 64Ko.