Adding memory to a computer adds to the power and potential of the computer. Efficient use of the new potential often requires more advanced approaches to programming. M James and SM Gee, authors of The Art Of Programming The 1K ZX81, have written a follow-on book, not surprisingly, called The Art Of Programming The 16K ZX81 which looks at the enlarged scope of the ZX81 with a RAM pack and at programming techniques beyond those required for the unexpanded machine.

Although the ZX81 has many functions available, its capability is greatly hampered by its lack of memory. Similarly, if your only user experience has been with a 1K machine, your own programming ability, may be equally restricted. The authors have attempted to increase the reader's skill in programming now that the extra memory has provided the opportunity, a task which I think they have successfully met in this pocket-sized edition.

Chapter one is an unnecessary justification for writing the book and a wishy washy commentary on the printer and RAM pack. Chapter two looks at what extra memroy the RAM pack gives, what is stored where and how to manipulate these memory locations for better effect. Three utility programs Memory Use, Variable Use and Line Remember are included in the following chapter to provide the necessary knowledge and assistance in putting larger programs together and subsequently into operation. In the fourth chapter, there is an interlude from the more serious applications providing four good quality games programs. 'Depth Charge' a missile and target game exemplifies practical methods for moving graphics characters around the screen. The others draw to notice techniques like screen PEEKing and POKEing, scrolling and paged graphics, with simple explanations of where they might be put to good use.

Understanding fancy techniques may be fine, but it is certainly of little use unless you know how to incorporate them into your own programs. Thankfully, this wide ranging little book has taken this too into consideration and later pages deal with designing larger programs.

Equally well dealt with is sotring and recalling data from tape and methods for improving the range of the printer. Finally, to whet your appetite further after putting the RAM pack to good use, there is a chapter that introduces machine code. The information about formatting machine code routines is small but as a guide to just what is capable with machine code on a ZX81, it is complete.

The Art Of Programming The 16K ZX81 is published by Bernard Babani, written by SM Gee and M Jones, costs £2.50 and as a guide to the larger ZX81 it is an excellent complement. ISBN 0-85934-089-9.