Beginners' assistance is not appreciated

WHAT is going on at Sinclair User? I bought the October edition only to find on page 25 an article entitled A lifetime's obsession can easily be acquired, which also appeared on page 23 of the September edition and page 27 of the August edition. A very similar article also appeared on pages 50 and 51 of your May edition.

I would suggest that in pursuing this extraordinary editorial policy you are deliberately misleading those members of the public, including myself, who buy your magazine in good faith regularly, expecting to read a fresh set of articles each month and not the same stuff rehashed month after month.

The only explanation I can perceive for this bizarre situation is that the energies of your staff have been channelled virtually exclusively into the production of the supplement, Spectrum User. I would take this opportunity to remind you that the vast majority of Sinclair users are ZX-81 users and I suspect that this is also true of your readership.

By all means try to cater for Spectrum users but let it be within the format of the magazine and not in a 24-page supplement which can serve only to create a privileged minority within your readership.

M P Nadin

The reason for including the regular Starting From Scratch spot is that with sales of the ZX-81 running at many thousands a month, there is always a large number of people who are still encountering all the problems most users had when they bought their machines.

The article occupies one page which, in a total in the October edition of 39 editorial pages, is not a great deal to have to give up if it helps others to take the first steps to find how to enjoy their new machines.

As you will have noticed, in this issue we have decided to incorporate Spectrum User within the rest of the magazine. While disagreeing that the vast majority of our readers own ZX-81s, we felt that having a separate section limited our flexibility to bring you the best news on the whole range of Sinclair machines.

Voucher alternative

ANY DAY now I will be receiving my Spectrum, of which I have heard some very good reports, but there is something which I find a little puzzling - the £10 voucher which can be used in part-payment for a ZX printer or to buy a complete pack of five rolls of printer paper.

Supposing I do not want a ZX printer or the rolls; surely the compensation for the delay is being reduced by £10? Why not permit the voucher to be used for any piece of ZX equipment, like some tapes, or part payment for the 48K RAM add-on?

S Chamberlain

Sinclair Research says that alternative methods for compensation were considered but it decided against offering the voucher for future products. As it had and has no fixed launch or availability dates it was felt that it would be unfair to customers. Also at the time the offer was made there was no Spectrum software available from Sinclair.

More news from the ROM

I WOULD like to make a few points about my Spectrum ROM article in your October issue, as I have now completed its disassembly.

A RST 10 is also used to output characters to the printer and microdrives, so to be sure of screen output, place at the beginning of any routine the instructions:

LD A,02h
CALL 1601 h

If the I register contains a number between 64 and 127, picture break-up occurs. That must be something to do with the ULA.

There is a misprint in the listing - the beginning of line 30 should be 'DEF FN B$(A)...'

Andrew Pennell

Radio group still exists

I WRITE to inform your readers of the continued existence of the Sinclair Amateur Radio User Group which, despite an announcement that it will cease to function will, in fact, continue to function for the foreseeable future. SAROG, formed in 1981, was set up to provide radio amateurs with the means of sharing experience and expertise in the use of the Sinclair micros in amateur radio projects.

Achievements to date include the full implementation of Morse code transmit and receive in SLOW mode on the ZX-81 and the same functions are being sought in radio teletype. The same models are also being pursued with the Spectrum.

The group is non-commercial, non-profit - we sell nothing nor do we use advertising material. We share our information via a newsletter which usually runs to about 16 sides of A4 paper. It is hoped soon to produce it quarterly.

Membership is open to all licensed radio amateurs in the U.K. and Europe, though it is to be noted that we cannot accept members from the Americas. U.K. membership costs £5; non-U.K. residents should pay £8 in sterling only. Full payment details for non-U.K. enquirers may be had for 21RCs. All U.K. enquiries should enclose s.a.e. Telephone enquiries are not welcome.

Some countries may require extra subscription due to high airmail charges, if airmail is required. We cannot accept those with other micros.

May I say that the reason we are able to continue is in no small part due to the help obtained from some members who came to us originally from information supplied in an earlier issue of your magazine.

Paul Newman

Home learning is best

SINCLAIRVOYANCE - September - drew attention to the dangers of home education. The concluding sentence - "At the moment, however, the problems of transferring learning to the home seem too great to be surmounted" would seem to be denied by the more than 700 members of Education Otherwise, most of whom are educating their children at home - otherwise than at school.

My view of the use of computers in learning is that they are best when used as aids to developing thinking and logical skills. Logo is an excellent example. The idea of using them for the kind of quiz games which seem so popular among writers of educational software at the moment seems little better than text books.

At a recent conference of Education Otherwise, attended by about 250 adults and 100 children, a room was set aside for a demonstration of computers and their uses. I was there with two ZX-81s and met a number of people who already use a computer for home education or were thinking of doing so. It seems computers certainly have a place in home-based education.

I must confess, however, that I see one of the main advantages in home-based education as being the greater availability of adults' time in such a situation. Compared to that, computers are a poor substitute.

One other point mentioned in Sinclairvoyance was that schools are a major stage in learning social skills. Most of my friends involved in home-based education would argue that most schools encourage the wrong kind of social skills - unhealthy competitiveness being mentioned by many - and that there are plenty of other places for social contact outside school.

C W Parker

Music aid good value

IN THE October issue of Sinclair User, I feel that the article on the ZX-81 Multi-Sequencer entitled Roll over Beethoven was somewhat unfair in describing its instructions as incomprehensible. As a professional musician, I find the system easy and flexible to produce my own work and good value at £15.

Peter Hanson

Routine crashes

I HAVE owned a ZX-81 personal computer for 10 months, during which time I have had no problems with it. It was a surprise, therefore, to me that while entering machine code into a REM statement earlier this week that problems began to develop.

Until that moment, I had written considerable amounts of machine code for the computer with considerable success but it was the first time I had included the following two instructions in a routine:

126 LD a,(hl)
118 halt

The inclusion of the LD a,(hl) instruction in a REM statement holding a machine code routine resulted, on listing the statement, either in the truncating of the REM statement or the production of a flashing listing of the statement moving in a diagonal path down the screen.

Inclusion of the halt instruction in a REM statement led similarly to the truncation of the statement on listing although, in addition, that also produced a four-digit number on the line following the statement. That number, I discovered later, appeared to be dependent on the character used to fill out the REM statement in the first place.

On demonstrating the problem to staff at my local branch of W H Smith, where I purchased it, I was promptly handed a replacement. Out of curiosity, I decided to carry out the same demonstration test on the machine in the shop before taking it. To may surprise, it suffered the same problem as my original computer. Perplexed, a young assistant supplied me with five more computers to examine, all of which, on testing, had the fault.

G Mallet

We contacted Sinclair Research and the reply was that attempting to list a REM statement with code 118 and possibly 126 may cause crashing. The solution was either to avoid listing the REM or to POKE in the correct values before running the routine and POKE in dummy values afterwards.

Leap improves calendar

I WAS interested to see William Mitchell's program Calendar - Sinclair User, October - as, several years ago, I wrote such a program for my Sinclair Cambridge programmable calculator based on the same method of calculation.

There appears to be an error in the program in that it calculates the years 1800 and 1900 as being leap years, which they are not. That results in an incorrect answer being given for the months of January and February of those years - try December 31, 1799 and January 1, 1800, which will be given as a Tuesday, for both dates. The program can be corrected by:

55 IF A=0 AND B<=2 THEN LET A=1

That will have the effect of correcting the error, at line 90, of subtracting 1 for all years divisible by four without remainder.

Taking a cool approach

REGARDING the letter from Marion Stubbs in the September issue about over-heating, I had the same trouble when I used my ZX-81 without the 16K RAM pack.

The voltage from the power pack often switches to almost 12V instead of 9V so that inside the ZX-81 the voltage regulator has to deal with a greater voltage dropping - 12V to 5V instead of the 9V to 5V. That resulted in greater power dissipation, so that heat emission of the connected cooling plate rose.

As the case of the ZX-81 has a smaller ventilation hole, much of the heat will remain inside the case.

My final solution was to place a voltage regulator between the power pack and the computer so that the voltage input was reduced to the voltage input of about 8V and own the computer remains very cool.

Paul Cauwe

Families branch out

THE LETTER from L Gross in the October issue of Sinclair User attracted a great deal of interest. Gerard Fitzgibbon and D Bradburn replied that they had written programs on the subject. G.S Baker wrote that a program was in preparation.