Contest too difficult

I AM writing to complain about the competition in your June issue. What annoys me most is that the amount of people entering this competition is limited to those who have a fair amount of knowledge about electronics and computers, and that must surely be a small percentage of your readers.

As this is a magazine for all Sinclair users, surely a competition which everyone could enter would be more appropriate?

Admittedly, the Spectrum is an outstanding prize but if it is so good, why not give everyone a chance of winning one?

Despite the complaint, I think your magazine is excellent, so continue the good work.

Philip Morris

There are two reasons why we decided to base the June competition on a hardware application. The previous two had been for software and we thought it better to set something for those with an interest in hardware. Second, we do not share your view that people with a knowledge of the electronics of computers comprise only a small percentage of our readership.

Character error

HAVE YOU noticed that CHR$ 7 and 135 are printed as the same character in the ZX-81 manual and that the graphics character on KEY 3 is missing?

I have found out that the missing character has the code 135 and that the one printed is wrong. The character with code 135 is =.

Mark Colson

Misprint problems

SEVERAL MONTHS ago I finally bought a ZX-81 and promptly set about mastering the manual. All went well until I reached page 129, Exercise 4, prophetically entitled "This one will drive you mad". Try as I might, every time I entered the program and tried to run it, I would be greeted with error code 5/90 or 5/150, or 5/210 if I pressed "Q".

After some thought, it occurred to me that the lines of the program the machine was trying to execute when the report codes appeared were all PRINT statements. That meant the machine was trying to execute those commands but had insufficient screen space to do so.

The next thing which occurred to me was that a SCROLL instruction had gone wrong somewhere, so I then set about jamming in extra scroll statements where I could. Finally, I found that 42 SCROLL made the program work.

When I wrote to Sinclair to point this out, the answer arrived with commendable speed to the effect that there was a printing error in the program and that line 40 should be terminated with a comma. In fact, that makes the program run much prettier than my alteration.

The point is that I have never seen in your or any other publication any reference to the error and that is curious - because 250,000 people have not noticed it, or 250,000 people have ignored it, or 250,000 people have achieved such a level of programming ability by page 129 that they thought it beneath them to draw attention to it.

The reason I am writing is to pose the question if there are other misprints of which we are unaware? At the very least, I think that it would be very user-friendly of Sinclair to mail a list of errata to all purchasers, so freeing people like myself of a good deal of head-scratching.

Finally, a good test of pocket calculator accuracy over a series of functions is to find the Sin of 45 degrees, then find the Cos, Tan, ArcTan, ArcCos and ArcSin of each successive result, hoping that it will yield the answer 45 degrees again. In my experience, Casio calculators, for example, yield an error of half a percent while Sinclair calculators yield an error of 33 percent. Try it on the ZX-81, using a program of the kind 10 INPUT A, 20 PRINT A, SIN A, 30 LET B= SIN A, 40 PRINT B, COS B and so on. Note that 45 degrees must be converted to Pi/4, as the ZX-81 works in radians, and 45 cannot be handled. Try a few values and you will be amazed and aghast alternately at the results.

M Campbell

RAM pack price falls

I AM writing about Sinclair User June, 1982. On page 5 you state that the Sinclair RAM pack has been reduced to £30. On page 10 you say the cheapest RAM pack is that of AVC Software at £32.50.

On pages 20, 42, 54 and 60, you advertise RAM packs for less than £30.

David Clifton

Searle corrects

THE JUNE issue of Sinclair User contained an article about me by Elspeth Joiner. The article was based largely on an interview conducted on April 7, 1982, prior to the launch of the Spectrum personal computer. In the article I am quoted as saying that Sinclair Research Ltd will launch another small computer this year. I was, in fact, referring to the then imminent ZX Spectrum.

Sinclair Research Ltd has no plans to announce new personal computers in 1982.

Nigel Searle, Head of Computer Division, Sinclair Research Ltd, Cambridge