Your Spectrum
Issue 9, November 1984 - Letters
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I've had a bit of bad experience with a Trojan Light Pen, and I think some of your readers could benefit from my problems.
I purchased the device at the Alexandra Palace ZX Microfair early this year after seeing an impressive demonstration at the Trojan stand. I tried it as soon as I got home and, after loading successfully, tried to use the commands as shown in the instruction sheet. I couldn't get the screen instructions to work at all and, when I eventually managed to get to the Hi-res screen, positioning the pen over the letters on-screen gave no response whatsoever.
I gave the device to one of the brightest hackers we have in the sixth form at the school where I teach and, although he had more success than myself; reported that he wasn't impressed, especially with the DRAW command.
Eventually, I decided to return the device to Trojan, who made no apology for my lack of success, quoting their experience of a 12-year old girl who managed to make it work within 30 minutes. Having recently bought a new TV with a higher resolution, I settled down to try again - and this time found that I could get further. But still, the flickering cursor meant that my drawings were far from accurate.
I doubt if Trojan will take much notice of further complaints from me, but I would be interested to hear how other readers have fared with the device. I would also recommend that other potential purchasers should check out the Light Pen on a TV similar to the one they own before they part with their money.
A Brown, Leighton Buzzard

Having recently become the proud owner of a Microdrive, I though I'd let you in on some of my recent findings. On the subject of converting programs to run on the Microdrive, my first attempt was to buy and use Trans Express - a beautiful piece of software (and definitely worth having), but it does have its limitations - my success rate at getting programs on cartridge range from five to 20 percent ... and I still couldn't get my favourite series of programs (the Level 9 adventures) to work with those cunning cartridges.
My next step was to buy the Lerm MD1. After getting over the shock of having to read the instruction manual, success started to come my way - so far 100 per cent success. Level 9's Colossal Caves now loads off cartridge in 53 seconds (from power-up to first screen). So my advice is, before you buy Trans Express, check out Lerm MD1.
I also found that my cartridges tended to 'go walkies' in the general mess around my Spectrum. So I took a quick trip into WH Smith's, bought a Mini Index Box, threw away the cards and, hey presto - ten cartridges fit perfectly.
Jon McNamara, Bishop's Stortford
Is there something you're not telling us? Write to Forum, Your Spectrum, Rathbone Place, London W1P 1DE.
With reference to the article in your September issue discussing the latest model of the Spectrum, I feel I should warn all potential (and current) games designers in your readership of a possible programming difficulty with the new issue 3, mark 5.
As Simon Goodwin mentions, previous versions of the 48K Spectrum have had their memory in two separate blocks of 16K and 32K. But, as explained in my books, Supercharge Your Spectrum and Advanced Spectrum Machine Language, machine code placed in the lower 16K of the Spectrum RAM runs about 20 per cent slower than code placed in the top 32K bank. Briefly, this is due to the fact that the ULA needs to access the lower 16K to produce the TV display, whereas it leaves the other eight chips containing the top 32K alone.
Now, according to Mr Goodwin, the new machine contains both sections of memory in eight 64K chips and I think this will result in machine code running at the same lower speed - wherever it's placed in RAM. Many programmers, including myself, have in the past taken advantage of the higher speed of the top 32K - so now you know why Manic Miner and Jet Set Willy start at 32768! - and may find that their games do not run quite as fast as they used to!
Another consequence of the new issue will probably be that previously 'pure' sound effects ('whoopees' and laser blasts) will sound 'rough' due to the ULA, which just won't stop interrupting.
I must stress that at the time of writing I have not been able to obtain a '3.5' Spectrum to confirm this and would therefore be very interested to hear from anyone who has.
David Webb, Woking

['m afraid there's a slight error in the text for the article Softening Up The Hardware in issue 6 of Your Spectrum. The error was the port address assigned to the Centronics port - the diagrams were correct but the words weren't. The text said that the port address was 'DF' (that's 223 in decimal) whereas it was, in fact, '3F', which is 63 in decimal.
John Flenley, Waterlooville

Sorry about that, folks - but these things do happen. Hopefully, though, it's not too bad to correct -just alter the lines 01040, 01100 and 01260 so that the value in brackets is '63'and not '223 '.Any queries you may have on the DIY Centronics article please send to John, c/o Your Spectrum, 14 Rathbone Place, London W1P 1DE and we'll pass them on to him. Ed.

Thanks for Steven Stratford's excellent Chip Chat speechcode programs (YS issue 7) which appeared in Program Power. Unfortunately, there's an error which crept in somehow that
I have set up a Hobbit Appreciation Society to exchange hints, tips, interesting happenings, etc, with its members. Membership is free as is the monthly newsletter. Could all correspondence also include an SAE for prompt reply; members should also include as many SAEs as they want newsletters.
I look forward to hearing from you.
Nigel Foster, The Hobbit Appreciation Society, nn xxxxxxxxxxx xxx, xxxxxxxx, xxxx xxnn nxx

Help! I typed in your program Krazy Katapilla from issue 5 of Your Spectrum, but when I RUN it, all I get is 'E: OUT OF DATA, 2550:1'. Where have I gone wrong, I checked my typing and still can't find the problem, please can you explain?
Tom Jenkins, Heaton, Newcastle-Upon-Tyne

There have been a number of calls on the Helpline enquiring about Krazy Katapilla. There's nothing wrong with the listing in the magazine - as it was checked. But we do appreciate that it's very easy to miss out something or make a simple typing error, particularly in the huge data sections of the program. Your problem sounds as though you have missed out a comma, or a number in the last block of data. Re-check this and you'll probably find the cause. Troubleshootin' Pete.

Should Ian Beardsmore buy himself a new watch? Having read his Crash Theory (issues 5 and 7) in which he stated that the 64000 display didn't NEW itself for at least half an hour, I decided to check! After entering the CLEAR, the POKE, line 110 and RUN, I started timing; 29 minutes and nine seconds later I was rewarded with my Speccy NEWing itself. So how many minutes are there in Ian's half hour?
Incidentally, while PEEKing around after the NEW, I discovered that the '66' POKEd into 64001 had not been protected by the CLEAR statement as it would with a normal NEW, having been replaced by a zero. Can anyone suggest why?
Patrick Fox, Birmingham

I think you're being a little unfair about Ian's half hour, 29 minutes and nine seconds is near enough half an hour isn't it? As for your last question, the Spectrum doesn't do a normal NEW, it performs a System Reset, which has the same effect as pulling out the plug and then replacing it. Troubleshootin' Pete.

can be corrected in one of two ways.
Either change the '11984' in line 30 of the Hex loader to 12067 and enter the data as shown, or enter the Hex loader with 11987 (but on data statement 65180, there shouldn't be an '80', only three zeros). Thus, line 65180 should read:

65180! 225 201,0,0,0

I found the second method to be best, but both work well.
A Husain, Ramsgate

While on holiday in Hungary, I came across a magazine called Mickroszamitogep Magazin (Micro-Computer Magazine). (Hey, why didn't we get a snazzy title like that. Ed.) It has advertisements for various home-grown office computers (including an IBM-compatible!) and educational machines. There are technical articles on subjects such as 'The inner workings of a Basic interpreter', 'APL', and some complex 3D graphics.
A secondhand Spectrum there costs around £500, but the magazine gives a detailed review of Psion's Vu-Calc as well as several listings for the ZX81 -so there must be a few rich people around in Hungary.
There's also a lot of educational computing material in it, including a major article about computers in maths teaching. The magazine itself costs only 40p for 48 pages - and it's really packed with computing material.
You'll be pleased to hear that it's not by any means on a par with YS, especially when read through an interpreter (my father).
Johnathan Frank, Birmingham

I recently bought a copy of Hisoft's excellent Pascal Compiler for the 48K Spectrum and the increase in speed over ZX Basic is pretty difficult to believe. It's obviously not as fast as assembly language, but have you ever tried to assemble SIN(X/PI*2)+COS(Y)?
The biggest problem I've experienced is a lack of published programs in Pascal. With this in mind I am thinking of starting a Spectrum Pascal Users Group for exchange of programs, procedures and answers to problems. If any of your readers are interested in this idea, they should contact me (especially if they can help in the organisation of such a project).
Frank Hollis, nn xxxxxx xxxxxxxx, xxxxxx, xxxxx xxnn nxx

Well, that's really brilliant, isn't it!! OK, I accept your excuses about not giving your poor humble readers those luscious juicy POKEs for JSW but then, having at last printed all the info, you do it again! AARRGHH!
I dip my snout into your Cry of the Wulf article, only to find ol' Dave Nicholls overjoying himself about the fact that he's found the infinite lives POKE, etc. But do we get to know it? NO!
Ooo, you make me SEETHE, you do!
I'm not talking to my issue till it repents and gives me that POKE!
Thomas 'Erauqs' Smith, Lewisham

Nice to see that you've got around to publishing your first 100 per cent machine code game - trouble is, some of your readers might not have noticed that you've transposed two of the lines in the listing - and because you've included such an efficient checksum in the loader, they won't notice until it's too late!
On page 78 (Program Power, issue 8 of YS), you'll see the line numbers on the Hex listing start with the number 25000. Now look down to line 25184. The next line that should be input is line 25192 - the two lines 25360 and 25368 should be input after line 25352 in the next column after line 25352.
Apart from that, thanks a lot for a great game!
Daniel Mills, Hartlepool

I've just read the article about The Quill which, although being very good, has four points that I may be able to clarify for other readers.
Firstly, setting up a maze. The way I do this is to have four or five rooms allocated to the maze. Each room has a number so that you can exit from 'room 1' and return to 'room 1', and you can have exits from each room in all directions, ie, North, South, West and so on.
The way out of the maze is a little more difficult; I find it best to structure the

exits/entrances so that going N, S, E and W from any location, for instance, exits the maze. You can, of course, even have a letter for your exit code, eg, D, E, W, and then use the letter in a 'help' message.
To make a creature follow your character, you can type:

AT 10. ZERO 11. PRESENT 12. SET 14. LET 5-4

as the first entry in status table, followed by:

ZERO 11. NOTZERO 13. ABSENT 12. CREATE 12. MESSAGE "The Rat followed me"

as the second entry in status table. Finally, enter:

PRESENT 12. ZERO 5. CHANGE 25. MESSAGE "The Rat is tearing at my jugular". SET 18

as third entry in status table. SET 18 refers to another entry in the status table which causes a score turn end.
One thing that you didn't mention in the review was how to use BRIGHT and FLASH.

E MODE Cap Shift 9 (FLASH on)
E MODE Cap Shift 8 (FLASH off)

I'm not sure just what you mean by 'if A is true or if B is true then move an object from one location to another', but if you have to collect a certain item to complete an adventure, a good way is to
'hide' the object and then create it at a location that would have already been discounted, as in do something in location 100 which would create a 'gun' in location 5. You could do it by entering the following in the event table:


Tony Bryne, Bolton, Lancashire

I though I'd write to you and point out some interesting things you seem to have missed in your articles on Jet Set Willy.
Firstly, it was suggested that you need to get the invisible object in the First Landing. You don't. The invisible object which is actually lodged in the wall, is almost certainly another bug in the program. I've heard that you can reach it by jumping off the 39th step of the ladder (could this be a tie-in with the famous book The 39 Steps?) but I've not managed to get the blasted thing yet! Perhaps someone out there has managed it?
You're right in thinking that the room called Nomen Luni is a take-off of Imagine's Zzoom game - in Latin, Nomen Lundi can be roughly translated as 'The name of the Game', Imagine's old catchline. But there's more to this than meets the eye. If you look at the central graphics blocks in this room, you wouldn't be blamed for thinking they gave the impression of the tail end of an aircraft. Now look at the room below (Under The Roof) - can you make out what could be the front
end of the plane? Hey presto ... the joke is that a plane, probably from Imagine's Zzoom, has crashed into the top of of Willy's mansion.
I do admit to being one of those poor souls who, having read the Jet Set Loony letter in issue 7's Forum, waited six hours for the raft to appear. Well, I thought it was a joke at the time, but you can never be too sure. You also made a bit of a mess of your WRITETYPER chart by saying that Nomen Luni, The Wine Cellar, The Watch Tower and The Tool Shed can be reached using this method - they can't! You're forgiven this time, but consider your knuckles rapped.
Oh, by the way, my Speccy does prefer your Top 20 chart!
David Bailey, Mosley, Birmingham

I just thought I'd write to say thanks for all the programming tips I managed to eke out of Troubleshootin' Pete at the last ZX Microfair back in early September. Unfortunately I didn't have enough money on me at the time to buy one of your T-shirts ... but if you could tell me when the next fair is being held, I'll be there, cash in hand.
I was a bit disappointed not to be able to buy back issues 2 and 3 of Your Spectrum, but was more than pleased to get a sneak preview of YS MegaBasic. When's it going to be available?
Stuart Cooper, Andover

Well, to kick off we'll certainly be making an appearance at the next ZX Microfair - and that's being held at Alexandra Palace on 17-18th November. YS MegaBasic, for all Mike's last-minute additions, is now finished - all we've got to sort out now is the manual to go with it. Ed.
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