THE TROJAN (WORK) HORSE

Having reviewed a software oriented drawing program in the last issue of the magazine (PAINTBOX from Print 'n' Plotter), it seemed irresistible to take a closer look at one of those trendy light pens which supposedly turn your TV screen into a versatile drawing board.

The Trojan light pen comes neatly packaged in an ex-VHS plastic cassette box containing the magic wand, which could easily be mistaken for one of those promotional biros (it even includes address and telephone number) if it weren't for the protruding cable terminating into a battery clip connector and plug, a 9V PP3 battery, the utility program cassette and the instruction leaflet. The program is loaded in the usual way and prompts you after auto-running. The cassette recorder plug (EAR) is removed from the Spectrum and swapped with the light pen plug. The battery connector is clipped onto the PP3 battery. The fun may begin.

The light pen provides two independent functions. Its first use is as a fast menu pointer, enabling the computer operator to make a selection of available options just by pointing the pen at the specified line position on the TV screen. The program explains in detail how to incorporate this facility into your own programs. Required is a 200 byte long machine code routine which has to be copied and saved. This routine is accessed by two basic programs: One required for the calibration of the light pen to the individual TV set and the menu selection program, which returns the line number in form of a variable PL. The selection works every time and is reliable and fast. Only criticism is the fact that the machine code routine seems to be not relocatable and must therefore be saved in memory location 59400:

SAVE "mc" CODE 59400,200

Its second use is as a high resolution drawing pen. After selecting HIRES DRAW you are confronted with a simple pen alignment routine which gives way to a menu line display. To select a function you just align up the pen with the letter or the blank space on the right hand side and press key 1. A white cursor will travel to the point selected and the option is selected.

The menu line incorporates the following functions:

M - Move the main cursor. Once selected the program prompts you to position the pen in the desired position and to press 1.

S - Secondary cursor for line, box and circle routines.

B - Box with M and S as opposing corners.

CO - Copy screen to printer.

C - Circle with centre point M and radius ABS (M-S).

D - Draw. After selection position pen at desired starting point and press 1. A flashing cursor controls your writing speed: Do not move pen outside flashing cursor area or the line draw facility will not be able to follow the pen movement.

CR - Print characters with M as starting point.

E - Erase last action.

F - Fill area designated by M. Upon selection a colour menu will appear on the screen.

I - ink colour selection.

L - Draws line from M to S.

N - New clears the screen to the current paper colour.

P - Paper colour selection.

T - Saving or loading screen content.

The light pen performed satisfactorily with all functions, but it was found to be very sensitive to the light conditions: The TV brightness had to be adjusted for optimum results and the TV set not exposed to any glaring sunlight. The draw facility suffers from its usual setback with light pens of not being able to locate the writing position accurately enough for high resolution drawings and the drawing of straight lines in this mode requires a lot of practice and skill. Paper colour selection allows for instant colour switching, but also creates the usual confounding problem caused by the character mapped attribute resolution. Ink and paper colour will clash if not worked out within the confines of the attribute boundaries. The colour fill facility displayed the usual speed, but appeared never to crash even if the area to be filled wasn't 'airtight': the routine would escape from the leak and fill the entire surrounding area and give a triumphant bleep of approval upon completion much to the dismay of the screen designer. Using erase however clears up this mess and gives you a second chance.

Obviously the light pen has its limitations for freehand drawing due to the inaccuracy of positioning the pen on a pixel level, but then no one should expect to be able to draw to such a high resolution on the curved TV screen at an uncomfortable angle and with possible alignment errors. It is left to the individual to accept this limitation or to forfeit the freehand drawing for a cursor controlled drawing routine. Certainly the menu selection facility is very elegant and can obviously be incorporated into one's own programs.

For the ultimate professional screen creations it is still necessary to revert to the primitive paper grid pad design where the original artwork has to be simplified and coaxed into the confines of the pixel and attributes grid of the Spectrum and input via binary or decimal code direct into the screen memory area. The light pen certainly is a lot more fun to handle and should at least convert your TV screen into an amusing and versatile sketch pad.

SHEDDING LIGHT

Spectrum light pens have never really caught on. Until now most of the offerings have been wildly inaccurate or have flickered badly in use. The new Cadmaster from Trojan goes a long way toward resolving these problems.

The main thing is that it works well. The drawing program, which is supplied with it, doesn't feature the whizz-bang, pull-down menus of the new Art Studio type of program, but it is more than good enough to produce some very acceptable results.

The other advantage over Art Studio and a mouse is the price - £19.95. At less than a third of the price of the Art Studio package more people will be able to afford it.

Using the pen is very simple, just point and shoot. On loading a menu screen is displayed, from this you can select with the pen the type of line you want to draw - thin, medium, thick, dotted, spray can or two types of quill. Various options are then available to draw freehand, lines, boxes, circles etc with the added advantage that the position can be fine-tuned using the cursor keys.

Areas can be filled, albeit painfully slowly, in one of eight patterns, and there is a useful copy facility which allows you to to select part of the screen and to redraw it on one of four sizes. The finished masterpiece can be saved to tape or microdrive.

The Cadmaster has a few disadvantages. Most operations require you to point and then press a key, which may be an awkward manoeuvre for some people. The pen also needs a PP3 battery to power it and though it will last over a year it is one more thing to remember.

Overall, a commendable effort and one which should make Cadmaster the top Spectrum light pen.

Trojan Products, 166 Derlwyn, Dunvant, Swansea SA2 7PF. Tel: 0792-205491.

THE TROJAN PEN

Carol Brooksbank puts pen to screen with the Trojan Light Pen.

Trojan Products
£14.95

If you always thought of a light pen as being attached to its own interface which plugs into the peripheral port, this one will be a surprise. The twin wires from the pen separate at the end. One has a miniature jack plug attached, and the other a connector plug for a PP3 battery. You load the software supplied, remove the 'ear' plug from the Spectrum and plug the pen in there. The battery simply hangs around on the end of the wire as you work. To be honest, it looks a bit Heath Robinson, and I have to put a question mark over the arrangement's reliability. The model we had to test started working intermittently after a couple of hours, but you could get it going again by pressing the connector to the battery or jiggling the wire.

Perhaps it was just a poor connection on this particular instrument and not a symptom of an arrangement which puts too much strain on a not very strong connector. I hope so, because in other respects this is a very good light pen.

THE SOFTWARE

When the software loads, the menu appears and a light touch of the pen on the box alongside an option selects the one you want. There are three thicknesses of normal pen and two of italic, plus a dotted line and an airbrush. You select the ink colour direct from the main menu, but to select paper colour, you touch the pen alongside the colour, and then select the 'New' option which gives a choice of clearing the screen or returning. Either option takes you back to the main menu to choose the ink colour, but the second preserves your current artwork. You then select the drawing mode; freehand, circle, box, line, triangle, or ray, and you will go straight to the drawing screen.

Freehand drawing is where a light pen scores over most software graphics packages, because you have control over the speed. With the Trojan you place the pen over the spot where you want to start and press '1' or 'space'. The key must be held down while you draw so your computer must be quite close to the screen. I found that you need to work fairly slowly or you run ahead of the cursor and it is almost impossible to return the pen to the exact spot to continue a line once you have broken it. The geometric options, box, triangle etc. are easier to position exactly. You place the pen where you want the start of a line, the first corner of a shape or the centre of a circle to be, press the key, and a one pixel cursor appears. Its position is given at the bottom of the screen in x,y co-ordinates and line and column numbers, and you can use the arrow keys to move it. This can be repeated with the circle circumference or the other corners of a shape so you can position it exactly.

OPTIONS

The Fill option is efficient, but very slow, almost like a BASIC fill. You have seven textures and solid colour to choose from and the current ink colour is used. If you choose a texture, it is filled first in solid colour and there is then a pause long enough to make you think you chose the wrong option before the texture appears.

There is a Copy option, which offers a choice of small (which turns out to be the same size as the original), large, 2x height and 2x width. You place a box round the area to be copied, select the size and mark the bottom left hand corner of the new position. Again, the position is shown and the arrow keys can be used to adjust. This option is especially useful for varying the appearance of text, because the text option only offers the standard Spectrum typeface.

If you need to erase, the E key will remove the last line or shape drawn. The erase option will take out everything drawn during the last option chosen, and the window option allows you to clear a selected portion of the screen, or you can clear the whole screen. Your artwork can be saved and loaded on tape or Microdrive, and the pen software can also be transferred to Microdrive. I suspect that the BASIC can be altered to use the pen with Wafadrive, and the handbook also gives a sample program to allow you to incorporate the pen operation into your own programs.

You would not expect a light pen to be as sophisticated as the software graphics packages available, but although its options are limited, it is more accurate than I expected it to be. The ability to position lines and shapes with pixel precision is certainly useful. If you want to be the Rembrandt of the small screen you would probably use it to add the freehand drawing and stick to a graphics program for textures, colours and detailed work. But if you want basic drawing and colour facilities then this could be for you, and, above all, it is fun to use.

RAGE HARD!

You wanna know what's hardest in hardware? Once again YS whips out the magic screwdriver in our first hardware round up of '88.

It's been ages since we did a really ripping hardware spread, so we thought it was about time. After a bit of barking at Phil Snout to get his screwdriver out and look at these beasts, we've pulled together a positive cornucopia of hoopy hardware and super software, to turn even the most soft-boiled trainspotter into a hard-boiled egghead.

The star of our show is Miles Gordon Technology's Plus D disk interface, the only real alternative for tape users to upgrade to a +3, from the designers of the Disciple. Check out the review further on.

Other contenders for the hardware crown are the Multiface family from Romantic Robot, the plastic pal who's fun to be with; a couple of wacky Multiplugs for those of you who work all your household appliances from one socket; an aerial switch so you can plug all your computers, game consoles and videos into your telly at the same time; and Computer Cupboard's nifty little Trojan Light Pen for you to scribble on your screen. Worra lorra lorra stuff.

As well as all this hardware, we've got a brain-boggling selection of the most fascinating hardware-based software. So, let's cut the babbling and launch into the reviews.

6. Trojan Light Pen
Computer Cupboard
£19.95

And finally, if you want to do professional Computer Aided Design on your Speccy, why not buy a Trojan Light Pen? When you buy the Cadmaster graphics system, you get this pen shaped device, which allows you to draw straight onto the screen. This can be very handy if you are quite good at drawing with a pen, but not so hot with a mouse or joystick. With this package you can do freehand drawing, boxes, circles, lines, triangles and rays. You can choose line thicknesses, quills, brushes and text styles, copy, paste, fill with patterns, wash, colour and dump to printers to your heart's content. The program is now compatible with all flavours of Spectrum, from Issue One wubber keyboards, to the new +3 (for £23.95), and is also compatible with microdrives and other media that use that format. It's remarkably accurate, and doesn't suffer from the wristache and slap/rattle sound effects you usually get from using Spectrum mice. The biggest recommendation of the product is that it's British and so all technical backup is available from a telephone number printed on the pen itself.

In summing up, it's nice to see so many good British products in this hardware lineup. There's not many computers you could say that of, and fewer that could match the quality and design of the peripherals represented here.

HARDWARE WORLD

With ever-increasing amounts of peripherals available for Sinclair computers, users are finding it more and more difficult to know what to buy. We present a buyer's guide to joysticks, keyboard and printers and review the best of the rest from the 1984 add-on market.

The last year has brought about a vast change in the sort of add-ons available for the Sinclair machines. Many are technically brilliant while some would have made Heath Robinson blush. There are few add-ons still being produced for the ZX81, with even fewer new ones, but there has been an avalanche of Spectrum designs, and the start of what promises to be an interesting range for the QL.

The most popular areas of interest - printers, joysticks and keyboards - are dealt with in separate sections but there have been some very innovative designs produced in other areas.

TROJAN LIGHT PEN

If you prefer a more immediate means of putting graphics on the screen then the light pen from Trojan Products may be the answer. The pen is supplied with driving software on tape which allows you to draw pictures or to choose from a menu.

Once the software has loaded the pen simply plugs into the EAR socket of the Spectrum, it takes its power from a PP3 battery that is also supplied. On screen you are given the option of drawing or instructions. The instructions show how to use the pen and also how to modify it to use in your own programs as a menu chooser. All that needs is about 20 lines of Basic and 200 bytes of machine code, both of which are given. When using it in that way the code gives a number that corresponds to the line number to which the pen is pointing. In that way it is easy to pick from a list of options.

The drawing program has two movable points and by using these you can draw lines, circles and boxes, fill areas with colour or even draw freehand. Other options allow you to load and save pictures, change colours, insert characters or copy the screen to a Sinclair printer. The pen works well and is easy to use, overall a well thought out product.

Light Pen, £17.25 inc. VAT and p&p, from Trojan Products, 166 Derlwyn, Dunvant, Swansea SA2 7PF.