PROGRAM PITSTOP
Your Sinclair, December 1989

Me oh my, is Jonathan Davies a hero or what? Still reeling from
the trauma of Farty The Warthog's, er, untimely demise (Sob sob
waaaaargh! JD) our resident prog-jock is ... um ... here again!

Well, yuletide is almost upon us once again, and all over the country
those tacky illuminated snowmen are being dusted down and hung all
over lamp posts. City centres take on an unnatural multi-coloured glow
and Uncle Al rubs his hands in glee at the thought of all those
potential Speccy owners scribbling out their letters to Santa.

The trouble is, having got your shiny new +3 or whatever, what are you
going to do with it? Being a Pitstop reader, which puts you a cut
above the rest already, you'll fling away the free games pack almost
immediately and start searching for something a little more
stimulating. Then you'll think back, inspiration will strike and
you'll reach for your tattered copy of this ish.

There's yet another bumper bundle of code for you to digest this
month, starting with a decidedly handy pointer routine from Menno van
der Star. Not only that, there's a funny sort of wibbly thing from
Andrew Paine too which I'm sure will find itself a use somewhere. And
finally Thurstan Felstead makes a welcome (?) return.

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RED ARROW
by Menno van der Star

Well it's not, actually, it's a variety of colours, but red sounds
nicer. This routine is the work of Menno van der Star who, with a name
like that, could only come from the Netherlands. It does the mind-
bogglingly useful job of giving you a little pointer which you can
move round the screen and use to select icons, draw pictures or
anything like that. The code works under interrupt mode two, so once
you've run it the computer can get on with running your Basic program
while the pointer moves around as a "background task" (100%
computer-speak there).

Usage
Couldn't be more straightforward. Type in the Hex with, of course, the
Hexloader (check out issue 45 for more info on that), and save it.
Then reset the computer, put it into 48k mode if necessary, CLEAR
64999 and then load the code back in.

When you RANDOMIZE USR 65000, up it comes (fnurk). The arrow can be
moved around using Q, A, O and P, and M "fires". It's best if you put
the computer into some kind of a loop at this point, otherwise loads
of letters appear at the bottom of the screen. The longer you hold
down a key, the faster the arrow moves, but it never goes off the
screen.

When it comes to actually using the thing, you'll find that 65485
holds the x position of the tip of the arrow and 65486 holds they
position.

When you press M, 65487 changes from nought to one. By peeking these
addresses and getting your program to respond accordingly, you'll find
you can generate a masterpiece in minutes.

If, for some perverse reason, you want to get rid of the arrow,
RANDOMIZE USR 65006.

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WIBBLE
by Andrew Paine

I bet if you tried to count the number of times you've sat staring at
your Speccy screen and thought "I wish I could make it wibble about a
bit" you'd run out of fingers and toes in no time at all. Frustrating,
isn't it? Andrew Paine has obviously encountered this problem more
often than most, because he's actually got up and done something about
it. Wibble is the result, and it does in fact make your screen, or
just parts of it if you want, wibble about a bit.

To put the thing into operation, type in the Basic section and save it
with SAVE "WIBDEMO" LINE 190. Then, by way of the Hexloader, type in
the Hex at address 60000 and save it after the Basic. Then reload and
run. Wibbly, eh?

But it doesn't stop there. You can tweak the program to your
satisfaction by POKEing the following addresses:

60004	Number of repeats until picture is stationary.
60006	Number of frames per repeat(must be a multiple of 16).
60119	Shift coefficient (how far it wibbles).
65533	Address at top left hand corner of window.
65534	Width of window in characters (allow at least three characters
	on either side of your image).
65535	Height of window (in pixels).

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SPARKLE
by Thurstan Felstead

Lock up your livestock - he's back. Equipped with only a crayon and
low-voltage Speccy, Thurstan has somehow managed to put together
another jumble of letters and numbers which, when typed in in the right
order, produces astonishing results.

This time it's a short routine, with built-in demo, designed to add a
bit of sparkle to your screens (which is why it's called Sparkle in fact).

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The End Is Nigh
I think it's really time I went and thought about my Christmas
shopping. Trouble is, however early I start I'll still find myself
completely prezzyless on Christmas Eve. Please send your programs and
gift ideas to me, Jonathan Davies, at Program Pitstop, YS, 14 Rathbone
Place, London W1P 1DE.
