DragonUser04_Aug83.pdf

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The independent Dragon magazine

6 0 p U S S 2 • 6 0 A u g u s t 1983

WINDOW ONANOTHER WORLD

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NEW RELEASES FOR DRAGON 32

FRANKLIN'S TOM B

Franklin's Tomb is an adventure for one player. Ca n you, a s Dan DiamOnd, sotve the rid e * o l the

Crypt o r w ill yo u t a ll p re y t o it s m ystery a s so m a n y others b e i m yo u . Franklin a Tomb com es

Complete with a 20-page fully illustrated Case ﬁle

EVEREST

Nestled on the border between Tibet and Nepal, the highest mountain in the world. Everest, Goddess

Mother o f the world, lo we rs bye and a half rmtes above sea level. I n 1953, Sir Edmund Hila ry and

Sherpa Tenzing Ncagey were the ﬁrst men to conquer the unconquerable N o w you have the chance

to Seale the summit of Eve re st Lhotse Or Nuptse. Will your attempt end in tragedy. o r wilt your name

live forever in the annals of mouniaineenng hrsSoey

7 RIDRUNNER

By the year 2190 the Earth is a barren and desolate wasteland Wit h a ll natural n3sources used op

the human ra ce s last hopes rest with a huge orbiting solar power station known a s GRID N o w the

GRID h a s been invaded b y a rape o f e vil druids from Frogfax V. rntent on the total subiugation of

Earth. To combat these drolds. an incredibly powerful and manoeuverabile ship. the Gridrunner, was

developed Yo u r mission slo p the drords and save the Earth' Gridrunner is an arcade game requmny

one toy s

Price List: Dragon Trek E9.95. Wizard War E7 95 G olf E7.95 G rand Prix

bog. (7 9 5 . Vulcan Noughts & Crosses £7.95. Games Compendium DI E7 95.

Salamander Graphics System E9.95. Super Sk ill Hangman £7.95 S t a r

Jammer E7.95. Nightﬂ ight E7.95. Frank lin s Tomb E9 95. Everest E7.95

Gridrunner E7.95

NOW AVAILABLE AT MAJOR BRANCHES

and

Send SAE for full catalogue with details of new releases.

Cheques or pos t al orders pay able to, SALAMANDER SOFT-

WARE, Dept, D, 27 Ditchling Rise. Brighton. East Sussex

BN1 40L. Tel: 0273 771942,

Ditt2

August 1983

Editor

GRAHAM CUNNINGHAM

(01-839 2449)

Software Editor

GRAHAM TAYLOR (01-839 2504)

Editorial Secretary

CAROLINE OWEN (01-930 3266)

Advertisement Manager

DAVID LAKE

Advertisement Executive

SIMON LANGSTON (01-930 3840)

Administration

THERESA LACY (01-930 3266)

Managing Editor

DUNCAN SCOT

Publishing Director

JENNY IRELAND

ISSN 0265-0177

Dragon Us er, Hobhous e Court , 1 9 Whit -

comb Street. London WC2

Published by Sunshine Books. Sc ot Press

Ltd.

Typesetting by Ches ham Press, Chesharn,

Bucks, Print ed by Eden Fis her (Sout hend)

Ltd. Southend-on-Sea, Essex.

Distributed b y S A 4 Dis t ribut ion, L o n d o n

SW9. 01-274 8611 Te l e x : 261643

©Sunshine Book s 1983

Subs c ript ions

UK 2.'8 f or 12 issues

Overseas E14 f or 12 issues

Contents

Letters

News

Advice on machine code loading, syntax

errors, wrap-around and disabling the

BREAK key — plus bad news on copyright

The latest developments in hardware and

software, including Dragon gets Mumps,

goes to the US and shows up at Earls

Court

9111111111PEPWW

SINISHINE

Towers of Brahma 2 6

A change of pace from blitzing and space

games — we invite you to solve the riddle

of the rings

Movement routines 2 9

If you've ever wanted to know how to make

objects move on the screen, we tell you —

and then incorporate the routines into an

exciting game

Clubs

This month we head west to Wareham in

Dorset. home of the Dragon 32 Users'

Club

What's in store

Cover feature

Our software reviewer John 'Scriven hits

t he adv ent ure trail this mont h, rec uperat es

An introduction to how the Dragon stores

data in its memory r e a d on if you want

to learn about machine coding

by playing chess and backgammon, and

still has t ime to visit t he arc ades

POKEing about

Shining a light

A look at how the Dragon's speed can be

increased and by how much — with a

glimps e at double the me mo r y

Dragon light pens cost less than other

mac hines ' - Cliv e Gif f ord tells y ou where

to get the best v alue

Open Ale

Compusense proﬁle 2 3

Find out who s behind those utility

We publis h y our programs : this mont h Nail

packages you're using

and thread, Brain teaser, Joy of music,

colour mixing and Dice for the gamblers

among you

Dragon Answers

Cathy gets a proposal but decides to stick

to answering technical questions

Competition Corner 5 0

Win a colour monitor donated by Statacom

and Portatel

Editorial

LAST M O N T H I T WA S c onﬁ rmed t hat Dr agon Dat a had set up a joint v ent ure wit h Tano

How to submit articles

The quality of the materiai we can publish in

Dragon User each month will, to a very great

extent, depend on t he qualit y of t he dis -

coveries that you can mak e with y our Dra-

gon, The Dragon 32 computer was launched

on to the market with a powerful version of

Basic, but with very poor documentation.

Every one of us who uses a Dragon will be

able to discover new tricks and quirks almost

every day. To help other Dragon users keep

up with the speed of the development each

of u s mu s t as s ume t hat w e ma d e t h e

discovery ﬁrst — that means writing it down

and passing it on to Others.

Articles whic h are submitted t o Dragon

User for publication should not be more than

3000 words long. All submissions should by

typed. Pleas e leav e wi d e margins and a

double space between each line, Programs

should, whenev er pos s ible, b e c omput er

printed on plain white paper and be accom-

panied by a tape of the program.

We c annot guarant ee t o ret urn ev ery

submitted article or program, so please keep

a copy. I f you want t o hav e your program

returned y o u mu s t inc lude a s t amped.

addressed envelope.

We pay for articles according to the length

and t he quality — it is wort h mak ing t hat

extra bit of effort.

Corporation of Ne w Orleans to cover Dragon sales in the US and South America (not

forgetting the Caribbean Basin, of course). At the time the American end of the venture

offered an interesting variant on the theme of " We 're going to be rich, we're going to be

rich." Its version was, admittedly, more restrained: " We are extremely excited about the

market potential in our territories for the Dragon."

Interestingly, too, it added: " We feel we have an excellent opportunity to compete

price wise in the US market," In fact, wise pricing, Or its opposite, is the name of the

game in America at the moment. Not-so-wise pricing appears to be Texas Instruments'

policy. Earlier in t he s u mme r its s hare pric e f ell af t er predic t ions of losses, mainly in t he

h o me c omput er bus ines s div is ion — where it had dropped pric es of the TI 99' 4A by $50.

But Commodore's price cuts yielded improved ﬁnancial results. The company is selling

its 64 for only $199 in the US — and offering a further W O rebate in exchange for a used

Vic20.

So, what price the Dragon 64? In this country. Dragon Data appears to be caught

between the proverbial rock and a hard place. Charging more than Commodore mig h t

be expected to damage sales. But competing with Commodore on prices might annoy 32

users considering an upgrade to 64K if this looks expensive compared to the Dragon 64.

Pric ing in t he US is equally problemat ic . P r e s u ma b l y Tex as I ns t rument s and Co mmo d -

ore did the same sums based on similar ﬁgures, but they came up with different answers

in their balance sheets.

Dragon Data and Tano appear conﬁdent that they have got the answer right. At the

moment too many factors have to be taken into account to decide how well-founded their

conﬁdence is. If a dealer's magin is higher on a Dragon than on a Commodore macnine

it's not hard to wo rk out which micro he will promote. And higher prices can be an asset.

In a marketing test, a shop once sold the same shoes at two prices, without revealing the

similarity to customers. The higher priced range sold better — perhaps Dragon Data and

Tano have been reading up the results of this particular piece of research.

August 1983 Dragon User 3

1 1

* A LIGHT PEN AND PEN DRAW PROGRAM FOR

ONLY E9.95

LIG

•

DRAW

* DRAW PICTURES DIRECTLY ON TO YOUR TV

SCREEN

* STORE UP TO EIGHT PICTURES IN COMPUTER

MEMORY

* EDIT PICTURES

* VIEW PICTURES IN HIGH OR LOW

RESOLUTION GRAPHICS

* SAVE PICTURES ON TO CASSETTE

* LOAD PICTURES FROM CASSETTE

* PROGRAM WRITTEN IN BASIC WITH REM

STATEMENTS TO HELP YOU DEVELOP YOUR

OWN PEN PROGRAMS

* PROGRAM CONTAINS FULLY

COMPREHENSIVE OPERATING INSTRUCTIONS

Ligh

Peo

PEr

Please send cheques o r postal orders (made payable t o

Accord Data Ltd) to Accord Data Ltd, Church Street, Great

Budworth, Cheshire

3138 '

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RE:LIS SIDattriT UNE f

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4 Dragon User At

This is the chance to air your views — send your tips. compliments and complaints to Letters

Page. Dragon User. Hobhouse Court. 19 Whitcomb Street, London WC2 7HF

Letters

Hence the new start address is

5000H

Martin Dunn,

London.

Lighter

work

J BURFORD (Open File, June

1983) is making hard work of his

machine code loading. His prog-

ram could have been written far

more simply as.

10FOR A = 1540 TO 1549•

READ BS

20 POKE A, VAL ( ''&H

30-NEXT

40 DATA FF. FE, DD. 01 BE 67,

OB CO, 9A. 3B

- The same technique could also

B S )

be used to enter Ian Nicholson's

(same issue) Machine Clock. Why

take the trouble t o enter &H

before each number, when the

Dragon will do it for you'

K A Blackwell,

)

Southampton.

Alittle

knowledge

WITHREFERENCE to your answer

to the query in June's edition

regarding disabling the BREAK

key, I think your answer illus-

trates the old adage that a little

knowledge can be a dangerous

thing.

The routine given uses the fact

that the run time routine in the

R does a call to 019AH (410)

which simply contains a RTS

(return from subroutine) instruc-

tion so that nothing is actually

done. Your routine increases the

return address b y four thus

bypassing the call to the -

forh e c k key" routine, thus

c BREAK

disabling the BREAK key.

The ﬁrst problem with your

routine is that you do not appear

to have taken into account the tact

that the area of memory used by

the routine already has a use and

your routine will under certain

circumstances cause a system

crash.

The memory between 015EH

(350) and 01ABH 1424) is used as

intercept vectors of three bytes

each. Your routine not only uses

the intercept locations for the run

time routine but also the intercept

for the LET routine 019DH —

019FH (413-415). Even if LET is

not used in a program its routine

is called by other routines

When this happens a call will

be made to 0190H (413) which

will result in the return address on

the stack being overwritten by

whatever value happens to be in

the D register and the system will,

on reaching a RTS instruction

lump to almost anywhere. Also

the routine relies on the fact that

the intercept of 01AOH (416) is

unchanged and s till contains a

WS instruction.

The routine its elf appears

correct bur it does ignore certain

facts. First, it not only bypasses

the call to the BREAK key routine

it also bypasses an instruction to

clean up the CC register. Second-

ly. the BREAK key routine does

more than check for the BREAK

key it also checks for SHIFT(Er

used to pause a Basic program.

The intercept vectors should be

changed only to a iump instruc-

tion, unless you are writing a two

byte routine, thus if your routine

was to be stored at 7000H then:

POKE 410,&H7E lump instruc-

tion

POKE 411.&H70 address 1s t

byte

POKE 412.8J100 address 2nd

byte

will cause the call to 019A to jump

to your routine at 7000H. The

routine must exit via a RTS in-

struction

In addition to your coding you

should add the missing instruc-

tion to clean up the ﬂags and also

add a routine t o replace the

SHIFTiu routine. I would advise

against using any of the ﬁrst 1K of

memory as this is used for sys-

tem variables, unless the exact

nature at the usage of that loca-

tion is known

WBailey,

Sunderland.

that is known as wrap-around.

Wrap-around occurs in a 16-bit

counter when o n reaching its

maximum count the next incre-

ment causes the counter to return

to zero. The offset used with the

CLOADM statement has this same

property of causing wrap-around

when the new calculated start

address exceeds the maximum

16-bit count le 65535 decimal.

In order to calculate the offset

required with the CLOADM state-

ment. ﬁrst subtract the value of

the original start address of the

program t ie the start address

from which the program was

originally saved) from the value of

the required new start address. If

the result of this calculation is

negative then add to it the value

65536 decimal in order to pro-

duce a positive offset value.

An example using hexadecimal

numbers best illustrates this tech-

nique. Assume that the original

start address at a program you

wish to load was 7000H (note the

Hsufﬁx indicates a hexadecimal

value) and assume that i t is

desired to load this program into

memory starting at 5000H•

First, subtract the old start

address from the new:

5000H

- 7000H

- 2000H

Since the result of this calculation

is negative now add to it the value

10000H tie 65536 decimal):

- 2000H

+ 10000H

E000H

Hence the required offset value

would b e E000H o r 57344

decimal.

Proof:

7000H — O riginal Star t

Address

+ E000H —CLOADM Offset

15000H — New Start Address

Note that the carry generated

from this sum is lost as the result

exceeds a 16-bit binary quantity,

ie wrap-around has occurred.

Questions

answered

RODNEYBENNETT'S line 'LIST X

to X + 10' in your June issue

causes a syntax error because the

LIST command only accepts con-

stants. not variables or express-

ions, as parameters. These con-

stants must be decimal line num-

bers.

In answer to Frank Hart. LLIST

(which is dealt with on page 132

of my copy of the manual) is the

printer equiv alent o f LIST .

DLOAD, I guess, is a call to some

other disk operating routine, not

covered in the manual because

disks hadn't been invented when

it was written.

All reserved words are stored

in ASCII format in the ROM, but

the ﬁnal character has its most

signiﬁcant bit set to 1 •• whereas

all ASCII character codes have '0'

in this position. This is commonly

used to indicate to the search

program that the current word

has ended. Try altering line 20 of

the program to read:

20 A$ = CHRS( 127 AN D

PEEK(I))

This will clear the indicator bit,

display the whole words, and

answer the query about TAB —

the hidden symbol is a left pa-

renthesis, which always accom-

panies TAB. and so is regarded as

an integral part of the word.

And if Chris Denne is reading

this: you don't need a FOR loop to

add up successive integers. Try

this

- 0 INPUT "NUMBER"; N

20 PRINT Nit(N+1)

30 GOTO 10

John M Kerr.

Glasgow

Wrapping

around

IN THE article on Topsy, in the

June issue of Dragon User. Pam

D'Arcy stated that it was impossi-

ble to use a negative offset with

the CLOADM statement. Although

this is true the same effect can be

obtained by using a technique

(1) The King

(

(—) Nightilight

—

(—) Dragon Trek

)

(2) Space War .....

(—) Graphics System

a Katerpillar Attack

(5)

Chess

(8)

k Mined Out

(—)

(9) Typing Tutor

Chart compiled by Boots

Software Top 10

Microdeal

Salamander

Wintersoft

Micradeal

No go for

renumber

ROBERT SHELDON S routine

(June) tor placing a copyright in

line 65535 does not, unfortunate-

ly, protect the line from deletion

Using RENUM. line 65535 can

be decreased below 64000 and

may then be deleted or edited as

required.

Norman Silver,

Chtslehurst.

Kent

August 1983 Dragon User 5

Salamander

Microdeal

Dragon Data

Quicksilva

Dragon Data

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