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SYNTAX ZX80' 

A PUBLICATION OF THE HARVARD GROUP 


VOL. 3 NO. 5 ISSN 0273-2696 MAY, 1982 


IN THIS ISSUE 


Important Notice.17 

4K Programs 

IC Inventory.18 

8K Programs 

ZX81 Intro.17 

Beginners Columns 

BASIC-Inkey$.8 

ML-Register/Register.16 

Classified Ads.20 

Dear Editor.10 

FORTH on ZX8l. 9 

Hardware Projects 

Memory Decoding.5 

Problem-Solvers.6 

2K Conversion.14 

Logic Chip Failure.4 

Microsync Speaks.14 

News, New Products..1,2,4 
Numbers Held Inexactly..3 

Program Corrections.2 

Program Improvements.... 2 


Removing ICs Cheaply...20 
Software Review 

New England Software.19 

Subscription Info.23 

Tips and Hints 

Hardware.2,3,18,19 

Software.17 

Users' Groups.2 


Index of Advertisers 


Bani-Tech.3 

LJH Enterprises.17 

Kopak Creations.16 

Memotech Corp.7 

S&S Co.15 

Sinclair Research... 1 2,1 3 

Softsync.3,11 

Zeta Software.8 


Bindaii- inaa 


Timex, the watch company that has always 
built Sinclair computers, will market and 
distribute Sinclair-based products in North 
and Central America and the Carribean 
beginning this year. Note the new name— 
Timex-Sinclair 1000. This computer is a 
virtual twin to the ZX81, except for an extra 
IK RAM under the hood (2K total). 

Watch for these other changes: 

Price —TS 1000 will sell for $99.95 
assembled. There will be no more kits. 16K 
RAM packs will go for $49.95. 

Availability —Expect computers, software, and 
peripherals from Timex to be in greater 
supply than from Sinclair. According to the 
agreement with Sinclair, Timex must meet 
certain production levels (about 3x current 
level). You will be able to buy computers, 
etc., at Timex' 100,000 retail outlets, 
including drug and department stores. 

Other Products —Timex just announced 
availability of two new products for 4th 
quarter 1982: direct connect modem ($99.95) 
and printer ($99.95). The printer shown at a 
recent press conference looked identical to 
Sinclair's UK ZX printer, although we expect 
the shielding is improved to satisfy the FCC. 
The modem will allow TS1000 and ZX'8l users to 
access any phone-up data base. 

Additionally, Timex plans to offer 25-30 
assorted educational and business software 
packages in July 1982, from $9.95-$19.95. 

According to Timex Product Manager Bill 
Skyrme, Timex is very interested in customer 
support. The TS 1000 will come with a manual 
for beginning BASIC programmers. Timex will 
continue Sinclair's 90-day warranty policy. 
Service will probably be handled through 
Timex' Little Rock, AR, facility, where 
watches are repaired in 24 hours. We expect 
Timex to maintain this level of service to 
their computer customers. 


Return your white renewal 
card early for free 
SYNTAX magazine binder. 


1 




























SYNTAX ERRORS: Walter West reports 
that Phone Number Generator 
(Feb.82) gives only 729 combina¬ 
tions as printed. Change line 110 
to 110 NEXT Z to get all 218?. 

PROGRAM IMPROVEMENTS 

William Wentz of Rio Rancho, 
NM, sent this improvement to Frank 
O'Hara's Program 1 (from his 
articles on Numbers Held Inexactly, 
Mar. & Apr.82). He says that on 
ZX8ls with 3.25K of memory or less, 
the variable VARS in line 20 is not 
constant, but keeps moving up as 
the display file (screen) is used. 
To improve the program for any 
memory size, change these lines: 

15 FOR J=1 TO 5 
30 LET IrV+J 
50 NEXT J 

NEW PRODUCT ANNOUNCEMENTS 

F/22 Press now offers Dark- 
star, a program to solve problems 
for photographers in the dark-room. 
You need a ZX81 with 16K RAM. The 
program chooses exposure and 
processing times for both black and 
white and color work. Darkstar 
tape and documentation, $99.95. 

For free info, contact Robert 
Martin, F/22 Press, P.O. Box 141, 
Leonia, NJ 07605, 201/568-6250. 

RKL Systems of Leominster, MA, 
offers 16K RAM (expandable to 32K), 
32K RAM, and single and double 
joysticks for ZX80/8ls. Units are 
fully assembled and tested. Joy¬ 
sticks come with directions for 
machine code programs using joy¬ 
stick. Prices: 16K RAM—79.95; 

32K RAM—149.95; single joystick— 
69.95; double—89.95; 16K to 32K 
upgrade—79.95. Special prices on 
package deals. RKL Systems, P.O. 
Box 515, Leominster, MA 01453. 

Memotech Corp., Oxford, UK, 
now sells their $179.95 64K RAM 
pack in the US directly and through 
distributors. It plugs directly 


into the computer and runs off the 
existing power supply. It provides 
up to 15K of RAM for BASIC programs 
with 32K left for arrays and vari¬ 
ables. Or you can cut back the 
BASIC and fill up to 45K with 
arrays. Another 8K can be used for 
machine code or data without being 
affected by NEW and RUN commands. 

They also plan a 16K RAM pack, 
high resolution graphics pack, 
digitising pad, and RS232 and Cen¬ 
tronics interface. Memotech Corp., 
7550 Westyale Ave., Suite 220, 
Denver, CO 80227, 303/986-0016. 

USERS' GROUPS 

Here's this month's list of 
new ZX users' groups. Send us word 
of your group and we'll send local 
users to you. To locate a group in 
your area, send us a SASE and we'll 
tell you what we know.—AZ 

Sacramento, CA: Contact William 
Madden, PO Box 8201, Sacramento, CA 
95818, 916/444-6780. 

North Dakota: Contact K. Allen 
Ward and Lonnie Misner, 520 Tulane 
#205, Grand Forks, ND, 58201 . 

St. Paul, MN: Contact Tom 
Lindquist, 1740 Beechwood Ave., St. 
Paul, MN 55116. 

Indianapolis, IN: Contact Andrew 
Thomas, 2804 E. 55th PI., Suite Q, 
Indianapolis, IN 46220. 

Memphis, TN: Contact Jimmie 
Barker, 3791 Barron Ave., Memphis, 
TN 38111, 901/327-2158. 

Need fast ZX80/81 service? Jim 
Burliegh of Dover, DE, reports that 
National Electronics III fixed his 
partially-assembled ZX8l kit for 
$24.95 (2.5 hours work plus ship¬ 
ping). Door-to-door by UPS took 8 
days. National Electronics III, 
10425 Kingston Pike, Concord, TN 
37922, 615/690-8927, Jeff Thompson, 
manager. 


2 


NUMBERS HELD INEXACTLY ON THE ZX81 
(Part 3 of Dr. O'Hara’s article) 


What is the largest integer 
a ZX8l holds exactly? The manual 
is wrong in saying that 2^^ is the 
largest. The largest is really 

ie., this 39-digit num¬ 
ber: 1701411834208551504745551 

34919112130560. Surprised? 

The manual is trying to say 
that every integer up to and 
including 2^^—not just 2^^-1—can 
be held exactly on the ZX81. More¬ 
over, 2^^ is the largest integer 
for which this is true^ But every 
even integer between 2^^ and 
every multiple of 4 between 2^^ and 
2^^, and in general, each multiple 
of 2*^ between 2‘^and for n = 0, 

1, 2,...94 can be held ex a c 11 y. 

And every multinle of 2^^ up to and 
including can be held 

exactly as well. 2'^'-2^^ is held 
as 255,127,255,255,255 and you 
can't squeeze another bit into 
that; the one spare is needed for 
the sign. Because of overflow and 
another ZX81 oddity, you may have 
difficulty in getting this number 
into Program 1 (SYNTAX Mar.& 

Apr.82). This works: 
2*(2**126-2**95+2**94) 

But what of printing ? 2^^+2 
can be printed exactly: PRINT 
2**32+2 (gives 4294967300). Armed 
with this information, enter: 

PRINT "42";2**32+2-42E8 This gives 
4294967298, an exact result. But 
2^^ (17592186044416) can't be 
printed by this method, as 175921E8 
is not divisible hy 2'^. 

In theory, 2^’ could be so 
printed, but a bit is lost in sub¬ 
traction on a right shift and is 
not retrieved. The largest power 
of 2 for which it works is 2^". 

PRINT 2**39 gives 549755810000 
and PRINT "5497'';2**39-5497E8 gives 
the exact result 549755813888. 

Moral: Don't believe everything 

you read in manuals! Things can be 
better, as well as, worse. 

Frank O'Hara, Surbiton, UK 

3 




CUBE 

A scientific approach to solving the 
Cube. This program allows you to set up and move 
the Cube in any configuration, gives you a choice of 
displays -- two dimensional, three dimensional and 
flat -- and remembers every move. 

I6K $14.95 

THE CHECK BOOK— 

Get rid of the draw full of old checks^ 
and end the monthly hassle of checkbook balancing with THE 
CHECK BOOK. This personal or business checking account 
program stores up to 250 transactions on a single program. Over 
3600 transactions can be permanently stored on a single cassette. 
THE CHECK BOOK provides all transaction information and memos 
and will sort by date, latest transactions or alphabetically. 

I6K $14.95 


BACKGAMMON 


This classic game of skill and luck has 
been transformed into an exciting ZX81 game using fast and 
efficient machine code and detailed graphics. Backgammon has a 
choice of four levels of skill and features screen displayed rolling 
diceand doubling cube. 16K $14 95 


CYBORG WARS' 


Rule your own country on a small 
asteroid in our galaxy. You are provided with secret reports of 
resources like population figures, stockpiled arms and rations and 
must utilize your Breeders, Farmers, Workers and Soldiers 
effectively. If you do you may take over the entire asteroid. If you 
don’t you’ll be faced with insurrection. Play against the computer or 


VU-CALC 


Turn your ZX81 into an immensely 
powerful analysis chart. VU-CALC constructs, generates and 
calculates large tables for such diverse applications as financial 
analysis, budget sheets and projections. Using a choice of grids and 
formulas you can quickly and easily set up an entire business or 
household financial management program. ^ g|^ g gg 

" “ "pLUriW^TlORT ScaT PROGRAMS “ " 

WRITE FOR FREE CATALOG 

Please send me: 

_copies of CUBE @ $14.95 ea 

_copies of BACKGAMMON @ $14.95 ea 

►_copies of THE CHECK BOOK @ $14.95 ea 

_copies of CYBORG WAR$ @ $14.95 ea 

_copies of VU-CALC @ $1,9.95 ea 

Add $1.50 shipping and handling. 

New York residents add sales tax. 

SEND CHECK OR MONEY ORDER TO: 

StJFTSYIVQUMC. 

PQ Box 480 Murray Hill Station. New'ibrk.N.Y 10156 

NAME_ 

ADDRESS_ 

CITY_ 


STATE/ZIP 




SINCLAIR UK UNVEILS NEW COMPUTER 

After much speculation about 
Clive Sinclair's "ZX82," few were 
prepared for his latest computer, 
announced in London in late April. 
Not the ZX82, but the SPECTRUM. 
Besides the new machine, Sinclair 
announced a reported 100K Micro¬ 
drive (3" floppy) for the end of 
1982. They dropped their UK 16K 
RAM price by £20, but raised the UK 
printer price to £59.95. Sinclair 
US won't know if their RAM prices 
will drop until late May. 

The 8x5x1" Spectrum machine is 
memory-mapped and comes with 16K 
ROM and 16K or 48K RAM on board 
(16K is upgradeable to 48K with an 
internal expansion board). It uses 
a Z80A processor at 3.5 MHz. No 
built-in flat screen TV yet. The 
new computer offers 8 foreground 
and 8 background colors and 10 
octaves of sound through an inter¬ 
nal loudspeaker. The color display 
is also memory-mapped and gives 
normal or extra brightness and 
flashing or steady mode. 

Technically, the new machine 
is not incompatible with ZX8ls, but 
Spectrum uses a different, faster 
(1500 baud) cassette interface, so 
you cannot directly load ZX8l 
tapes. According to Sinclair, 

"ZX8l programs may be typed into 
the Spectrum with minor changes." 
The Spectrum will work with the ZX 
printer, but not with Sinclair's 
16K RAM pack. But it includes an 
RS232 interface, so hooking up 
other printers should be possible. 
Also, Sinclair said Spectrum "may 
be rendered teletext compatible." 

The ZX8l's 8K ROM is a subset 
of the new 16K ROM, so the 16K ROM 
includes all features of the 8K 
ROM, plus up to 52 user-defined 
functions. Single keys control all 
BASIC commands and functions, 16 
graphics characters, 20 color codes 
and 21 user-definable graphics 
characters. The Spectrum also has 
a full-size 40 moving-key ASCII 
calculator-type keyboard with auto¬ 


repeat, and full upper/lower case. 

SLOW and FAST are no more; the 
Spectrum operates at the FAST mode 
speed, but with a steady display. 

It also has a VERIFY feature, 
enabling you to check complete 
storage of data and MERGE, which 
combines programs in memory with 
those on cassette. Other new 
features include multistatement 
lines, READ-DATA-RESTORE functions, 
and a real-time clock. 

Great, but what about the 
important details? At first, 
Sinclair will sell the Spectrum by 
mail order in the UK only. Price: 
£125 for 16K RAM and £175 for 48K 
RAM. The optional 16 to 48K RAM 
upgrade will be £60. Don't expect 
to see the Spectrum machine in 
North America until around December 
1982 , when Timex will presumably 
handle it. US prices are not set, 
but at press time the British pound 
was worth about $1.70 US. 

Sinclair also announced 26 new 
ZX 8 I software packages developed by 
ICL and Psion in England and avail¬ 
able in the UK in May. The pack¬ 
ages include record keeping, games, 
and educational tapes. Most use 
16K RAM. Expect these to be 
available in the US in late May. 

LOGIC CHIP FAILURE SYMPTOMS 

Milton Halpern of Plainview, 
NY, deduced that his ZX81 logic 
chip (ICl) had failed from the key¬ 
board line and diode matrix. 

Here's a chart of the symptoms: 

KBD DIODE NUMBER 

1 2 3 4 5 6 7 8 

0 -------- 

1 2 W 9 S 0 Z L . 

23E8DIXKM 

45R6GYVHB 

Chart shows result of jumper 
contact from KBD line to diode 
number. "-" means oscillation or 
blank screen. His K cursor was 
normal at the start. He got a new 
logic chip from Sinclair and now 
the ZX81 works fine. 


4 




MEMORY DECODING ABOVE 16K 

Sinclair made the ZX81 RAM 
easy to decode up to 16K, but you 
may want to add memory beyond this 
point. To add more than 16K memory 
to your ZX80/81, you must do more 
than just: 

aTs and Iv\ and aTs = ROM CS 

You’ll also need to account for the 
behavior of the display file. 

If you decode your 1st 16K 
block with A14=1 and A15=0, the 
system crashes. ZX computers need 
the display file active for dis¬ 
play, and the 8K ROM makes A15 high 
during display. You can use the 
relation: 

A14 AND (Ml OR rr5)=RAM CS 0-16K 
To get the second 16K block use; 

aT4 and A15=RAM CS 16-32K 
Get the 3rd 16K block using: 


—BANI-TECH 

Software of the Month Club 

Get the most from your ZX81 with 16K, use it to 
ifs full potential, while building an impressive in¬ 
ventory of software. Receive twelve Hsted programs— 
one a month. Programs like Income Tax Recording, 
Auto Maintenance, Household Expenses, Price of 
Gold Forecasting, Diet Planning, Scrooge’s Christmas 
Gift and Card List and many, many more for the 
incredibly low price of just $19.95 per year. Save 
your valuable time and get down to basics! 

Make checks payable to BANI-TECH 
P.O.Box 1568 
Princeton, N.J. 08540 

□ My check for $19.95 is enclosed. 

Please charge my □ Mastercard □ Visa 

Account Number_Exp_ 

Signature_ 


Address. 


A14 AND A15 AND M1=RAM CS 32-48K All Gates--74LS00 


Sinclair RAMs lack this 
decoding; you must add it to stack 
16K modules. 

Use of high-memory sites is 
limited by the 8K ROM. You can’t 
run Z80 machine language routines 
here, nor extend the display file 
past 32768 . Store variables and 
arrays in these high locations. 

To find the end of the display 

file, 

PRINT PEEK 16400+256*PEEK 16401. 
With the extended memory, you must 
POKE 16388,255 & POKE 16389,255 & 
NEW, after you power up, but before 
you load any program. (The ZX8l 
only checks memory addresses up to 
32768, and sets RAMTOP there when 
you power up.) If you poke RAMTOP 
too high, your computer will set it 
correctly after the NEW command. 



John L. Oliger 
Indianapolis, IN 


Ml 


32-48K 





PROBLEM-SOLVING CIRCUITS 


If your power line voltage is 
120V or higher and you use a 16K 
RAM, heat build-up in the ZX81 is a 
problem. Reducing the power supply 
voltage to the unit from about 10 
VDC to 8V with a pre-regulator will 
lower ZX81 regulator dissipation by 
40%. Voltage above 8V is mostly 
ripple and only heats up the ZX8l. 

My pre-regulator was built 
from junk parts, but commercially 
available units should work as 
well. The circuit in Fig. 1 is 
adapted from National Semiconductor 
Application notes. Use a suitable 
heat sink with the LM 340-8. 


If you're troubled by line 
interruptions, a simple circuit of 
4 or 5 silicon diodes in series 
with a 12V car or boat battery will 
take over on line failure and 
prevent program loss. Any silicon 
diode rated at 1A or above works 
OK. Since the forward voltage 
varies, try 4 or 5 in series to get 
8-8.5V into the ZX8l while 
operating. A small trickle charger 
will keep the battery charged, or 
use a normal charger occasionally. 

Or you could operate only 
from the battery and not use the 
plug-in ZX81 supply. The 9" 
portable TV I use as a monitor also 
operates directly from 12VDC. 

Ed Buttenhoff, Grand Rapids, MN 


Radio Shack #274-297 Radio Shack #274-286 

1/8” Pin Jack 1/8” Pin Plug 


From power 
supply 10 VDC 



8VDC to ZX81 


FIGURE 1 


On-off swi 





+ 


4 or 5 1N4001 silicon diodes 


8VDC output 
to ZX81 


Splice the output leads into the ZX81 power supply leads 
or use a 1/8” Y adapter. 

FIGURE 2 


6 







— - 


Can you improve excellence? 

We can. By adding our Memotech Memopak to the excellence of the ZX81 

we have achieved perfection. 


The growth of interest in computer use 
caused by the introduction of the Sinclair 
ZX81 has made new and exciting 
demands on the ingenuity of electronic 
engineers. At Memotech we have 
focused our attention on the design of 
inexpensive, reliable memory 
extensions. 

The Memopak is a 64K RAM pack 
which extends the memory of the ZX81 
by a further 56K. The new memory 
extensions are designed to be within the 
price range expected by Sinclair users. It 
plugs directly into the back of the ZX81 
and does not inhibit the use of the 
printer or other add-on boards. There is 
no need for an additional power supply 
or leads. 

Increase your memory. 

The Memopak together with the ZX81 
gives a full 64K, which is neither 
switched nor paged, and is directly 
addressable. The unit is user 
transparent and accepts such basic 
commands as 10 DIM A(9000). 

m€noT€cn 


Memotech Corp. 
7550 W. Yale Ave. 
Suite 220 
Denver Co. 80227 
Ph. (303) 986-0016 


0-8K . . . Sinclair ZX81 ROM 
8-16K . . . This section of memory 
switches in or out in 4K blocks to leave 
space for memory mapping, holds Its 
contents during cassette loads, allows 
communication between programs, and 
can be used to run assembly language 
routines. 

16-32K . . . This area can be used for 
basic programs and assembly language 
routines. 

32-64K . . . 32K of RAM memory for 
basic variables and large arrays. 

With the Memopak extension the 
ZX81 is transformed into 3 powerful 
computer, suitable for business, leisure 
and educational use, at a fraction of the 
cost of comparable systems. 


Free service on your Memopak. 

Within the first 90 days, should 
anything go wrong with your Memopak 
return it to us and we will fix or replace it 
free of charge. 

Try Memopak with no obligation. 

You can use our Memopak in your 
home without obligation. After 10 days, if 
you are not completely satisfied, simply 
return It for a full refund. 



r„ 


ixg- 


Mail to: Memotech Corp. 7550 W. Yale Ave. Suite 220 Denver, Colo. 

80227 

I understand that if I’m not completely satisfied, I can return my Memopak in 10 days for a 


1 


full refund. 


Price 

Oty. 

Amount 


Memopak 64k RAM 

$ 179.95 



□ Check 

Memopak I6k RAM 

$ 79.95 



□ Visa □ MC 

Shipping and Handling 

$ 4.95 J 


$ 4.95 

Exp. 



Total 



Act. No. . 


Signature _ 


Name_ 

Street 


City 


State 


Zip 


L 


T U.S. Dollars 



























BEGINNER'S BASIC—INKEY$ FUNCTION 

The INKEY$ function, though 
more obscure than commands like 
SAVE and RUN, is simple to use and 
adds a nice touch to your programs. 

INKEY$ plus a PAUSE command 
causes your ZX81 to wait, watching 
the keyboard until the user presses 
a key. That key is then accepted 
as input and the program proceeds. 

Substitute INKEY$ for an INPUT 
line. Say your program asks the 
user to choose between 3 options. 
Line 100 might read: 

100 PRINT "CHOOSE THE MONTH YOU 

WISH; 1. JAN 2. FEB 3. MAR" 

You could follow this with 

110 INPUT X 

120 IF X=1 THEN GOTO... 

130 IF X = 2 THEN GOTO... etc. 

The user must press his desired 
number, then ENTER or NEWLINE. 

When the input is a single 
digit, you can use the INKEY$ func¬ 
tion instead: 

no IF INKEY$ = "1" THEN GOTO... 


120 IF INKEY$r"2" THEN GOTO...etc. 
Note that you must include " " 
marks in the INKEY$ statement. 

With this kind of input, the 
user just presses his choice and 
the ZX81 carries on. Reducing the 
time and steps for input makes the 
program simpler for the user. 

You must also include a PAUSE 
statement BEFORE the INKEY$ lines. 
The PAUSE makes the computer wait. 
Add a line like; 

105 PAUSE 500 

The ZX81 waits about 10 seconds for 
input. Vary this time by changing 
the number after the PAUSE. 
Experiment to find a good time for 
your program. If you have an old 
8K ROM, add a POKE 16437,255 line 
after the PAUSE. (To check your 
ROM , see p.1 9.) 

Keep this in mind: INKEY$ 
doesn't wait, so the user cannot 
correct a mistake using the RUBOUT 
key. Use INKEY$ for input when you 
want a fast-moving program and your 
user has little chance of error. 


ZX81 OWNERS with 16K RAM! 
IT'S READY—ARE YOU? 



$14.95 + 
2.50 S&H 


If so. you get; 
*24-row/fun-screen displays 
*Near1y 2K of machine code 
for FAST real-time graphics 
*A 4K Star Atlas as the moving 
backdrop during enemy engagements 


16K Pro g rams for either ZX80-8K or ZX81 

*PLANE FRAME-model1ing for engineers 
*FUNDAMENTAL ANALYSIS-for stocks investors 
*P0LSAT & GEOSAT-space age Ham Radio uses 
*MATH PAK-Routines & Fit, Variance Analyzer, 
Statistics, and RPN Calculator 

*E,S.P.-test your precognition 
*Many others plus 6 IK 6-paks 
including Machine Code 
WRITE for free catalog. (In 
Europe, send U$1 bill or DM2 stamp: 
DELTAS0FT/0sterfeldstr.79D/D-2000 Hamburg 54 GER) 



*9-each fuel and skill levels that 
are interlocked for more "reality" ^ 
*4 ways to lose—no fuel, no oxygen, o 

no gun power, or no shields. 1 way ^ 

to win—destroy ALL enemy craft. ^ 

*An enemy data generator imbedded in 
the run as part of the "action" ^ - 

*"Blink"-less pauses in BASIC 
*Stick-on/peel-off custom keys 
*In-depth booklet explaining both o = 
the "game" and the program oj 

*Shipped on a certified cassette q-co 

1 copy each side 


fTlail coupon or copy with payment to: 

I ZETA Software/PO Box 3522/Greenvi1le,SC 29608 

I Enclosed is $_ DCheck □_ 

I for-copy(ies) of SCOUT FIGHTER ZX81 16K 

I plus $2.50 S&H for the order. 

I NAME 


ADDRESS 


CITY/STATE/ZIP_ 

Please allow 4 weeks if paid by check. 


8 







PUTTING FORTH ON ZX80/81S 


Although BASIC is the most 
common language for programming 
microcomputers, it is not the only 
one. Your ZX80 or 81 can learn 
FORTH, another high level language. 
(For an intro to FORTH, check out 
Byte Aug. 80.) FORTH has several 
advantages over other languages in 
certain applications, particularly 
in computers as controllers. 

Artie Computing announced that 
they were developing FORTH on an 
EPROM (erasable programmable read 
only memory) for the ZX8l, to be 
available in April. No word yet on 
their success. The package, 2 4K 
EPROMs on a board with users 
manual, sells for £60, or about 
$102 US. For info, contact Richard 
Turner, Artie Computing, 396 James 
Reckitt Ave, Hull, England HU8 OJA. 

Richard Holmes of Batavia, IL, 
has partially implemented FORTH on 
his ZX80 with 8K ROM and 16K RAM. 

He reports: 

My starting point was Threaded 
Interpretive Language by R.G. 
Loeliger ($18.95 from Byte Books, 

70 Main St., Peterborough, NH). 

This book contains most of the 
assembly code needed to implement 
FORTH on a Z80-based computer. It 
certainly makes the job easier, as 
long as you watch for the occasion¬ 
al typo. The worst problem with 
the book is that Loeliger's divi¬ 
sion routines are faulty. 

The book doesn't give routines 
to make FORTH work with the ZX80/81 
configuration. I had to write 3 
main machine-dependent routines— 
$ECH0 (writes a character to the 
screen), $KEY (displays the screen 
and gets keyboard input) and BASIC 
(returns control to the 8K ROM). 

Some requirements: on return 
from a USR call, registers lY and I 
must contain 4000h and lEh. Of 
course, SP must also be 
undisturbed. HL' must also be 
preserved. So on startup, FORTH 
must save SP and HL'. Then when 
the BASIC routine is called, it 


must restore SP and HL', load 4000h 
into lY (my FORTH code doesn't mess 
with I, so no need to reset it), 
and do a RET to get back to the 
ROM. My version also calls a 
routine that saves all the regis¬ 
ters in a block of RAM locations 
you can PEEK. This helps enormous¬ 
ly when debugging. 

$ECH0 and $KEY are based 
around calls to ROM routines. 

$ECH0 sets up a RST 10 call, which 
takes care of writing to the 
screen. You have to load 4000h 


into 

lY first. 

$KEY calls routines 

at 0229h (displa 

ys screen), 0F48 

(clea 

ns up keyboard handling) 

and 

07BD 

(decodes the keyboard). 


Again 

, 4000h mus 

t be loaded i 

nto 

lY; a 

Iso IX must 

be preserved 


be f 0 r 

■e these cal 

Is as the ROM 


doesn 

't preserve 

it. 



One other problem concerns 

chara 

cter sets. 

FORTH is bas 

ed 

around the ASCII 

(American Standard 

Code 

for Informa 

tion Intercha 

nge) 

set w 

hich includ 

es characters 

not 

in the ZX8l set. 

I defined an 

ASCII 

to ZX81 "m 

apping"; I re 

place 

neede 

d ASCII cha 

racters with 

invers 

ZX81 

characters 

as follows: 


ASCII 

ZX81 

ASCII 

ZX81 

a-z 

A-Z 

1 

• 

# 

= 

% 

£ 

& 

+ 

f 

ft 

@ 

9 

[,] 

(,) 

\ 

/ 



— 

> 

{,} 

<,> 


Rich added that he would, discuss 
putting FORTH on a ZX80/81 .'with 
anyone who's interested. Send him 
a SASE and $.50 to cover reproduc¬ 
tion of his materials. Richard S. 
Holmes, 1303 E. Wilson Apt. 4, 
Batavia, IL 60510. 


Howard Gladstone of Gladstone 
Electronic Distributors called to 
say they remastered all their 
tapes. Our review of their ZXAS 
and ZXDB programs reported trouble 
loading these tapes. This problem 
should no longer exist for tapes 
shipped after mid-April 1982. 


9 


DEAR EDITOR 


You can use your Sinclair 
computer to enjoy interactive 
communications (games, program and 
data transmitting/receiving) via 
the phone lines by building the 
very low-cost "Mickey Modem" as 
described in the Nov. 1978 issue of 
Kilobaud . Restrictions: both 
parties must have a Mickey Modem 
and use the same ROM; it only works 
on local phone lines (no long 
distance); and you must know your 
receiver's RAM capacity (you can't 
transmit 16K of program into IK of 
RAM space...but the receiver's 
modem could be hooked up to his 
recorder and the program saved.). 

Another goodie is the 
"Computer Music Box Peripheral" 
article in Popular Electronics , 

April 1978 . It shows how to build 
a low-cost, 12-tone, 4-octave music 
generator that can be tied to an 
output port such as shown in 
SYNTAX, Jan.81 p.7. 

Let's dig out those cheapie 
projects from old magazines we can 
easily adapt to OUR computers! 

Patrick Kelly, Los Angeles, CA 
We haven't tried these projects.—AZ 


Banta Software (RD #7, 
Bethlehem, PA 18015) has 3 very 
good programs on tape for $3.95— 
Football, Super Monzxer, and Murder 
in the RAM. All are 16K, run well 
and interesting to play. Banta 
will make the tapes good if they 
don't run. I had some trouble 
with a tape and they worked with me 
to get it running. I am happy with 
these programs—for $3*95 you can't 
go wrong. I will not recommend the 
monopoly game. 

Laverne Hoffman, Canby, OR 


With the 1 6K RAM, the new 
power pack is around 13.5-14V 
(depending on line voltage). The 
small electrolytic capacitor 


adjacent to the 5V regulator is 
rated at only 16V. After an hour 
or so of operation, a small "worm" 
crept up the TV display, typical of 
poor DC filtration. I changed to a 
470 mF at 25V for additional 
filtration and a margin of safety. 

My unit was reinstalled in a 
custom case with aluminum front and 
rear panels. I simply unbolted the 
5V regulator from the PC board and 
turned the heat sink around and 
rebolted it to the rear chassis 
panel. It runs cool as a cucumber. 
It was heating the the adjacent ICs 
after 15-20 minutes and causing the 
system to crash. Taking it off the 
PC board corrected this. 

Glen DeLong, Moneta, VA 


I would like to add a reverse 
video switch and a video monitor to 
my ZX 8 I as I did on my ZX 8 O. What 
modifications and connections do I 
need to make? 

Ronald Swager, Springfield, IL 

Unfortunately, you cannot simply 
switch a ZX8l to reverse video as 
you can a ZX80 (just a jumper on 
the board). We do not know how to 
reverse the video. 

To hook up a video monitor, 
pick up the video at pin 16 of IC1. 
Pick up a ground somewhere (like 
the modulator case). Connect these 
to the composite video input of any 
monitor with greater than,1000 Ohms 
input impedance. If the impedance 
is 50-75 Ohms, add a buffer. Use a 
source-follower or an emitter- 
follower. —KO 


I would like to praise the 
repair department at Sinclair for 
the fast, efficient and neat job 
they did for me and my bungling. 
Twice I damaged my ZX8l and/or RAM, 
returned them with payment for 
repair. They came back with remar¬ 
kable speed (2 weeks the first 
time) and no additional bill. I 
was amazed. Sinclair also replaced 


10 


a tape I could not get to load, at 
no charge. I thank them from the 
bottom of my RAM. 

Also, a supply house called 
Poly-Paks sells surplus computer 
goods. Their parts are reasonably 
priced and of good quality. They 
tell you exactly what you're order¬ 
ing, such as "ICs 100% guaranteed, 
untested." They are at 16-18 Del 
Carmine St., Wakefield, MA 01880. 

John Tiffin, Evanston, IL 

It's good to hear that not everyone 
has to wait interminably for ship¬ 
ments from Sinclair. If you're 
waiting for a repair from Micro¬ 
sync, see the story on p.14.—AZ 


of the connector must be partially 
removed for the ZX81. I added home 
brew memory using this technique 
for connecting to the ZX80/81. 

Hans Roensch 

Editor's note: Having been accused 
of running a catalog of things 
impossible to procure, I'm happy to 
report that The Fast One (data 
management program from England), 
reviewed in Apr.82, is available in 
the US from Mindware Inc. For a 
free catalog, contact Mindware, 70 
Boston Post Rd., Wayland, MA 01778, 
617/358-7175.—AZ 

COMPUTER CONTEST 


The Radio Shack 276-1558 40- Win $100 for your scheme 

pin card edge connector can be used involving a home computer. OCEAN 
with the ZX80/81. The connector is looking for practical, revenue- 

also requires the Radio Shack 40- producing ideas for any kind of 

wire flat cable. This leaves 4 home computer. Deadline is 30 June 

pins that must be hardwired to any 1982. For details, write OCEAN, PO 

peripheral devices. The two ends Box 3221, Springfield, VA 22152. 



d last, a comi 


>nsive text for your 
jpnplete BASIC Course is 
will immediately become 
an ihdisMnsible work of reference for all 
your ZXW programming 
Whether you have never done any 
programming or whether you are an 
experienced microcomputer user, the 
Complete BASIC Course will provide 
an invaluable aid 
HOW TO WRIT! PROGRAMS 
Even if the idea of writing programs is 
completely mystifying to you, the Complete 
BASIC Course will show you just how easy it 
is. In rvD time you will be able to write and 
enjoy complex programs for whatever you 
desire 


BASIC Course Programs 
on Cassotts 

All major programs in the BASIC Course are 
available pre-recorded in this set of 
cassettes. 




SUKtoJa' SX«l 
fetrtA. aQQm ivm& 
Ih'. Uimi 


Not Only so Programs for the 
Sinclair zxsi: 1K — 

Not only over 30 programs, from arcade 
games to the final challenging Draughts 
playing program, which all fit into the 
unexpanded IK Sinclair ZX81 Great value! 

Mochlno Language 
Programming Made Simple for 
the Sinclair — 

A complete beginner's guide to the 
computer's own language - Z80 machine 
language, Machir^e lar>guage programs 
enable you to save on memory and 
typically give you programs that run 10-30 
times faster than BASIC programs. 

ZXB1 ROM Disassembly Part A 
This book is for the programmer that needs 
complete answers about the ZX81. Dr. 

Logan has examined all routines in the ROM 
and here he comments on each one It 
covers all ROM locations from OOOOH to 
OF54H, and includes all functions except for 
the routines used in the floatir^ point 
calculator. 

ZX81 ROM Disassembly Part B 

In this companion volume to Part A Dr. 
Logan covers locations OF55H to IDFFH and 
includes all routines used in the ZX81 floating 
point calculator. These two books are a 
must for the experienced programmer 
understanding Your ZX81 ROM — 
A brilliant guide for more experienced 
programmers by Dr. Ian Logan, this book 
illustrates the Sinclair's own operating 
system and how you can use it. 


The Complete BASIC Course has over 
240 pages filled with information in an 
attractive durable ring binder - this is a lay- 
flat work of reference that deserves a 
place next to every Sinclair ZX81 
microcomputer. 

NUM8ROUS RXAMPL8S 

Every concept, every function is fully 
described by simple programs that you can 
enter on your Sinclair ZX81 in minutes 
The Complete BASIC Course contains 
over lOO programs and examples! These 
programs illustrate the use and possibilities 
of the Sinclair ZX81: 

• Home use 

• Financial analysis and planning 

• Educational applications 

• Games 

• Mathematical applications 

• Displays of Artificial Intelligence' 

■VRRV FUNCTION COVBR8D 

No matter what your application, what your 
confusion about any function, you will find it 
covered in the Complete BASIC Course. 


The Complete 

Sinclair ZX81 BASIC Course $35.0X3 0 
Basic Course 

Programs on Cassette S5.00 □ 

Not Only 30 Programs/Sinclair 
ZX81:1K $14.96 □ 

Machine Language 

Programming Made Simple $19.95 □ 
ZX81 ROM Disassembly Part A $14.95 Q 
ZX81 ROM Disassembly Part B $14.95 O 
Understanding Your ZX81 ROM $19.95 f") 


PQ Bax 480i Murray HSI Statioa 
NewM>X,N.YX)156 


NAME 


ADDRESS 


Shipping and handling 
Sales tax (NY residents only) 













■ Mathematical and scientific functions 
accurate to 8 decimal places 

■ Unique one-touch entry of key words 
like PRINT. RUN and LIST 

■ Automatic syntax error detection and 


If you already own a ZX80 

The 8K Extended BASIC 
chip used in the ZX81 is available 
as a plug-in replacement for your 
ZX80 for only $39.95, plus shipping 
and handling—complete with new key¬ 
board overlay and the ZX81 manual. 

So in just a few minutes, with no 
special skills or tools required, you can 
upgrade your ZX80 to have all the 
powerful features of the ZX81. (You’ll 
have everything except continuous dis¬ 
play, but you can still use the PAUSE 
and SCROLL commands to get moving 
graphics.) 

With the 8K BASIC chip, your 
ZX80 will also be equipped to use the 


Introducing 
the Sinclair ZX81 


If you’re ever going to buy 
a personal computer, now is the 
time to do it. 

The new Sinclair ZX81 is the 
most powerful, yet easy-to-use 
computer ever offered for anywhere 
near-the price: only $149.95* completely 
assembled. 

Don’t let the price fool you. The 
ZX81 has just about everything you 
could ask for in a personal computer. 

A breakthrough 
in personal computers 

The ZX81 is a major advance over 
the original Sinclair ZX80—the world’s 


largest selling personal computer and 


easy editing 


ZX Printer and Sinclair software. 


the first for under $200. 

In fact, the ZX81’s new 8K Extended 
BASIC offers features found only on com¬ 
puters costing two or three times as much. 
Just look at what you get: 

■ Continuous display, including moving 
graphics 

■ Multi-dimensional string and numerical 


■ Randomize function useful for both 
games and serious applications 

■ Built-in interface forZX Printer 

■ IK of memory expandable to 16K 

The ZX81 is also very convenient 
to use. It hooks up to any television set 
to produce a clear 32-column by 24-line 
display. And you can use a regular 


Order at no risk** 

We’ll give you 10 days to try out 
the ZX81. If you’re not completely satis 
tied, just return it to Sinclair Research 
and we’ll give you a full refund. 

And If you have a problem with 
your ZX81, send it to Sinclair Research 


arrays 


cassette recorder to store and recall 


within 90 days and we’li repair or replace 


* Plus shipping and handling Price includes connectors proqrams bv name ^10 Charge 

for TV and cassette. AC adaptor, and FREE manual, ^ ’ -Does not apply to ZX81 kits. * 



NEW SOFTWARE:Sinclair has 
published pre-recorded pro¬ 
grams on cassettes for your 
ZX81, or ZX80 with 8K BASIC. 
We’re constantly coming out 
with new programs, so we’ll 
send you our latest software 
catalog with your computer. 


ZX PRINTER: The Sinclair ZX 
Printer will work with your ZX81, 
or ZX80 with 8K BASIC. It will 
be available in the near future 
and will cost less than $100. 


16K MEMORY MODULE: 

Like any powerful, full fledged 
computer, the ZX81 is expand¬ 
able. Sinclair’s 16K memory 
module plugs right onto the 
back of your ZX81 (or ZX80, 
with or without 8K BASIC). 
Cost is $99.95, plus shipping 


ZX81 MANUAL: The ZX81 
comes with a comprehensive 
164-page programming guide 
and operating manual de¬ 
signed for both beginners and 
experienced corriputer users. 
A $10.95 value, it’s yours free 
with the ZX81. 


and handling. 









Introducing 
the ZX81 kit 


If you really want to 
save money, and you enjoy 
building electronic kits, you 
can order the ZX81 in kit form 
for the incredible price of just 
$99.95* It’s the same, full-featured 
computer, only you put it together 
yourself. We’ll send complete, easy- 
to-follow instructions on how you can ^ 
assemble your ZX81 in just a few hours.^ 
All you have to supply is the soldering iron 

How to order 

Sinclair Research is the world’s larg¬ 
est manufacturer of personal computers. 

The ZX81 represents the latest 
technology in microelectronics, and it 
picks up right where the ZX80 left off. 
Thousands are selling every week. 

We urge you to place your order 
for the new ZX81 today. The sooner you 
order, the sooner you can start enjoying 
your own computer. 

To order, simply call our toll free 
number, and use your MasterCard or VISA. 

To order by mall, please use the 
6pupon. And send your check or money 
order. We regret that we cannot accept 
purchase orders or C.O.Dis. 

CALL 800-543-3000. Ask for op¬ 
erator #509. In Ohio call 800-582-1364. 

In Canada call 513-729-4300. Ask for 
operator #509. Phones open 24 hours 
a day, 7 days a week. Have your Master- 
Card or VISA ready. 

These numbers are for orders 
only. For information, you must write to 
Sinclair Research Ltd., 2 Sinclair Plaza, 
Nashua, NH 03061. 


PRICEt QTY. AMOUNT 


105SX 


TOTAL 


MAIL TO: Sinclair Research Ltd., One Sinclair Plaza, Nashua, NH 03061 


NAME 


ADDRESS 


CITY/STATE/ZIP 

t U S. Dollars 



$149.95 



__^ ^ 

2X81 Kit 

99.95 



Hr 8K BASIC chip (for ZX80) 

39.95 



Fi 6K Memory Module (for ZX81 or ZX80) 

99.95 



Shipping and Handling 

4.95 


$4.95 











2K CONVERSION WITH 6116S 


MICROSYNC SPEAKS 


While assembling my ZX81, I 
noticed the provision for adding a 
2Kx8 RAM. While soldering sockets 
to the PC board, I included both 
the 18-pin sockets for the 2114s 
supplied with the kit, and a 28-pin 
socket for the alternative memory. 
(The middle plastic portion of the 
28-pin socket must be cut out so it 
fits over and around one of the 18- 
pin sockets.) 

I ordered a 6116 2K memory by 
mail. When it arrived, I simply 
replaced the two 2114s with the 
6116. The conversion was simple 
and works fine. I can now fill the 
screen with graphics! 

My only problem was assuming 
that the position of jumper J1 on 
the PC board corresponded with that 
shown on the schematic. It didn't. 
When you install the jumper, make 
sure to use the component I.D.s 
printed on the PCB front. 

Insert the 24-pin DIP with the 
proper orientation and in the lower 
24 pins of the 28-pin socket 
(similar to the 8K ROM). 

I used the Hitachi HM6116P-3 
2Kx8 static CMOS RAM from Jameco 
Electronics (1355 Shoreway Rd., 
Belmont, CA 94002, 914/592-8097, 
hrs Mon-Sat 8-5 PST). Actually, 
their catalog lists the device as 
P-4, but I received a P-3 and it 
works great. Cost: $14.95 plus $1 
postage, $1.50 insurance ($2 each 
postage and insurance for foreign 
orders), plus 6% tax (CA only). A 
data sheet is $.25 extra. 

I'll use the 2114s for another 
project, but have toyed with the 
idea of a 3K conversion. This 
would involve stacking the 6116 on 
two sockets to put it above one of 
the 2114s. Then some PCB tra ces 
would have to be cut and two RAM CS 
signals created. My prototype 
requires only an additional 74LS00 
to gen erate them from the existing 
RAM CS and A11. 

Paul J. Brogger, Tumwater, WA 


Yes, Virginia, there is a 
Microsync. SYNTAX arranged an ex¬ 
clusive, secret interview with Bob 
Allen, Service Manager. 

Microsync exists to sevice 
Sinclair computer equipment. Now, 
about 12 people repair up to 100 
machines daily. Most are kits, 
although less than 1/5 of kit- 
builders need service assistance. 

Many readers ask if ULA (IC1) 
chips fail more often than others. 
Bob Allen tells us all chips get 
replaced with equal frequency in 
both kit and factory-built units. 
ULAs do fail more often if instal¬ 
led backward. Although LOAD/SAVE 
problems can result from ULA 
failure. Bob says they usually have 
some other cause. 

From experience to date. Bob 
feels the maintainance pricing ac¬ 
curately reflects the reliabilty of 
Sinclair computers. 

Microsync's goal is to 
receive, repair, test and ship most 
machines in 4 working days. Dur¬ 
ing this startup phase. Bob says 
delays do reach 3-4 weeks. Just 
before press time. Bob told us they 
were servicing items that arrived 5 
days earlier. 

When your machine arrives. 
Microsync date-stamps it immediate¬ 
ly. Unless the computer was pre¬ 
viously serviced unsatisfactorily 
by Microsync, your computer moves 
to service in this date order. 

At the service area. Microsync 
dates the order and begins repairs. 
When done, each repair goes through 
a QC test by the lead technician. 

Next the machine moves to an 
outgoing area where operators key 
administrative data into the compu¬ 
ter system. Within 24 hours, the 
shipping papers are printed and the 
machine entered for UPS shipping. 

This is basically a first-in, 
first-out system and locating your 
unit prior to completion requires 
looking through the boxes. Bob 
offers this advice when you must 


14 


check the status of a repair: Use 
EXACTLY the same name, include your 
ZIP code, tell EXACTLY when you 
sent your unit, whether you used 
parcel post or UPS, and if your 
unit is a kit or factory-built. 

Bob also points out that 
Microsync will need 3 days to get 
your reply in the mail to you. 

SYNTAX offers additional tips: 

• Photocopy the front of the box 
before you send it. If you in¬ 
quire, send the photocopy with your 
letter. 

• Make a packing slip for the 
package you send, and keep a copy 
to send if you must inquire. 

• Send your computer by UPS and 
insure it. Use UPS Blue Label for 
faster shipping (2 days). 

Bob says common shipping prob¬ 
lems result from using flimsy boxes 
or failing to write your name on 
the box as well as the wrapping 
paper. He suggests you use the 
Sinclair box if possible. Further, 
shipping to Sinclair in Nashua 
gives you no advantage. 

Only computers with damaged 
boards are returned by Microsync as 
unrepairable, according to Bob. 

About li of machines come back 
to Microsync as not properly re¬ 
paired. Bob suggests you return 
the machine in their box, making it 
clear that this unit has been in 
before. Many returns are "no prob¬ 
lem found" cases where the customer 
omitted the power supply and the 
power supply is the problem. 

Power supply problems can 
cause a number of symptoms, includ¬ 
ing LOAD/SAVE problems with the 16k 
RAM attached, left-to-right bars 
that slowly rotate on the screen, 
and others. If you have access to 
a regulated power supply with plen¬ 
ty of current capability and low 
ripple, substitute it and see if it 
cures your problem. If you test 
the power supply yourself, check 
for increased ripple as well as for 
proper voltage. 

Bob Allen says: "If it's under 
warranty and works except with the 


SYNCH RO-SETTE 

FORTHEZX-80&ZX-81 
8KROM IK - 16K 

GAMES-EDUCATIONAL-BUSINESS 
GRAPH ICS-TUTORIAL-ETC. 


24 HR HOTLINE - 800-543-1300 
IN OHIO-800-582-1364 

Ask for operator No. 383 


12 monthly issues - 6 bi-monthly 
cassettes containing at least 6 programs each 

$39.50 


ILL. Residents add $2.07 tax 
outside USA add $10.00 

s&sco. 

388 West Lake Street • Addison^ IL, 60101 

(312) 628-8955 


RAM, send ALL the pieces." 

If you installed an R-PAK 
wrong in your kit, SAVE THE BOARD 
AND SACRIFICE THE R-PAK. Don't 
attempt to remove multiple-lead 
components without de-soldering 
tools. Solder-wick won't suffice. 

SYNTAX asked Bob what causes 
delays in service. He replied: 

"The worst thing is money separate 
from the unit." He explained that 
this puts the unit in a hqlding 
area, generates a letter to the 
sender, and may require a'search of 
other correspondence to locate the 
payment. All of this is labor- 
intensive and time-consuming. 

LOAD/SAVE problems and RAM 
problems take more diagnostic time. 
Also, machines with no problem 
found get extra testing to avoid 
returning defective machines and 
annoying customers. Machines re¬ 
quiring estimates also suffer 
delays for correspondence. Kits 
with "white screen syndrome" also 
take longer to diagnose. 


15 




KOPAK GIVES 

YOU THE 

POWER! 

KOPAK’STM Touch-A-Matic gives you 

KOPAKTM is now offering The Source* 

the power to type more accurately and 

‘America’s Information Utility’. The 

much taster. No wires, no soldering, 

Source* gives you the power to access 

simple to install. Our unique vinyl over- 

a wide array of services including: 

lay guides your fingers to the correct 

• Barter • Shopping • Business Infor- 

keys. Touch typing now possible with 

mation • Career Network • Electronic 

your Sinclair* or MicroAce*! 

Mail • Medical Advice • UPl News 

$9.95 

Service and much more. A modem is 


required to use The Source*. 

The KOPAKTM Sinclair* female Con- 

Source ID $100. 

nector gives you the power to use the 


Z-80 bus. Edgecard connectors specif- 

More POWER on the way! KOPAK’STM 

ically made for Sinclair* computers. 

Coming Creations: 

• 46 Pins, 23/23 • All pins are gold 

The KOPAKTM rs- 232 Interface 

plated • polarizing pin for correct 

The KOPAKTM Bus 

alignment everytime! Available with 

The KOPAMATICTM Keyboard 

Solder-Tail, Wire-Rap and PCBoard. 

The KOPAKTM Printer 

$14.95 

KOPAKTM Memory Products 


The KOPAKTM Disc 

KOPAK has the POWER to deliver! ’ 



© 1982 KOPAK Creations Inc. 

KOPAK Creations Inc. 

TM Trademark of KOPAK Creations Inc. 

Dept. SX 

Sinclair* is a trademark of Sinclair* 

448 West 55th Street 

Research LTD. 

New York, NY 10019 

MicroAce* is a trademark of MicroAce* 

(212) 757-8698 




BEGINNERS’ ML—REGISTER TO REGISTER 
(Number 5 in a series) 


There are more than 100 1-byte 
instructions for data manipulation 
between single registers. These 
are grouped as "LD r,r"; "ADD r,r"; 
"SUB r" (from A); logical opera¬ 
tions (AND r, OR r, and XOR r); and 
"CP r" (comparisons to A). Here 
we’ll look at loading, adding and 
subtracting. 

LD r,r is the general instruc¬ 
tion for data transfers between 
single registers. That means that 
values must be less than 256, 
because no single register can hold 
more than 8 bits, or a value of 
255. Register pairs are just 
that—two 8-bit registers. 

Before you can transfer data 
with an instruction such as LD C,E 
(load data in E into C), the E 
register must have data in it. In 
practice, all registers have data 
in them at all times, but rarely 
the data you want. So you must 


load the "source" register (E in 
our example) with data before 


moving 

it to the 

"destina 

tion" 

registe 

r (C in our example). 

Adding and subtracti 

ng single 

registe 

rs are sim 

lilar in 

that all 

operations are be 

itween the A regis- 

ter (Ac 

cumulator) 

and the 

other 

single 

registers 

(B,C,D,E 

,H, or L) 

or the 

HL registe 

!r pair. 

(ADCs and 

SBCs are identical to ADD 

s and SUBs 

except 

that they 

include 

the Carry 

bit in 

the Flags 

register 

'.) 

Fo 

r example, 

. let’s 1 

oad B with 

132, C 

with 45, a 

ind D with 36. 

Then we 

:’ll add B 

and C and subtract 

D twice 

i • 

* • 



REM ADD 

. DECIMAL= 

MNEMONIC 

COMMENT 

xxl 

6 

LD B,n 


xx2 

132 

(data) 


xx3 

14 

LD C,n 


xx4 

45 

(data) 


xx5 

22 

LD D,n 


xx6 

36 

(data) 


xx7 

120 

LD A,B 

; B to A 




(A=132) 

xx8 

129 

ADD A,C 

;C+A=177 




(A=177) 

xx9 

146 

SUB D 

;A-D=141 




(A=141 ) 

xIO 

146 

SUB D 

;A-D=105 




(A=105) 


REM ADD lists relative addresses. 
You can find the decimal codes for 
instructions in your 8K ROM or ZX8l 
manual. Appendix A (the character 
set). The first and third columns 
list decimal code and corresponding 
Z80 mnemonic. These codes also 
serve as character codes, in BASIC. 
You can find explanations for in¬ 
structions in assembly language 
manuals such as Zilog’s Z-80 Assem¬ 
bly Language Programming Manual. 

After "running," A will con¬ 
tain 105 while B,C and D will all 
contain their "loaded" values. 
Except for the A and Flags regis¬ 
ters, all registers keep their data 
intact until specifically altered. 

Next month: Exchanging Registers 

Jon Bobst, Zeta Software, P.O. Box 
3522, Greenville, SC 29608-3522 


16 





ZX81 INTRO 


BYTESAVERS HINT—8K 


Here is a little subroutine I 
use at the beginning of user- 
friendly programs. Just RUN to 
start or call it from within your 
program by GOTO 60 or GOSUB 60. If 
you use GOSUB 60, change line 270 
to RETURN and delete 999. To stop 
execution in midstream, press 
BREAK. 

This routine uses just about 
exactly IK RAM. 


A. Kohlenberg, Fremont, OH 


60 PRINT RT I RM Z 

65 PRUSE 10© 

70 PRINT 

80 PRINT "I RM R HOME PERSONRL. 
COMPUTER" 

85 PRUSE 150 
9© PRINT 

100 PRINT "I CRN DO MRNY THINGS 
AND" ^ "THE BEST IS***^“ 

105 PRUSE 15© 

110 CLS 
120 PRINT 

130 PRINT "I NEUE MAKE MISTAKE 
S" 

135 PRUSE 100 

140 PRINT AT 2,7;"WHOOPS" 

145 PRUSE 100 

150 FOR Y=25 TO 7 STEP -1 

160 PRINT RT 2,Y;"S" 

170 PRINT RT 2,Y;" " 

180 NEXT Y 

190 PRINT RT 1,6; "jS" 

200 FOR R=18 TO 1 STEP -1 
210 PRINT RT R,6;"R“ 

220 PRINT RT R,6;" " 

230 NEXT R 

240 PRINT RT 1,6;"R" 

250 PRINT RT 10,8; "WEL.L., RI_MOSX 
NEWER" 

260 PRUSE 150 

270 PRINT RT 11,15;"BYE" 

999 STOP 

SYNTACTIC SUM: 33973, 8K 


ATTENTION SUBSCRIBERS: Some makers 
and distributors of ZX-related 
products have asked about mailing 
to our subscription list. We think 
you would find some of these mail¬ 
ings useful or informative. How¬ 
ever, your name and address are 
private (the reason we don't print 
complete addresses unless asked to 
by the person). If you would not 
like to receive such information in 
the mail, please let us know. If 
we don't hear from you, we'll pre¬ 
sume you would like to receive ZX- 
related literature by mail.—AZ 


If you are using a PRINT after 
a line number simply to add an 
empty line, use two commas instead. 
Often empty lines are useful to 
clean up a screen display. These 
two programs display the same 
spacing—the second saves you four 
bytes: 

Program 1 
10 INPUT A 
20 PRINT A 
25 PRINT 
30 INPUT B 

40 PRINT B (bytes used=34) 

Program 2 
10 INPUT A 
20 PRINT A 
30 INPUT B 

40 PRINT ,,B (bytes used=30) 

Each substitution of commas for 
blank PRINT lines saves four bytes. 

Dave Hallas, Kansas City, MO 


NOW AVAILABLE 


keyboQfd. 

^ ^conversions 

• Standard Computer Keyboard 


• Type programs in half the time 

• Minimize errors 

• Wired keyboard hooks up in minutes 

Plans for keyboard conversion with reverse video 

NOW $5.00 

Keyboard with complete parts and plans NOW $55.00 
Wired keyboard, complete with plans MW $75.00 

Add $5.00 mailing charge for continental U.S. 

Other locations write for details. 


Mail for information: 

LJ.H. Enterprises 

P.O. Box 6305, Orange, CA 92667 
or can 714/547-8717 


17 




IC INVENTORY —4K/2K 


Some hobbyists have trouble 
keeping track of parts. This 
program, written for the CD4000 
series of ICs and using the 4K ZX80 
ROM and at least 2K RAM, can be 
adapted for any series of things 
following consecutive numbers. It 
is beneficial to keep two lists for 
each series—one of those in stock 
and one of those used in circuits 
for emergency substitutions. 

The first part of this program 
is also useful for setting aside 
memory for machine code routines. 

Enter line 1: 

1 REM 480 BYTES FOR DATA 0123 
456789012345678901234567890 
Then type EDIT, RUBOUT, 2, NEWLINE. 
This duplicates line 1 as line 2 as 
saves lengthy typing. Repeat 
procedure for line 3. 

Next POKE out the newline 
characters at the ends of lines 
1&2, combining all three into one 
long REM statement for the data: 
POKE 16477,61 
POKE 16531 ,61 

Then repeat the duplicating 
procedure: 

EDIT, RUBOUT, 2, NEWLINE 

EDIT, RUBOUT, 3, NEWLINE 

Set the memory behind the first REM 

to zeros: 

10 LET A=16426 
20 FOR B=0 TO 480 
25 POKE A+B,0 
30 NEXT B 
RUN 

This leaves 1 REM on the screen 
and about 2/3 blank, with 90 above 
the E in line 10. Line 1 now has 
482 data spaces available if 
nothing larger than 255 is entered. 
Do not enter quantities greater 
than 255. Each quantity is held in 
1 byte, with a 255 maximum. 

Now enter the following 
program. Note that line 25 is 
changed. After pressing RUN, the 
screen takes at least 5 seconds to 
display. 

Gyro Burns, Athens, OH 


10 LET A=16426 
15 PRINT,"CURRENT LIST" 

20 FOR B=0 TO 480 
25 IF PEEK(A+B)>0 THEN GO SUB 
300 

27 IF PEEK(A+B)>0 THEN PRINT, 

30 NEXT B 
40 PRINT 

50 PRINT "FOR CMOS IC S" 

60 PRINT "INPUT THE NUMBERS A 
FTER CD4 —" 

70 INPUT B 

80 IF B>480 THEN PRINT "OVERR 
ANGE" 

85 PRINT 

90 IF B>480 THEN GO TO 60 
100 CLS 

110 GO SUB 300 

130 PRINT " IN STOCK" 

140 PRINT "LIST OR CHANGE? L/C" 

150 INPUT C$ 

155 CLS 

160 IF C$="" THEN GO TO 45 
165 IF C$="L" THEN GO TO 10 
170 PRINT "TO WHAT?" 

180 INPUT D 
190 POKE (A+B),D 
195 GO SUB 300 
197 PRINT 
200 GO TO 45 
300 PRINT "CD4"; 

305 IF B<100 THEN PRINT "0"; 

310 IF B<10 THEN PRINT "0"; 

320 PRINT B, 

330 PRINT PEEK(A+B); 

350 RETURN 

390 REM CMOS IC LIST 5/1/82 
Syntactic Sum: -30692, 4K 

To check that your 16K RAM pack is 
working OK on your ZX8l, follow 
these steps: 

Pull the power jack and plug it 
back in to clear the machine. 

Type in the immediate mode (with no 
line number): 

PRINT PEEK 16388+256*PEEK 16389 
Press ENTER or NEWLINE. 

If your 16K RAM is OK, the answer 
on the screen is 32768. Try it 
without the RAM attached. With 
just the internal IK RAM, the 
answer is 17408. This routine 
checks to see where the top of RAM 
is and reports the highest address. 


18 




SOFTWARE REVIEW—8K/1K SLOT MACHINE 


Here's another free sample 
software review—a program directly 
from New England Software's tape. 
Try it out and see for yourself. 

Part of a package available 
for $10 on tape from the address 
below, Slot Machine runs in IK, no 
small feat for a game with its 
features. The display could be 
more elaborate, but only at tremen¬ 
dous memory expense. If you have 
just IK on your 8K machine, you'll 
be surprised at what it can do.—AZ 


This program simulates a 
dollar slot machine. RUN the pro¬ 
gram to start; to exit enter a 
double letter such as ZZ instead of 
a bet. Enter your bet each time. 
The computer displays each window 
in succession in SLOW. Six differ¬ 
ent symbols are used. Payoffs are: 

W—2 to 1 
5 to 1 

3 of a kind—20 to 1 
Rather than giving you money 
(who gives away money these days?) 
the computer starts you at $0 and 
tracks wins and losses. The pro¬ 
gram is set to pay back 95% of all 
money entered, so sometimes you win 
and sometimes you lose. 

In lines 35, 45 and 50, use 
keywords TO or AT. In subroutine 
400 a FOR-NEXT loop is used instead 
of PAUSE to prevent screen flicker. 
To save valuable memory in IK, 
nearly all numbers are expressed in 
terms of D, E and F (already de¬ 
fined variables). 

Here's a neat trick to save 
memory. If you use a number sev¬ 
eral times in your program, replace 
it with a defined variable. For 
example, if you use 1 several 
times, enter a line LET A=1. Use A 
in place of 1 throughout your pro¬ 
gram, A-A in place of 0, A+A in 
place of 2. You may be surprised 
at how much memory you save. 

Bob Ferguson, New England Software 
Box 691 , Hyannis, MA 02601 


5 LET E=2 
10 LET F=3 
15 LET ^f=E-E 
£0 RRND 

25 LET D=RND^^E 

30 IF D>=F-E THEN PRINT "TRY Y 
OUR LUCK" 

35 IF D<F-E THEN PRINT “PRY HE 
TO UIN" 


4-0 LET D=2© 

4.5 PRINT “NOU RT : M 
5© PRINT “PLRY $1 TO $5" 

6© INPUT B 

7© IF B<F-E OR B>E+F THEN GOTO 
Ds-F 

80 PRINT RT E-E^E-E;"i 


90 

10 © 

11 © 

120 

130 

14-0 

15© 

IS© 

170 

IS© 

190 

20 © 

210 

22 © 

230 

24.0 

25© 


270 

280 

290 

300 

31© 

320 

4 . 0 © 

4-10 

Vi-,— 

4-30 

4-4-0 



E*F; 


D.-'E, 


, E-E; 


IF X < >Y OR X < > 


PRINT 
PRINT 
PRINT 
PRINT 
PRINT 
PRINT 
GOSUB 
LET X=R 
PRINT TRB 
GOSUB 
LET Y=R 
PRINT TRB 
GOSUB E>^D 
LET Z=R 
PRINT RT F 
LET H=H-B 
IF XOF THEN 
1 THEN GOTO O 
250 PRINT "YOU 
LET C=E 

IF Y=F THEN LET C=E+F 
IF X=Y RND X=Z THEN LET 
LET M=H-S-C*B 
PRINT C*B 
GOTO D+D 

P = 1NT {RNOJt {E«-F> > 

FOR Z=:E-E TO 65 
NE.XT Z 

PRINT CHR* (128-fR*E) ; 

_ RETURN 

SYNTRCTIC SUM:33186, 8K 

(Line 80-all graphics space,7,7,7, 
space,etc. Line 90-graphics space, 
3 normal spaces, etc. Line 100-all 
graphics space,6,6,6,space ,etc.) 


UIN 


C=D 


DEFECTIVE 8K ROMS: Brad Lange of 
Enid, OK, reports that he and 
friends bought 6 ZX8l kitsyDec.8l- 
Apr.82. All 6 kits contained the 
old 8K ROM with bugs. (Old 8K ROMs 
give some arithmetic errors and 
crash after PAUSE commands.) 
Sinclair said they were unaware of 
this problem and replaced their 
ROMs free. Bruce Livett of 
Montreal, Quebec, finally got his 
replacement 8K ROM in Feb.82 (or¬ 
dered Jun.8l) and also found it was 
defective. To check that your 8K 
ROM is the new, corrected version, 
type in PRINT PEEK 54. Old ROM 
gives 132. Improved ROM gives 136. 
Test from Ian Logan, SYNTAX Dec.81 


19 






Paul Pittari reports that he 
followed the Sinclair schematic for 
the power converter in the 16K RAM 
pack with 3 substitutions. 

He used a TIP34A transistor to 
replace the ZTX750, a 1N4007 to 
replace the BA 221, and an old AM 
radio antenna to make the auto¬ 
transformer. He called later to 
say the transformer loaded down, 

12V dropped to 10V, so he had to 
rewind it with heavier wire. 

CLASSIFIED ADS 


You can reach thousands of ZX80/81 
users for just $9 a line. Send us 
your ad copy, typed 35 char, per 
line, with a check (NO CREDIT CARDS 
OR PHONE ORDERS, please) by the 
15th of any month. Your ad will 
appear in the next month's issue. 

To repeat an ad, send another ad 
order with check by the 15th. We 
have not seen all products offered 
and take no responsibility for 
advertisers. SYNTAX, RD 2 Box 457, 
Harvard, MA. 

7 IK ZX81 GAMES ON CASSETTE--$10.00 
Mastermind, Slot Machine, Craps, 

Sub Rescue, White Hot Number, and 
more. NEW ENGLAND SOFTWARE,Box 691, 
Hyannis, MA 02601. (Also for ZX80) 

AT LAST!Programs for the collector; 
Antique,Art,Baseball card,Beer can. 
Book,Coin,Comic book,Football card. 
Record album and Stamp.Mass Storage 
Inventory.GUARANTEED easy loading. 
Menu format.bistable.Search,Check 
inventory,Total cost/value and more 
ZX80/81/M.A.8KROM/16KRAM.Cassette & 
Manual.^4.95+1.05P.ea. M.C.Hoffman 
P.O. Box 117, Oakland, N.J. 07436 

NEW: For the ZX81 w/16K RAM Pac. 
Geometry and graphic trig data, 
resonance and matching calculations 
+0hms Law; 6 programs (17K) in all! 
Straight forward BASIC, use and 
learn at the same time! 

Send $14.95 to: SOFT-WAY 
3308 Midway Dr. Dept. 124 
San Diego, CA. 92110 


REMOVING ICS SAFELY AND CHEAPLY 

Instead of buying costly 
tools for IC removal, get binder 
clips (with springs). For less 
than $.40, the large size will 
handle 40-pin ICs; the small size 
(less than $.20) works for smaller 
ICs. The metal clip ties the pins 
together, so no static problems 
from plastic tools. The spring 
tension bends pins inward slightly, 
making them easier to put in sockets. 

To remove an IC, put the clip 
down to the top of the socket. 

Gently pry up alternate ends of the 
IC with a small blade or screw¬ 
driver to loosen it gradually. As 
the pins emerge, slide the clip 
down the legs for a better grip. 

Lift the IC out and place it on 
aluminum foil or conductive foam. 

To insert an IC, hold it in 
the clip and set the pins in the 
socket. Press down gently in the 
center of a small IC or on alter¬ 
nate ends of a large IC until it is 
entirely seated. Be careful not to 
bend the pins; they can snap off. 

Herb Sturges, Orinda, CA 


EZRA GROUP II 
EZRA GROUP II 

The ZX80/81's are making a name 
with LOW prices... 

WE CHALLENGE THE SOFTWARE COMPANIES 


TO LOWER THEIR PRICES! 

for ZX81/ZX80/8k ROM 
IK and 16K RAM versions 
Moving Billboard.!!SIDEWAYS!!..1.00 

Horse Race.1.00 

Quilt Painter.(from Keyboard)..1.00 

Metric Conversion.1.00 

Functorial Hypercube Course 

with Programs.1.95 

Postage per order.50 


Self Addressed Stamped Envelope 

Gets You Our Goodies Catalog 
ALL ORDERS AND CATALOG REQUESTS GET 
FREE PROGRAM. 

EZRA GROUP II 
EZRA GROUP II 

P.O. Box 5222 San Diego, California 
92105 


20 






ZX81 PROGRAMS--All 6 fit IK RAM 
HANGMAN word game, NIM number game 
DICEPLOT simulator, CRAPS gambling 
PRIME generator + FACTOR extractor 
All quality programs. 

NO TAPES! Save these yourself and 
save money. Listings+instructions 
ONLY $4. R. Howard 3752 Rolison #21 
Redwood City, Ca 94063 

BRITAIN'S BEST TEACHING SOFTWARE! 
Programs for 4-12 graders at home 
or at school - math, English, 

French, science, history, etc. 
Excellent reviews. Most cost £4.00 
Send reply coupon for list to: 

AVC SOFTWARE PO BOX 415 BIRMINGHAM 
B17 9TT, UK 

ZX81 16K SOFTWARE--Send SASE for 
discriptions. All cassette 
BRITTANYSOFT LTD., P.O. Box 1043 
Twin Falls, ID 83301 208-324-3086 

NEW...ZX-CALC The new Electronic 
Spread Sheet program for the ZX80,1 
(w/8K,16K). This large sheet 30co. 

X 45li. can be adapted to may of 
your needs: Budget, Inventory, For- 
casting, Etc. This program on cass¬ 
ette is only:$16.00+1.50 postage + 
handling. MAIL CK. or M.O. to: 
SOFTWARE APPLICATIONS,PO BOX 1922 
ATASCADERO, CAL. 93422 

Female Connectors for Sinclair 
Users. 23 dual pin keyed, WW or 
eyelet avail., please specify. $10 
ppd. each, M.O. or check only. RG 
Enterprises, PO Box 271173, 
Escondido, Ca. 92027. Ca. res. add 
67o sales tax. 

PUT THAT ZX80/81 TO WORK with SORT. 
This great collating tool can count 
1000's of items in up to 29 catego¬ 
ries on just IK!! $3 gets you list/ 
explanation to learn/build on. 

MAD DOG TANK BLASTER-ZX81-16K shows 
you how to create that masterpiece 
of your dreams. Moving tank-soldier 
Bullets/explosions all explained. A 
terrific game/a real idea generator 
List w/complete instructions $6.95 
TOM WOODS Box 64 Jefferson,NH 03583 


A PLAYER ZX81 cassette,$6.95pp,with 
your 8K-1K/16K system and recorder 
become a 124 note MUSIC SYNTHESIZER 
W Maples 688 Moore St LKWD,C0 80215 

+>v*dISCOUNT ZX- 81 (IK) PROGRAMS*** 

8 Programs on each.$8.00 a tape 
TAPE(1)GAMES:Lunar Lander etc. 

TAPE(2)DIET:Calorie Computings etc. 
TAPE(3)HOME:House Security etc. 

TAPE (4) BUSINESS: Salary, Markup7o etc. 
TAPE(5)MATH:Drills for all ages. 
TAPE(6)GEOMETRY:Pythag. Ther. etc. 
TAPE(7)DESIGN:Computer Clocks etc. 
TAPE(8) INVESTMENT: Interest 7o etc. 
TAPE(9)QUIZ:Various for all ages. 
TAPE(10)GENERAL:1 of each category. 
ROMAN SOFTWARE 788 Mercury Circle 
Littleton, Colo. 80124 

BUFFERED EXPANSION BOARD for ZX80/1 
BUFFERED EXPANSION BOARD for ZX80/1 
For marketed and user built periph¬ 
erals. All lines fully buffered and 
in same order as on Sinclair port. 
Unique decoder circuit makes avail¬ 
able up to 8K of memory mapped I/O 
addresses. Holds 6 card edge conne¬ 
ctors and has 1 set of gold fingers 
.Has many on board circuitry and 
mechanical options. Develop your 
own peripherals with wire wrap on 
readily available cards. Plans for 
I/O port, A/D, D/A, DMA, More, will 
be available soon. Write me of your 
developments so that Expansion 
Board users may benefit. Board is 2 
sided,plated holes, tin plated, 
legend, solder mask,7x8 in. All 
parts readily available. With 
complete documentation. Available 
as BARE BOARD (with connector to 
computer) or KIT (with 8 I.C.s , 
sockets,6 connectors,parts needed. 
Immediate delivery while current 
stock lasts.To order send check: 
$33...BARE BOARD, $63...KIT, to 
COMPUTER CONTINUUM, 301-16 Ave 
San Francisco CA 94118. Calif res 
add 6 l/27o tax. Send stamp for spec 
sheet/photo; write or call (415) 
7526294. EXTRA! UHF modulator $15. 
Solves VHF interference problems. 
Send to MODULATOR, same address. 
Eric Reiter 


21 



ZX81 SOFTWARE ON CASSETTE 
"Special Introductory Offer!" 
12 IK Games on cassette with copies 
of programs and full instructions: 
DEPTH CHARGE,BLACKJACK,AUTO RACER, 
MORTAR SHELL,THREE TOWERS,and more. 
All for $6. 75 '"’'*freE CATALOG with 
first order or send SASE to* H & H 
ELECTRONICS, 3379 Route 46, - 6D 
Parsipanny, N.J. 07054 

"ZX81 MONOPOLY" - Now available. 

16K RAM - imported from the UK. 
British board version family game. 
$14.95-from Savage Software, PO Box 
892, New Smyrna Beach, FL 32069 


COMPUSETTE is a C-10 cassette which 
is especially designed for micro¬ 
computer application by Tapemasters 

IN TEXAS PHONE (214) 349-0081 
FREE OUT-OF-STATE 1-800 527-1227 
VISA MASTERCARD C.O.D. 


25 FOR $20.00 
100 FOR $70.00 
500 FOR $330.00 

10% DISCOUNT FOR CASH 
MAIL CHECKS OR MONEY ORDER TO 
TAPEMASTERS-POST OFFICE BOX 38651 
DALLAS, TEXAS 75238 
FREIGHT PREPAID*DEFECTIVES REPLACED 


ZX81/80 WEATHER FORECASTER 8K 16K 
Needs a Barometer.FORCAST 36 Hrs. 
in advance.LISTINGS:$5+SASE Richard 
Toy 546 CR. 214 Fremont,OH 43420. 


V /\ /\ /\ /\ /V /\ ✓\ /\ /\ yv y\ /\ yv yv y\ yv y\ /\ yv /\ /V yv /\ y\ 

FASTEST SPACE WAR GAME YET I * 
-81 Space Raiders for ZX81 with * 
16K RAM. High speed graphical * 
display of moving starfield and * 
custom ML math package provide * 
real time, accurate simulation * 
of space navigation and battle. * 
Only $19.95 for cassette, * 
keyboard overlay, and manual. * 
NIRAD ELECTRONICS, 959 East * 
460 South, Provo, UT 84601 * 

U •kU ^»a- ..fa- ^1-. ,^1-- 

V /V y\ y\ y\ y\ yv yv yv yv yv yv yv yv yv yv yv yv yv yv yv yv yv yv yv yv yv yC /\ 


^LOTS OF GRAPHICS********** 
LAND THE SPACE SHUTTLE and LAND/AIR 
BATTLE. Two games on one tape.$8.85 
*NEW* SPACE BATTLE. On tape...$6.95 
Games for ZX81 8KROM/16KRAM*FUNWARE 
7119 Santa Fe Av. Dallas, Tx. 75223 


EDGE CONNECTORS:Solder-eye or wire- 
wrap ,gold-pltd contacts-$7.50,5/$30 
*WIRING DIAGRAMS for attaching key- 
boar ds&joy sticks to ZX81-$2. SMUG 
PROJECT,Box 13042,Ft Wayne,IN 46866 

Create GAMES to $ell! or DRAW/ERASE 
Graphics. GOOD IDEAS/INFO/FUNI Be a 
part of huge new ZX80/81 Mrkt. Send 
$2 & SASE: WSM PRODS. 4365 Ventura 
Canyon Ave. Sherman Oaks, Ca 91423 

MAXWELL'S DEM0N--an action game for 
the ZX81 with 2K RAM. Send SASE for 
details,$4 for tapes: A. Longacre, 
21 Leitch Ave, Skaneateles,NY 13152 

WORD PUZZLE-Guess phrase,title,name 
by guessing 1 letter at a time Use 
computers puzzles or opponents. 
YAHTZEE-Challenging game of skill 
+luck BOTH on cassette+instructions 
+2 more funprograms 8K/16K ZX80-81 
Send $4.95 CK or MO payable to 
A. Kohlenberg to: JAMM SOFTWARE 
1301 SR 523#37 FREMONT,OH.43420 
8K/1K WORD PUZZLE Send SASE+$1.50 

Turn your ZX81 into a full graphics 
calculator able to display equation 
with result! Short program only $1+ 
SASE: ZxCo. POB 138 Syosset,NY11791 

ZX81 T-Shirts!-Finest quality with 
distinctive ZX81 logo emblazoned on 
black field.Specify Sm,Med,Lg.$6.95 
@,Check or MO +$lper order shipping 
CUTS Co,P0 Bx 37 Mamaroneck,NY10543 


EZ ZX typing/EZ switch to regul¬ 
ar keybrd. EZ PLANS. $3.& SASE: 

WSM PRODS. 4365 Ventura Canyon, 
Sherman Oaks, CA 91423 

43 pin gold W/W edge connectors $4. 
6116 150ns RAMS $10. List of more 
items w/SASE. Postpaid from: Weick, 
7127 W. Becker Ln, Peoria, AZ 85345 


22 







FOR SALE: ZX80 ROM Switch. 
Run 8K or 4K Software at a flick 
of the switch! Basic Kit: $24.95 
Full Feature Kit: $34.95 (Includes 
keyboard beeper & load processor.) 
Marex Electronics, 2805 Abbeyville 
Valley City, OH 44280 

MAGIC SQUARE. World's Most Magic!!! 
16x16 More Magic tn BEN FRANKLIN's 
Probe with ZX. $2.00 EZRA GROUP II 
Box 5222 San Diego,California 92105 


OUR POLICY ON CONTRIBUTED MATERIAL 

SYNTAX ZX80 invites you to express opinions related to the ZX80 and the 
newsletter. We will print, as space allows, letters discussing items of general interest. 
Of course, we reserve the right to edit letters to a suitable length and to refuse 
publication of any material. 

We welcome program listings for all levels of expertise. Programs can be for 
any fun or useful purpose. We will test run each one before publishing it, but we 
will not debug programs; please send only workable listings. 

In return for your listing, we will pay you a token fee of $2.00 per program we 
use. This payment gives us the nonexclusive right to use that program in any form, 
world-wide. This means you can still use it, sell it, or give it away, and so can we. 

We will consider submissions of news and hardware or software reviews. Please 
keep articles short (350-400 words). Again, we reserve the right to edit accepted 
articles to a suitable length. We will pay 7 cents per 6 characters, including spaces 
and punctuation, for accepted articles. 

When you send in programs for possible publication in SYNTAX, please 
include the following information: 

• How to operate the program, including what to input if it does not contain 
prompts. 

• Whether you can run the program over again and how. 

• How to exit the program. 

• The Syntactic Sum (using the Syntactic Sum program in the February, 1981, 
issue). 

• Whether it fits in IK or 2K RAM (or 16K when available). 

• Whether it uses the 4K or 8K ROM. 

We pay for this explanatory text at the same rate as for articles in addition to 
payment for the program itself. 

If you want us to return your original program listing or article, please include 
a self-addressed, stamped envelope. Otherwise, we cannot return submitted material. 


SOFTWARE: Sinclair ZX81 cassettes # 
1,3,4 (new factory cass.) 12-ganies, 
3 B+H. No waiting! $27,415-387-1161 

AFRICAN PILOT:Program mixes advent¬ 
ure & business:You battle jungle to 
keep plane/profits UP:Graphics! $10 
EXCITING FLIGHT SIMULATION PROGRAM: 
Takeoff, land, outrun/dodge hazard: 
Realtime view:Plane/Instruments!$10 
HENSLEY, BOX 334,ASHEBORO NC 27203 

Load ZX80/81/MicroAce everytime-LED 
Monitor. Plans $2+SASE; Kit $6+$l 
S6cH. Hold full load Ik for 25+ 
min. or full 16k for 10+ min. if 
elec, faulters or fails. Plans $5+ 
SASE; Kit $19.95 +$1 S&H. R.H. 
Enterprises, 1408 N.4th Ave. E., 
Newton, Ia--50208. 

SOFTWARE - - - SOFTWARE 
ZX80 - ZX81 

Over 200 Programs From Physics And 
Business to Games. For IK and 16K 
List price from $.05 and Tape price 
From $2.10 

Send $ 1.00 for Catalog to: 
Detron of Hawaii 
2007 Naio Street 
Honolulu, Hawaii 
96817 

The $ 1.00 good toward purchase 


SYNTAX ZX80 is published 

monthly by a wholly-owned 
subsidiary of The Harvard Group. 

Syntax ZX80, Inc. 

RD 2, Box 457, Harvard, MA 01451. 

Telephone 617/456-3661. 

12 issues, $29. Single issue, $4. 

Publisher: Kirtland H. Olson 
Editor: Ann L. Zevnik 

Printed by Joseph E. Marhefka, Jr. 

Clinton Offset Printers 
Clinton, MA 01510 

© Syntax ZX80, Inc., 1981. All 
rights reserved. Photocopying 
prohibited. ISSN 0273-2696 


YES! Please send me 12 issues of SYNTAX for $29. 

□ My check for $29 is enclosed. □ Please charge my □ MasterCard 
Make checks payable to: □ Diner’s Club □ American Express 

SYNTAX ZX80, INC. □ VISA □ Carte Blanche account 

{ 

account number_ ’ _ 

exp. date_bank number (MC only)_ 

signature_ 

Name_Title_ 

Organization_ 

Address__ 

City_State_Zip_ 

Day Phone_(_)_Evening Phone_(_)_ 

ZX817S 

I own a □ Sinclair ZX80 □ Sinclair ZX81 Telephone orders call 

617-456-3661 


23 





FINALLY-A BATTERY BACKUP SUPPLY for 
your Sinclair or MicroAce computer. 

^1- ..»- -J^ 

/\ /\ /\ /v /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /V /\ /V /V 

''END LOST MEMORY DUE TO BLACKOUTS!'^ 

/V y'VfVrV'/VVfVoV/V/VVf Vf */V*V<-•/'<•*** 

''Built-in NiCd rechargable battery 
takes over should AC line go dead. 
''Makes your ZX80/81 truly portable 
-run for 2hrs. or more ANYWHERE! 

* Vastly improves Glitch-rejection. 
*8V pre-regulator lets your ZX run 

cooler, with less chance of damage 

*^1-. *-•- *-*-• *■*-- *-’•'* ■>•’-* *-*■* 

/\ /\ /\ /\ /\ /\ /\ /\ /\ /V /\ /\ /\ /\ /\ /\ /\ /V /\ /\ /V /V /\ /V /V /V /\ /\ /V /V /\ 

Don't get annoyed by a sudden crash 
before you order yours. Mail check 
or MO for $84.50 ppd., or send SASE 
for specs and info. Cal. residents 
add 67o sales tax. Model No. BBU-2 

-SYNCWARE COMPANY- 

4825 Elrovia Av. El Monte,Ca. 91732 
*First 50 orders or inquiries get* 
'■'FREE copy of our "Syncwars" pgm. 1* 

16K from GREAT LAKES SOFTWARE I 
All new software including games. 
Business applications and muchmore. 
Also, 16K RAM module now available 
Write for FREE catalog to: 

Great Lakes Software,201 Burlington 
Road, Valparaiso, IN 46383 

''* Double your memory ** Run longer 
Programs with easy to install kit, 
complete &•instructions only $19.95 
+1.95 - Rebates! Order today. Power 
tronix 25 E.23 Bayonne,N.J. 07002 




H\RV\RD 

GRDU^ 

Bolton Road. Harvard, Mass. 01451 



MORE GAMES FOR YOUR ZX81... 

Five IK programs.$10. 

Bandit, Chase, Life, Pong, Skeet. 


Any two 16K programs 
Bong 

Checkbook 
Solitaire 
Biorhythm 
Backgammon 
Cat and Mouse 
Guess the Animal 


.$ 10 . 

Craps 
Hangman 
Checkers 
Blackjack 
Stock Market 
Klingon Wars 
3K TicTacToe 


-- all programs on cassette tape -- 


Send check or money order to: 


BIOCAL SOFTWARE 


340 Cypress Drive 
Fairfax, CA. 94930 


ZX*ZX*ZX*ZX*ZX*ZX''ZX*ZX*ZX*ZX*ZX*ZX 
''BANTA SOFTWARE NOW HAS PACK 'EM * 
*IN MONZXER for $6.95 on tape.Gob-* 
*ble up dots,avoid goblins;for 80s* 
*or 81s.Football,Murder in the RAM* 
*Casino, and Super Monzxer on tape* 
*:$3.95 each. From our engineering* 
*dpt:Beam Design & Pipe Flow$19.95* 
*each.Coming soon:TANK SIGHT-BANTA* 
''SOFTWARE, RD#7, Bethlehem, PA 18015 * 


ZX*ZX*ZX*ZX*ZX*ZX*ZX*ZX*ZX*ZX*ZX*ZX 


V«VVf****VfVc+V<'>'oV-;V'5'oV>VV<-VoVVc'V*VoVVf*>V>V*Vc+++>V 

Need freelance help to develope a 
very low cost ZX printer. Todd 
Miles, AArtic Mfg., Inc 27 Canal 
St., Millbury, Mass. 01527. 

■/VVc/VVc /VVc/V-/V/V-/V/V -jV/V VoV */V-zV/WcVc Vc/VVcVc Vc * */V'/V'/V 


First Class 


U.S. Postage 
PAID 

Harvard, MA 
Permit No. 8 
■ 01451