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SYNTAX 


Serving 

The Timex-Sinclair Family 
Of Personal Computers 


A PUBLICATION OF THE HARVARD GROUP 


VOL.3 NO.9 


ISSN 0273-2696 


SEPT., 1982 


IN THIS ISSUE 


8K Programs 

Monthly Calendar.5 

Significant Figures 

Subroutine.16 

Beginning Programming 

ZX81 Math.8 

Classified Ads.20 

Dear Editor.12 

Hardware Review 


ZX99 Tape Controller..19 
Machine Code Programming 


Testing Bits for 

Branching.19 

Math Function Execution 

Time.16 

Maximize Display File 
for MC.5 


News, New Products..1,2,3 
Program Corrections...,17 
Program Improvements...17 
Report on the Spectrum..7 
Software Review 


Multifile.9 

Subscription Info.23 

TS1000 Test and Review..6 

TV Sync Solution..6 

Users' Groups.14 

Index of Advertisers 


Byte-Back.9 

Gladstone Electronics..15 

Memotech Corp.4 

Robin Products.16 

Softsync Inc.3 

Sinclair Research..10,11, 

18 

Zeta Software.7 


SQ, SYNTAX QUARTERLY, is 
coming in November! All 
SYNTAX subscribers get 
the first issue free. 


ATTENTION TS1000 OWNERS 

All information about ZX81s in SYNTAX 
also refers to Timex-Sinclair 1000s. The only 
difference between the machines is that 
TS1000S come with 2K RAM; ZX81s come with IK. 

BASICARE OFFERS ZX81 MEGABYTE MEMORY DECODING 

In late August BASICare of London intro¬ 
duced their Organic Micro system for ZX81s. 

It consists of stackable modules, including a 
memory mapping device to extend ZX81 address 
space to IM bytes (129.95), 2K-64K RAM 
(£19.95-64.95), 24 input/output lines 
(£22.95), ultra-low power memory backed by 
battery for nonvolatile program/data storage 
(£32.95), and more. No US dealer now, but 
you can buy direct, BASICare Microsystem 
Ltd., 5 Dryden Ct., London SEll 4NH, UK. 

ROSETTA STONE NOMINATIONS BEING ACCEPTED 

Nominations are open for the 2nd annual 
Rosetta Stone award, given for the best inde¬ 
pendent product (application, software pack¬ 
age, peripheral) for ZX/TS computers. Send 
your nominee's name, address and phone number 
to SYNTAX, RD 2 Box 457, Harvard, MA 01451 
before 31 Dec 82. This year's prize, spon¬ 
sored by Mindware Inc. of Wayland, MA, will 
be awarded by SYNTAX editors. Last year Dr. 
Ian Logan won for his 8K ROM disassembly. 

QSAVE CUTS SAVE/LOAD TIME 

QSAVE, a 2-part package, drastically 
cuts your ZX81 SAVE/LOAD time. The software 
increases the baud rate, or data transfer, of 
ZX81s to 4000, saving or loading 16K in 29 
seconds. It also provides a program verify 
to check for good save. The QSAVE hardware 
is a 2-stage amplifier/filter. $30 US in¬ 
cludes postage. Personal Software Services, 
112 Oliver St., Coventry UK CV6 5FE. 


1 






















NEW PRODUCTS AND SERVICES 

Ed. note; Unless specified, all 
ZX81-related products should work 
with Timex-Sinclair 1000 computers. 

F/22 Press has cut the price of 
their DARKSTAR darkroom program 
complete package (DARKSTAR on tape 
with documentation, ZX81, 16K RAM, 
12" TV monitor, tape recorder) from 
$550 to $475 (includes delivery in 
continental US. F/22 Press, PO Box 
141, Leonia, NJ 07605. 

NIM Electronics plans to introduce 
a ZX81 keyboard/enclosure kit in 
late September. It consists of an 
aluminum enclosure which mounts the 
ZX81 PC board and a keyboard with 
ZX81 legends on the sloping front 
surface. Assembly time, according 
to Ronald Kern, is about 20 min¬ 
utes, no soldering. Price; $150. 
NIM Electronics, 1 Denise St., 
Parlin, NJ 08859, 201/721-0070. 

Find over 600 ZX-TS products listed 
in The Sinclair Computer Family 
Sourcebook. Each listing gives a 
description, prices, computer re¬ 
quirements and suppliers' names and 
addresses. First revision, $6.95+ 
$1.25 postage, 93 pgs. New edi¬ 
tions are planned about every six 
months, according to Randy Hecht. 
Atlantic Computer Products, 5 Main 
Plaza Suite 1424, United Virginia 
Bank Building, Norfolk, VA 23510. 

Eliminate heat-related problems 
with the Power-Pack. It gives two 
outputs; a fixed +5V at 1.2 amps 
and a screwdriver-adjustable +6.5- 
+15V. It also includes a push 
button to clear the computer, a LED 
power-on indicator and the connect¬ 
ing plug and cable. Full hookup 
instructions included. The Power- 
Pack is housed in a 5x4x3" aluminum 
enclosure and the 120VAC-60Hz input 
is fused for safety. Price is 
$37.50 + $3.50 shipping. CA res. 
add 6.5% MacSwan-Packaging Co., 

POB 4697, Downey, CA 90241. 


Independent Sinclair service; 
Tercentennial Technical repairs 
Sinclair computers for a flat $35 
rate plus shipping via UPS. Your 
repair is guaranteed for 30 days. 
According to manager Jack MacGrath, 
average turnaround time is 2-3 
days. Send your machine by UPS 
with a description of the problem, 
check or mo., and your name, ad¬ 
dress and telephone number. 
Tercentennial Technical, 70 
Tercentennial Dr., Billerica, MA 
01821, 617/667-8272. 

Get ready for the office pool— 
PICK'EM predicts winning football 
teams and point spreads in the NFL 
on your 8K/16K Sinclair. On tape, 
$9.95 plus $1.50 postage. Stuart 
Software, 25381-G Alicia Pkway 
Suite 316, Laguna Hills, CA 92653. 

Norris Radio & Electronics have now 
expanded their repair services to 
the continental US (Jun.82). They 
repair out of warranty ZX81s (kit 
and assembled) and TS1000S for 
$8.50/hr plus parts. Turnaround 
time is about 48 hours. Norris 
Radio & Electronics, 144 Terry Dr., 
Slidell, LA 70458. 

ZX Hardware Team of the ZX Users 
Group of New York offers inexpen¬ 
sive 64K memories; $135 to club 
members and $150 to nonmembers, 
plus $5 postage. ZX Hardware Team, 
Box 560, New York, NY 10005. 

Winky Board cassette loader/dupli¬ 
cator interface includes LED level 
monitor, earphone eavesdropper and 
interference filter, plus circuits 
for direct-copying any ZX/TS tape 
(even programs that can't be listed 
or saved). Only 1X1.5", Winky 
Board needs no power or computer 
mods, won't interfere with extra 
memory. Info free. Assembled and 
tested, $18 ppd. Kit, $12 ppd. PA 
residents add 6%. Overseas add $2, 
pay by international M.O. in US 
dollars. G. Russell, RD 1 Box 539, 
Centre Hall, PA 16828. 


2 



Add-a-Switch is an on/off switch 
for your ZX81 or TS1000. It in¬ 
stalls instantly with no mods and 
eliminates plug and jack failure. 
Price: $14.95. Robert Downs, Lyon 

Ware, 1520 S. Lyon, Santa Ana, CA 
92705, 714/835-9512. 

Fulcrum's ZX81 Loading Aid helps 
load tapes first time. It plugs 
between ZX81 and tape recorder, 
using LED indicators to let you 
correct recorder volume. Unit with 
full instructions $21. Special 
versions for ZX80s and ZX Spectrums 
(specify when ordering). Fulcrum 
also offers ZX/Spectrum Softwear— 
short sleeved T-shirts with Sin¬ 
clair ZX81 or Spectrum lettering. 
Red on black or white, S,M,L,XL 
children's and adult's, $7. Im¬ 
proved Keyboard Bleeper gives short 
Bleep with any keypress. Unit fits 
under keyboard or ZX PC board, no 
soldering. $19. Fulcrum Products, 
Hillside, Steep Ln., Findon, 
Worthing, West Sussex BN14 0UF. 

RIP; QZX, the ZX newsletter for 
amateur radio users, is ceasing 
publication because its publisher 
can no longer handle the load. If 
you're interested in putting out 
QZX, write to Marty Irons, K2MI, 46 
Magic Circle, Goshen, NY, with "Re¬ 
placement for QZX" in big letters 
on the envelope. 

PROGRAMMING CONTEST 

Computer Engineering Services 
is sponsoring a Sinclair ZX pro¬ 
grammers' contest. First prize is 
$150, 2nd $75, 3rd and 4th a year's 
subscription to SYNTAX. Programs 
must be original and written for 
ZX80 with 8K ROM, ZX81 or TS1000, 
in IK, 2K or 16K (specify config¬ 
uration). Rewrites from other 
BASICS may be considered. Entry 
deadline is 15 Oct 82. For com¬ 
plete rules and entry forms, write 
Computer Engineering Services, The 
Jarrett Company, PO Box 1222, Show 
Low, AZ 85901. 



ZX81 &TS1000 SOFTWARE 


GRAPHICS KIT 16K 

23 exciting machine code routines that give you control over your screen as never 
before. 

Draw/Undraw - draws or deletes your multi-character shape which is defined in a REM 
statement. You may define as many different shapes as you like and draw/undraw each at 
will at whichever screen position you choose. 

Border/Unborder - Around the edges of your screen Edit lines can be used if required. 
Your border is protected when foreground is on. 

Foreground on/off - Protect existing characters on your screen. When on new shapes 
will appear to slide behind and re-emerge from other shapes. 

Reverse - converts all characters to their inverse video. 

Fill - fills any number of lines you specify, starting at any line by your chosen character 
PRINT POSITION CONTROLS 

Up, down, left, right: alter your next print position in the direction indicated. 

Editprint moves next print position to first edit line. 

SCROLL facilities 

Upscroll, Downscroll, Rightscroll, Leftscroll - scroll your screen in the direction 
indicated. 

Onscreen/offscreen - turns your screen on and off. 

Search and Replace - will search the screen for every occurence of the character you 
specify and replace it with new character. 

Backgroun on/off - fills your screen with specified character. When foreground is on 
existing information is unaffected and shapes will appear to pass in front of your 
background without deleting it. 

Square - draws a square or rectangle from your specified co-ordinate. 

All these routines are in machine code for SUPER-FAST response. Simply load 
GRAPHICS KIT, which repositions itself at the end of your RAM, and then your own 
program (or key in a new one). 

GRAPHICS KIT occupies slightly over 2K at the top of your 16K RAM and that includes 
space to load the programmer’s TOOLKIT described below. On loading, it repositions 
RAMTOP (see your ZX81 or TS-1000 manual) so it is protected from NEW and from being 
over-written by your own program. ^ 

ibK ^14.95 

PROGRAMMERS TOOL KIT 1 6K 

Line renumber - you state starting number and increment value. Free Space - tells you 
how many free bytes you have left. Search and replace - changes every occurence of a 
character as you require. 

Tape routine - provides a system WAIT condition until a signal is received in the cassette 
ear jack-has many uses! 

Special Graphics routines - Hyper graphics mode - graphics as never seen on a ZX81 
before. Fill - fills your, screen instantly with your specified character. Reverse - changes 
each character on your screen to its inverse video. All these routines are written in 
machine code! 

Also includes all the above plus: GOTO’s and GOSUB’s included in line renumber. 
Search for and list every line containing specified character. 

An incredible achievment!! 16K $14.95 


These 2 unique Toolkits are written as "compatible” and can therefore be loaded in 
together. When loading The Programmer’s Toolkit on its own the user has first to enter a 
poke code. However when used with the Graphics Kit, which is loaded first, the poke code 
is not needed. 

Buy both programs together for $25.00 


WRITE FOR FREE CATALOG 

□ Please send me copies of 
GRAPHICS KIT @ $14.95 ea. 

□ Please send me copies of 
PROGRAMMERS TOOLKIT @ $14.95 ea. 

Mastercard/VISA #_ 

Exp date_ 

Please add $1.50 shipping & handling 
New York residents add sales tax. 

SEND CHECK OR MONEY ORDER TO: 

SaFTSYlMC^IIMC, 

PO. Box 480, Murray Hill Station, New Mxk, N.Y 10156 (212) 685-2080 

Foreign orders must be paid by International Money Order or 
foreign draft in U.S. Dollars drawn on a New York bank. 

NAME 


ADDRESS. 
CITY _ 


STATE/ZIP. 


3 




BEHIND EVERY 
GOOD SINCLAIR 
ISAMEMCFAK 


If you own a Timex-Sinclair 1000 or 
ZX81 computer, you should have a 
Memopak behind it. From increased 
memory to high resolution graphics, 
Memotech has a Memopak to boost your 
system’s capabilities. Every Memopak 
peripheral comes in a black anodised 
aluminum case and is designed to fit 
together in “piggy back” fashion to enable 
you to continue to add on and still keep an 
integrated system look. 


High Resolution Graphics 




Printer Interface'^ Memopak RAM 


Order at no risk 

All Memotech products carry our 10 
day money back guarantee. If you’re not 
completely satisfied, return it in ten days 
and we will give you a full refund. 

And every Memotech product comes with a 
six month warranty. Should anything be 
defective with your Memopak, return it to 
us and we will repair or replace it free of 
charge. Dealer inquiries welcome. To order 
any Memotech product call our toll-free 
number 800/662-0949 or use the order 
coupon. 


l%lwitLn 

CORPORATION 

7550 West Yale Avenue 
Denver, Colorado 80227 
(303) 986-1516 
TWX 910-320-2917 



64KRAM 


$179.95 


109 95 


16KRAM 


59 95 


Centronics Parallel Printer Interface 104,95 


RS232 Printer Interface 


13995 


High Resolution Graphics 


144.95 


Shipping and handling 


* All prices quoted in U.S. dollars 
** Colorado residents please add sales tax 
□ Check □ MasterCard □ Visa 

Account No. _ 


Name 


Memopak 64K RAM The 64K RAM extends the 
memory of your Sinclair by 56K to a full 64K. It 
is directly addressable, user transparent, is 
neither switched nor paged and accepts such 
basic command as 10 DIM A (9000). The 
Memopak 64K turns your Sinclair into a 
powerful computer suitable for business, 
recreational and educational use. No additional 
power supply is required. 

Memopak 32K RAM The 32K RAM Memopak 
offers your Sinclair a full 32K of directly 
addressable RAM. Like the 64K Memopak, it is 
neither switched nor paged and enables you to 
execute sophisticated programs and store large 
data bases. It is also fully compatible with 
Sinclair’s or Memotech’s l6K R\M to give you a 
full 48K of RAM. 

Memopak 16K RAM The Memopak l6K RAM 
provides an economical way to increase the 
capabilities of your Sinclair. And at the same 
time, it enables you to continue to add on other 
features with its “piggy back” connectors. It is 
compatible with the Sinclair l6K or a second 
Memopak l6K or Memopak 32K to give 32K or 
48K of RAM respectively. 

Memopak High Resolution Graphics The 
Memopak HRG contains a 2K EPROM monitor 
and is fully programmable for high resolution 
graphics. The HRG provides for up to 192 by 248 
pixel resolution. 

Memopak Printer Interface The memotech 
centronics parallel or RS232 printer interface 
paks enable your Sinclair to use a wide range of 
compatible printers (major manufacturers’ 
printers available through Memotech at 
significant savings). The resident software in the 
units gives the ASCII set of characters. Both 
Memopak printer interfaces provide lower case 
character capabilities. The RS232 Interface is 
also compatible with modems. 

New products coming soon Memotech will 
soon be introducing four new Sinclair 
compatible products: a high quality, direct 
connection keyboard, a digitizing tablet, a l6K 
EPROM and a disk drive. Watch for our future 
advertisements. 













MONTHLY CALENDAR 


This 8K/16K program displays a 
calendar for any month in any par¬ 
ticular year. It uses equations 
developed by Zeller, the astron¬ 
omer, to determine the day that the 
desired month begins on. To run, 
simply type in the program, press 
RUN, and select the desired month 
and year for the calendar. This 
program accepts the data and deter¬ 
mines the name of the month (lines 
1-210). Next the program deter¬ 
mines the number of days in the 
requested month and checks for a 
leap year (lines 240-420). Finally 
the program displays the final 
calendar. To display another 
month, simply press RUN again and 
enter the necessary information. 
There are no special instructions 
for exiting; the program does so 
automatically. 


Herb Cohen, Winchester, KY 


i " 


1 REH Cni-ENDER 
S FRST 

10 PRINT "ENTER fl TO 


S© INPUT H 

3© PRINT "ENTER V fe RR" 

4.0 INPUT Y 
SO" t-ET 

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gf tSJ ="FEBRURRY 

110 hU =”HRRCH 

hiT g$ t4.3 ="npRXL 

111 hi! g$«Si*"MRY 

iSi ="-«UNE 

iSg ^^t7>="vJULY 

iRra ="HUGLfST 

9©© g* =**OCTOBER 

«ia L^ 9f J ="*^0^EHBER " 

ail DIH R?i|f ^“"OECEHBER " 

S3© LET END=30 

iMi ss^s 5 .«si gs.r-i„gs [^1 

ill 

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^|10 IF H=i QR M=2 then LET M=M 
^,320 IF H=13 OR H = 14. THEN LET Y 


34.© LbT NUHrs CRy*? — XNT 1 

LET NUH=1NT (NUH^.:ijr ' ^ ^ ' 

let 3TRRT=NUH 

START =7 

FOR R=STRRT TO 4-2 
LET A tPJ =DAY 

l et DAV=& AY+1 
next P 

CLS 

PRINT TAB 10;A$(NON) ; "B";YE 


35© 
35© 
37© 
33© 
3Q© 
4.0© 
4.x© 
4.^© 
4.3© 
4.4.0 
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SUN HDN TUE UED 


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45© PRINT 
45© PRINT “ 

THU PRX SRT" 

4.7© FOR R=© TO 5 
4 . 5 © FOR 0=rXi-R^T TO 
^©0 CXC:=^-^R^T 

TAB C4. 

A<c.t=0 then goto 5S0 

THEN PRINT TAB 

53© IF A«C>>END THEN 


54.0 PRINT TAB 
S5© NEXT C 
56© NEXT R 
57© STOP 
SYrTTACTIC SUM: 


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55© 


issea .. SK 


MAXIMIZE DISPLAY FILE FOR MC 

I upgraded my ZX81 to 2K of 
RAM. Lately I have been interested 
in programming machine code dis¬ 
plays. The problem is that since 
my machine has only 2K RAM it al¬ 
ways sets up a minimal display 
file. (See ch.27 p.l29 in the 
BASIC manual.) To do any kind of 
MC display you cannot have a mini¬ 
mal display file. I used to use a 
short routine that would PLOT a 
line up the right side of the 
screen. This "opened" the display 
and allowed a MCD. This was slow 
and tiresome to do. 

I remembered the BASIC manual 
states that if you had more memory 
you could POKE RAMTOP lower than 
3.25K to fool CLS into setting up a 
minimal display file. So I figured 
why not go the other way, that is, 
POKE RAMTOP higher than 3.25K to 
fool CLS into a full display. It 
worked! I have used my computer for 
a while this way and no crashes or 
problems whatsoever. 

The procedure for POKEing 
RAMTOP is somewhat different than 
the manual states: once you power 


5 




up, POKE 16389,78 and then CLS. 

Wait for a moment and voila, cursor 
and a full display. (To verify 
this, try POKE 16520,6.) 

Remember, a full display will 
occupy 793 bytes of RAM. This may 
be no good for IK machines. Also 
if you execute a NEW you must re- 
POKE RAMTOP to get a full display 
again. You can switch between 
minimal or full display file by 
POKEing RAMTOP at any time during 
programming. I use POKE 16389,72 
for a minimal display and POKE 
16389,78 for a full display. 

John Guineau, Marlboro MA 
TV SYNC SOLUTION 

If your ZX81 display has dim 
lines and horizontal distortion 
moving up or down the screen, it's 
not synchronizing with the TV hori¬ 
zontal sweep. A simple component 
change on the Sinclair circuit 
board will solve the problem. 

Here's what's happening: The 
ZX81 uses a 6.5 MHz ceramic filter 
as the frequency-determining ele¬ 
ment in the oscillator (clock). 

The filter is loaded with a 100 pF 
capacitor (C6) to reduce the 
frequency to about 6.3 MHz. When 
the Sinclair Logic IC divides this 
down, the TV horizontal sync 
frequency (15750 Hz) is obtained. 
The tolerances on both the ceramic 
filter and the capacitor are large 
enough to produce a sync frequency 
that may be outside the lock-in 
range of the TV horizontal sweep 
circuit. If the sync frequency 
produced by the computer is too 
high, the lines move down; if too 
low they move up. To correct the 
situation and get stable lock, just 
change the value of C6. To reduce 
the frequency, increase C6. Tack- 
solder small-value capacitors 
across C6 on the bottom of the 
circuit board. Start with a 10 pF. 
Increase it until the lines disap¬ 
pear. Trim the leads on the final 
capacitor to about 3/4 inch, insu¬ 


late them, permanently solder the 
capacitor, and position it parallel 
to the board. If the frequency is 
low, you'll have to replace C6. 
Substitute a 10-20 pF capacitor to 
make the frequency too high, then 
follow the preceding steps. 

In my case, the horizontal 
sync frequency was about 15600 Hz. 

A new C6 value of 57 pF locked the 
sync in solidly. 

Larry Forman, Santa Barbara, CA 
TSIOOO TEST AND REVIEW 

Syntax bought a Timex-Sinclair 
1000 and TS1016 (16K RAM pack) from 
a discount house. (We have a par¬ 
tial list of Timex computer out¬ 
lets. If you can't find one, call 
us.) The prices weren't discounted 
—$99.95 for the computer and 
$49.95 for the RAM. 

Our TSIOOO performs flawless¬ 
ly, even running continuously for 
24 hours. Our RAM pack developed 
occasional crash problems after a 
few hours. We saw symptoms such as 
numeral 4 and graphic symbols on 
the display followed by system 
crash when we pressed BREAK, and 
unrecoverable loss of display sync. 
Another RAM brought by an acquaint¬ 
ance would not execute its startup 
routine. Our RAM healed itself, 
and has shown no problems for days. 

Timex provides a 1-Amp power 
pack with low ripple and heating. 

With the TSIOOO comes a 3- 
program starter tape. It loads 
easily, but poorly introduces TS 
capabilities. The programs are 
Life (esoteric math simulation). 
Maths (arithmetic test program) and 
Averages (mean and median demo). 

All run in IK RAM. Life crashes in 
16K, and the directions should say 
press X, not C, to clear. 

Instructions (in minute type) 
are unclear (for example, press 
newline after each entry—key is 
labeled ENTER). Tell friends who 
buy TS machines to read the manual 
before trying the starter tape. 


6 


A REPORT ON THE SPECTRUM 


MEH 5 ZX81 16K. RRM MEEW !! 


Sinclair's new color machine, the 
Spectrum, has been available in the 
UK for several months; no word when 
it will cross the Atlantic.—AZ 

The Spectrum is a ZX81 that 
has been developed by adding a hi- 
resolution display, color board, 
improved cassette interface and 
larger keyboard. These features 
are available to ZX81 owners but 
increase the cost considerably and 
make the fragile ZX81 more diffi¬ 
cult to use. Now they are stand¬ 
ard, giving the Spectrum a robust¬ 
ness sorely lacking in earlier 
Sinclair models. 

Drawbacks? Again the keyboard. 
Despite its improved nature, it is 
still a small calculator type key¬ 
board and not for fast typing. And 
the display has only 768 color 
areas, clearly a compromise. 

Comparing the operating sys¬ 
tems of the ZX81 and the Spectrum, 

I find several fundamental changes. 
No longer is the display produced 
in software. The ULA is mainly 
responsible for scanning the 6K of 
memory (block 4000-57FFh) that 
holds the bit pattern for the 
memory-mapped display. This scan¬ 
ning is done between Z80 access 
periods. The ULA also scans the 
"attribute area." This 0.75K area 
of RAM (block 5800-5AFFh) holds the 
color information for the 768 char¬ 
acter areas of the display. Each 
attribute byte can describe 1 of 8 
"ink" colors, 1 of 8 "paper" col¬ 
ors, 1 of 2 brightness states and 
flash-on or flash-off. The names 
"ink" and "paper" are generally 
considered "foreground" and "back¬ 
ground" on other machines. Over¬ 
all, the Spectrum has 16 colors if 
you consider the bright colors 
different from the normal colors. 

No longer is the keyboard 
scanning done in the display rou¬ 
tine. Now the maskable interrupt 
system scans for key presses every 
l/50th (UK) of a second and enters 


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base is for the 82-83 season,. 

S P e c i f y C 0 L. L. E G E o r P R 0 v e r s i ci ti „ 
Money Order 9et;ir.- rush del i'i.,'ery „ 

REVERSI by Peter Ulrich 
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the appropriate value into the 
system variable LAST_K. 

No longer are the input/output 
routines almost inaccessible. Now 
the appropriate routine addresses 
are available as "channel informa¬ 
tion," which is in effect a vector 
table in RAM. 

But what is the same? 

The BASIC interpreter is vir¬ 
tually untouched. The new features 
(multiple statement lines, multiple 
INPUT lines, the provision of READ, 
DATA, RESTORE and DEF FN); have just 
been melded in. The floating-point 
calculator is also much the same as 
in the ZX81. But there is some 
integral arithmetic and FOR-NEXT 
loops using integers run 20% faster 
than otherwise. The cassette for¬ 
mat is also the same insofar as 
there are no parity bits or check¬ 
sums. But the new standard is most 
impressive and allows for programs, 
arrays and blocks of code. 

Ian Logan, Skellingthorpe, UK 


7 








BEGINNING PROGRAMMING—ZX81 MATH 

Computing newcomers often face new 
terminology. This article expands 
on bits, bytes and binary numbers 
over the ZX81 and TS1000 manual. 

An elementary understanding of 
the mathematics involved with your 
computer will help you get the most 
enjoyment and use out of it. Your 
computer is a digital machine, or 
"number cruncher." When you press 
a key, whether it is an alpha char¬ 
acter (letter), graphic symbol or 
numeral, it is immediately con¬ 
verted to a numerical value. If 
you hate math, don't quit yet— 
we'll start at the beginning. 

When we count up from 1, we 
run out of single digits after 9. 

So we go to double digits. The 
number 10 means one ten and no 
ones; 11 means one ten and one one, 
and so on. You understand the 
meaning of each digit by its posi¬ 
tion in the numeral. 

Let's look at the numeral 
6382, read six thousand three hun¬ 
dred and eighty-two. We can break 
it down like this; 

6382=(6*1000)+(3*100)+(8*10)+(2*1) 
The number 1000 is the same as 
10x10x10, or 10 cubed. It can be 
written symbolically as 10^ (10 
raised to the third power). The 3 
in 10^ is called the exponent and 
is written to the right and above 
the number being raised. Since we 
cannot enter an exponent this way 
on the ZX81, the symbol ** (shifted 
H) is used, eg., 10**3. We can now 
write the equation for our number 
using exponents; 

6382=6*10^+3*102+8*101+2*10^ 

As you see, 10 raised to the zero 
power equals 1. Try it on your 
computer (PRINT 10**0). So our 
usual number system consists of 10 
digits and is based on 10 raised to 
a power, said to be base 10. We 
call this system DECIMAL, or more 
correctly, DECIMAL NOTATION. 

Your computer consists of 
thousands of transistors used as 

8 


electronic switches. A switch has 
only two positions, on and off. So 
the number system used to express 
what's happening within the compu¬ 
ter is quite different from the 
decimal notation we are used to. 
Because a switch has only two 
states, we need only two digits, 0 
and 1, and our number system will 
be base 2. This system is called 
BINARY. A Binary digiT is called a 
bit. Let's take the 4-bit binary 
number 1101 and express it in ex¬ 
ponential form as we did to the 
decimal number. Remember that a 
binary number is in base 2. 

1101 =( 1 * 2 ^)+( 1 * 22 )+( 0 * 2 ^)+( 1 * 2 ®) 

= 1*8 + 1*4 + 0*2 + 1*1 

= 8 + 4 + 0 + l 

= 13 in decimal 

By putting a binary number in ex¬ 
ponential form we can convert it to 
its decimal equivalent. But how do 
you go from decimal to binary? If 
you don't have a computer program 
to do it for you, you can use the 
method of succesive subtraction of 
powers of two. The name is the 
worst part. Let's take the decimal 
number 13. Start by finding the 
largest power of 2 that will divide 
into 13. Then divide the remainder 
by the next lower power of 2; 

2^=16 13/16 Too Big . ^ « 

2 '^ 2 ^ 2 "^ 2 ^ 

2^=8 13/8=1 remainder 5 1 
2^=4 5/4=1 remainder 1 1 

2;:=2 1/2=0 remainder 1 0 

2®=1 1/1=1 1 
So decimal 13= binary 1101. 

The Z80 microprocessor chip 
used in the ZX81 and TS1000 is an 
8-bit device, meaninvg that it can 
handle 8 binary digits of data at 
one time. This grouping of 8 bits 
is called a byte. So we can say 
that each memory location in our 
computer is a byte wide. When we 
express a byte in binary notation, 
it is customary to write all 8 
bits, even though there are leading 
zeros. For example, binary 1 is 
written as 00000001. 

William Wentz, Rio Rancho, NM 




SOFTWARE REVIEW 

Product: MULTIFILE—A Data Storage 

System 
Price: $29.95 

ROM/RAM required?: 8K/16K 
Printed listing?: No 
Program listable?: Yes 
Screen prompts?: Yes 
Easy to Load?: OK 
Display?: Very good 
From: Gladstone Electronics, 1585 

Kenmore Ave., Buffalo, NY 14217 

Multifile arrives with the 
program tape, 10 pages of photo¬ 
copied instructions, 3 blank tapes, 
and a 4-tape cassette album. The 
instructions are lengthy, but 
thorough. You should have no prob¬ 
lems operating the program or 
understanding its structure after 
reading these pages carefully. 

Multifile is menu-driven. You 
set up the parameters of whatever 
files you care to make. After 
completing the setup the files are 
dimensioned and you are ready to 
go. The menu lists the number of 
available files in the upper right 
corner, so you always know how much 
space is left. 

You can call up the files by 
any item in the file as well as by 
number. Once a file is on the 
screen, you can copy it to the 
printer, continue searching for 
another file with the same key, or 
return to the menu. 

One of the program's most in¬ 
teresting features is the "security 
lock." It is a two-letter key to 
enter the program. You must press 
the code in order and at the right 
interval to enter the program. 
Without the code, you cannot enter 
at all. If you have something to 
keep confidential, this program is 
for you. 

I found the program tape balky 
to load, but once finally loaded 
and copied onto my own tapes, it is 
easily retrievable. There is one 
big note to make. The C-10 tapes 
sent with the program are not long 



$ 59 « 


95 


64K MEMORY 
M-64 

129.95 WIRED & TESTED 
IN STOCK. SAME DAY SHIPMENT 
All Standard features included, plus lower 8K 
of RAM can be disabled in 2K segments to 
allow PROM or peripherals to be added. 

EXPAND YOUR 16K SYSTEM 

If you have a Sinclair 16K RAM module and need 
more memory, expand it to 32K and beyond by using 
BYTE-BACK M-16 MEMORY MODULES. 

You can’t connect two Sinclair 16K RAM modules together, 
but you can connect one Sinclair 16 K and one or more BYTE- 
BACK 16K modules to get all the memory you need 

THOUSANDS IN USE WITH PROVEN RELIABILITY 

M-16 $59 .95 $69.95 wired and tested. 

_IN_STpCK. SAME DAY SHIPMENT 

BB-1 Control Module, with S relays, 8 leds 

& 8 inputs. $59 Kit. $69 wire and tested. 
_[N_SIOCK! SAME DAY SHIPMENT 

ImODEM with RS232 Port. $99.^^ $ii995wire 


*Kit 


& tested. 


90-Day Warranty On All Modules. 
10-Day Return Privlledge 
ORDER PHONE 803-532-5812 

Add $4.95 shipping & handling to all orders. 

BYTE-BACK CO. CHECKS 

Rt. 3 Box 147 Brodie Rd. 

LEESVILLE, SOUTH CAROLINA 29070 


enough to record the program once 
it is dimensioned. They will hold 
12-13K, but not the full 16K. 

Multifile can be listed and 
modified. I made several small 
changes in the program for some 
specialized applications. My 
favorite changed the menu to not 
only tell you the files left open, 
but to tell how many you used, how 
many are left, and the total avail¬ 
able. This can be done by changing 
only one line. 

In summary, I found the program 
useful for a variety of applica¬ 
tions. The security lock was a big 
plus, and, since it can be listed 
you can learn from the program as 
well. It is well worth the invest¬ 
ment of $29.95. 

Michael Roberts, Des Moines, lA 

Our Multifile tape has 1 copy each 
side. One loaded; one didn't. 
Gladstone always replaces defective 
tapes.—AZ 


9 



ZX8I 


€0IT» ^ THEM M tO m 

1 qI 2 am 3 am 4 q| 5 c 


h Di 


PLOT UNPLOT REM RUN RAND RETURN IF 


INPUT POKE PRINT 


ffif» OR* STEFW Cem OW W S V ^ . 

QalWnlEEilRalTeilYfilu 11 lo IP 


SIN COS TAN iNT RND STRS CHRS CODE PEEK TAB 

NEW SAVE ; DIM FOR GOTO GOSU8 LOAD LIST LET 


iPRIMT H SLOW j 



ARCSfN ARCCOS ARCTAN SON A8S SOR VAL LEN USR 

copy CLEAR CONT CLS SCROLL NEXT PAUSE BREAK 


SHIFT 


fz lx fc’fv ^Ib In 1 m "1 1 


SPACE 



Introducing the 
Sinclair ZX81. 

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

The Sinclair ZX81 
is the most powerful, yet 
easy-to-use computer 
ever offered for any¬ 
where near the price: 
only $99.95* completely assembled. 

Don't let the price fool you. The ZX81 has 
just about everything you could ask for in a per¬ 
sonal computer. 

A breakthrough in personal computers. 

The ZX81 is a major advance over the origi¬ 
nal Sinclair ZX80-the first personal computer to 
break the price barrier at $200. 

In fact, the ZX81 's 8K extended BASIC offers 
features found only on computers costing two or 
three times as much. 

Just look at what you get: 

■ Continuous display, including moving graphics 


■ Multi-dimensional 
string and numerical arrays 

■ Mathematical and scien¬ 
tific functions accurate to 
8 decimal places 
■ Unique one-touch entry 
of key words like PRINT, 

RUN and LIST 

■ Automatic syntax error 
detection and easy editing 

■ Randomize function 
useful for both games and serious applications 

■ 1K of memory expandable to 16K 

■ A comprehensive programming guide and 
operating manual 

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. It comes with a 
comprehensive programming guide and oper¬ 
ating manual designed for both beginners and 
experienced computer users. And you can use 
a regular cassette recorder to store and 
recall programs by name. 



Sinclair technology is also available in Timex/Sinclair computers 
under a license from Sinclair Research Ltd. 




















Order at no risk.** 


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

And if you have a problem with yourZXSI, 
send it to Sinclair Research within 90 days and 


These numbers are for orders only. If you just 
want information, please write; Sinclair Research 
Ltd., 2 Sinclair Plaza, Nashua, NH 03061. 

*Plus shipping and handling. Price includes connectors for TV and cassette, AC adaptor, and 
FREE manual. 

* * Does not apply to 2X81 kits. 





we'll repair or replace it at no charge. 
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 
$79.95.* It's the same, full-featured computer, 
only you put it together yourself. We'll send com¬ 
plete, 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. 

A leader in microelectronics. 

The ZX81 represents the latest technology in 
microelectronics. More than 10,000 are sold 
every week. In fact, the ZX81 is the fastest selling 
personal computer in the world. 

We urge you to place your order for the 
ZX81 today. 

To order. 

To order, simply call toll 
free. Or use the coupon below. 

Remember, you can try it for 
10 days at no risk.** The sooner 
you order, the sooner you can 
start enjoying your own 
computer. 

Call toll free 800-543-3000. 

Ask for operator #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 MasterCard 
or VISA ready. 


NEW SOFTWARE: Sinclair has 16K MEMORY MODULE: Like 

published pre-recorded pro- any powerful, full fledged corn- 
grams on cassettes for your puter, the ZX81 is expandable. 
ZX81. We're constantly coming Sinclair's 16K memory module 
out with new programs, so we'll plugs right onto the back of 
send you our latest software your ZX81. Cost is $49.95, plus 
catalog with your computer. shipping and handling. 


Amount 


Ad Code09SX0S 


MAIL TO: Sinclair Research Ltd., 

One Sinclair Plaza, Nashua, NH 03061 


Name. 


Address. 


11.5, dollars 


ZX81 ! 

$99.95 


ZX81 Kit 

79.95 


16K Memory Module 

49.95 


Shipping and Handling 

4.95 


total! 












DEAR EDITOR 


Brian O'Brien of Weston, MA, 
suggested keeping the TV away from 
the recorder to avoid picking up 
the TV's 15KHZ noise. To lengthen 
my SAVE and LOAD cables, I got two 
36" long stereo cables with RCA 
plugs at both ends. I clipped off 
the plugs and added miniature 
plugs. At 36" I have no more ISKHz 
hum! The cables are shielded and 
help prevent outside interference. 
Be sure to solder the center core 
of the cable to the center lug of 
the miniature plug. I put black 
electrical tape on one to distin¬ 
guish it from the other. 

The female connectors inside 
the computer are just not strong 
enough to hold plugs firmly. When 
you move cables, computer or recor¬ 
der, one or more of the plugs may 
come out—usually the power plug! 
Wind a tiny strip of masking tape 
around plug bases. You'll need a 
bit more pressure to get the plug 
in and out. This is a cheap and 
dirty alternative to replacing the 
female connectors as Ron DeBalko 
suggested (Jun.82). 

Steve Schowiak, Hielbronn, Germany 


I read with trepidation about 
others' problems with system 
crashes, TV interference, glitches, 
overheated voltage regulators, ex¬ 
cessive line ripple and so on, but 
I didn't expect every one of those 
to appear at my doorstep the day my 
ZX81 arrived. My solution was to 
spend $19.95 to build a regulated 
0-15V, 1.5 amp external power sup¬ 
ply, available in kit form from 
Jameco Electronics, Belmont, CA 
94002. I haven't had a glitch or 
crash since and can run my ZX81 
over 16 hours with stacked RAM 
packs (for 32K), even though cur¬ 
rent drain reaches 700-800 ma with 
stacked RAMs. Try that with Sin¬ 
clair's power adapter! Jameco 
gives exceptional service. In¬ 
stock items take less than 10 days. 


even if you pay by personal check. 

I cured the TV interference 
by using ordinary coax TV cable 
properly terminated with a 50 Ohm 
resistor. I now hook up directly 
into my TV through the 50 Ohm coax 
connector, by-passing Sinclair's 
antenna switch. Voila, a display 
that is actually readable. 

Joseph Dominiecki, Wisdom, MT 


I hope no one got electrocuted 
following Martin Oakes' suggestion 
to connect their wrists directly to 
earth ground in his Simple 4K-8K 
ROM Switch (Jul.82 p.8). Static 
damage is a real danger. However, 
the human body acts like a 60 pico- 
Farad capacitor for static electri¬ 
city and all that is needed is a 
resistive path to ground to bleed 
off static charge. Place a 200K-1 
megohm resistor (1 watt carbon 
comp—big for mechanical strength) 
in series with the ground wire. 
Likewise connect exposed metal or 
conductive mats to earth ground 
through the same or similar resis¬ 
tors to drain static charge without 
shock hazard. A short stroll 
across a carpet can build up 10000- 
50000V charges on a body. When the 
relative humidity is over 60%, this 
charge dissipates slowly through 
the air. When the RH drops below 
30% the charge lingers. A 1 megohm 
wristat drops that to 100V in 
l/10th second or less. Field ef¬ 
fect devices (CMOS, J-FETS, MOS- 
FETS) and some bipolar devices fail 
with voltages (on 60 pF) as low as 
100V. So protect that RAM or ROM, 
but don't wipe out the user! 

Dave Rogers, Santa Barbara, CA 


Is it possible to merge sever¬ 
al utility programs from cassette 
to ZX81? I'd like to load a renum¬ 
ber program and an input program 
(replacing READ, DATA, RESTORE) 
before entering a new program. 


12 


Ross Shuping, Greenville, NC 


The Data-assette ZX99, reviewed 
this issue, lets you do this. To 
do it with software, check out 
Siriusware's classified ad this 
issue.—KO 


Between the 8K ROM and the RAM 
is 8K of "dead space." Is it pos¬ 
sible to put more RAM in that area, 
or even an EPROM? Or does Sinclair 
have other plans for this area? 

Dave Straub, Petaluma, CA 

Memotech's 64K RAM puts 8K in this 
space. The CAI/0 board and Data- 
assette's ZX99 use ROMs here, as do 
a myriad of other manufacturers. 

We know of no Sinclair plan to use 
addresses 8K-16K on ZX81s. You can 
place your own EPROMs in here. 
Memotech plans to sell blank EPROMs 
this fall (Aug.82).—KO 


As you know, there is a multi¬ 
tude of ZX81 software in all areas. 
To choose among the array, I'd like 
to suggest that manufacturers show 
a screen display in their catalogs. 
It's easier to visualize a program 
with sample video. 

Mark Rogstad, Wheaton, IL 


I have a ZX81 with Memopak 64K 
RAM. Normally, even with RAMTOP 
and the machine stack at 65535, you 
can enter only about 15K of BASIC 
lines. Entering more lines causes 
a crash when the top of the display 
file (VARS minus 1) reaches 32768 
(8000 hex). I found if I move the 
entire display file beyond 8000h in 
a single operation in FAST mode, I 
can add another 16K of BASIC lines 
for a total of about 31K. 

You can do this easily with a 
method like Frank O'Hara's (Aug. 
82). Insert, say, a 2K-long dummy 
REM line into a program containing 
14-15K of BASIC. Once you have 
added another 2K of your BASIC 
program you can safely delete the 
dummy REM line; as long as the 
lower end of the display file 


(D_FILE) does not drop below 8000h 
during subsequent editing, the 
system runs perfectly. In other 
words, the display hardware can 
handle the file when it is entirely 
between 4000 and 8000h or between 
8000 and C000h, but not when it is 
partly in one block and partly in 
the other. This trick doeb not 
seem to work beyond 48K (C000h). I 
don't know if other brands of 32K+ 
RAM will behave similarly. 

When you have a long REM line 
in a program, it's a good idea to 
put another line of only a REM 
right after it. Attempting to 
delete the line immediately follow¬ 
ing one that is too long to fit on 
the screen causes a system crash. 

Peter Ulrich, New York, NY 


After much frustration trying 
to share my recorded programs with 
a ZX81-toting friend, i discovered 
the alignment of the recording head 
of my Panasonic mini had gone 
askew. It was merrily recording at 
its own crazy angle, oblivious to 
all that is universal and expected 
of a machine of the eighties. 

No problem to correct it—an 
adjusting screw is generally vis¬ 
ible with the recorder in PLAY mode 
and the tape door open. With a 
small screwdriver, adjust the head 
angle to give the loudest sharpest 
sound when playing back a program. 
This method may help coax an old 
recorder into service. 

Tom Gill, Milwaukee, WI 


Last May 14, Bob Swann (and 
later a voice named Carol) of CAI 
Instrumemts promised to send me 
detailed information about various 
CAI products. It is 13 weeks since 
my request—no info. 

Ever hopeful, I ordered the 
CAI/0 board and 40-column printer 
June 7 with shipment promised in 4 
weeks. Many weeks and calls to CAI 
later, no printer and no word from 
CAI. An order accepted is a con- 


13 



tract to deliver. I get only prom¬ 
ises and not performance. After 
nine weeks and no cooperation, I 
believe your readers deserve to 
learn the truth about CAI and its 
misrepresentations. 

Christopher Bannister, Hopewell, NJ 

Carol from CAI agreed that your 
order was delayed beyond the origi¬ 
nal shipment date. This was be¬ 
cause of CAI's backlog replacing 
Widgets with CAI/0 boards and 32- 
column printers with 40-column 
printers. CAI had problems meeting 
manufacturing deadlines and have 
hired another company to make their 
products. Carol emphasized that 
CAI does not make promises they 
know they cannot keep; she recalls 
saying she would try to get your 
order out each time you called. 

She added they are very aware of 
their shipping problems and are 
working to correct them. Your 
printer went out UPS on 3 Aug.—AZ 


We all have ordered software 
and hardware from vendors inter¬ 
ested in collecting our money for 
frequently shoddy merchandise who 
hope they never hear from us again. 
I found the opposite with CAI In¬ 
struments and Bob Swann. I pur¬ 
chased over a period of time both 
the original 32-column printer and 
the new 40-column printer. Being a 
tyro in this field, I must have 
called Bob a hundred times, fre¬ 
quently on weekends. I found him 
extremely courteous, cooperative 
and helpful in explaining to me the 
arcane aspects of computer opera¬ 
tions. My last experience involved 
a broken pin on the 20-pin plug 
connecting the printer and CAI/0 
board. Within 3 days of my call, 
two replacement ribbons arrived. 

If someone gives an award for best 
equipment support in the field, I 
will be happy to nominate CAI 
Instruments and Bob Swann. 

Peter Danes, New York, NY 


USERS' GROUPS 

Here's our latest list of ZX-TS 
users' groups. To check for a 
group in your area not listed here, 
call or write us (please include a 
self-addressed, stamped envelope) 
and we'll tell you of any group 
we know of. To list your group, 
call or drop us a line and we'll 
refer interested people to you. 
SYNTAX, RD 2 Box 457, Harvard, MA 
01451, 617/456-3661.—AZ 

Santa Cruz, CA; Marc Reinig, High 
Score Video Arcade, 2301 Mission 
St., Santa Cruz, CA 95060. 

Petaluma, CA; Michael & Susan 
Degsive, 129 Saratoga, Petaluma, CA 
94951. 

Laguna Hills, CA: William H. 

Brown, 5122 Brazo, Laguna Hills, CA 
92653, 714/830-7628. 

Provo, UT; Quint B. Randle, 255 N. 
1600 West #76, Provo, UT 84601, 
801/377-4757. 

Lincoln, NE; Patrick Murphy, 4903 
Walker, Lincoln, NE 68504, 402/464- 
8086. 

Kansas City, MO; Peter B. Wolcott, 
305 W. 51st Terr., Kansas City, MO 
64112, 816/753-8546. 

Slidell, LA; Gulf Coast Sinclair 
Users' Group, 144 Terry Dr., 
Slidell, LA 70458. 

Nashville, TN; William Tracy, 3220 
Lakeland Dr., Donelson, TN 37214, 
615/889-6668. 

St. Albans, WV; Sinclair Super 
Group, William Meclow, 949 Brier 
St., St. Albans, WV 25177. 
Palatine, IL: Diana Wright, 2170 
Oak Brook Cir., Palatine, IL 60067, 
312/934-9375. 

Milwaukee, WI; Bob Harris, 2604 N. 
Murray #203, Milwaukee, WI 53211, 
414/963-9675. 

Newport News-Williamsburg-Hampton, 

VA; Jim Langston, 146 Hawthorne 
Dr^, Newport News, VA 23602, 
804/877-3920. 

Hopewell Jet., NY; Mid-Hudson 
Users' Group, Fr. Bruce 0. Bowes, 
Church of the Resurrection, Hope- 
well Jet., NY 12533, 914/226-5727. 


14 


GLaOSTOnE- ^LECTROmCS GiaOSTOnE- -ELECTROmCS GLaOSTORE- -ELECTROmCS GLaOSTOnE-yELECTROniCS GLaOSTOnE-'i-ELECTROniCS GLaoSTORE- rELECTROmCS GiaOSTORE- -ELECTRORICS 



with Quality Hardware and Software 
from Gladstone Electronics 


Cet serious a^ut ZXtti 

& 15 loaa com^itiiw^ 


Cassette Software 


DATA STORAGE SYSTEM 


ZX81 Professional Keyboard 
and Case 

A full-sized professional keyboard for the ZX81 Features 
47 keys and a full-sized space bar. Connects to the ZX81 
with no soldering required, via a plug-in flexible connec¬ 
tor. You can purchase the keyboard only, or the optional 
metal case that holds both keyboard and ZX81. Expan¬ 
sion devices (i.e. RAM packs, etc) connect to the ZX81 
edge-connector which extends from the rear of the 
cabinet. 

A professional keyboard makes program entry easier 
and less error-prone. 

Keyboard (KB-1).$85.00 

Metal case for keyboard 

and ZX81 (MC-1).$25.00 


PLUS 


32KRAM 


Machine Code Monitor and Disassembler 

ZXBUG is a powerful tool for machine language pro¬ 
gramming. It is 4K long and uses memory from 71EO to 
the top memory. ZX BUG works in hexa¬ 
decimal (base 16), not decimal, so all addresses are a 
maximum of 4 Hex bits long. Provides a total of 28 com¬ 
mands. 

Artie $14.95 


ZX 

A55EMBIER 


Data Storage System 

An amazingly versatile multi-purpose filing system for 
the 16K ZX81. The program is menu-driven, and number, 
size and headings of files are user-definable. Both string 
and numerical files are catered for. Files may be 
created, modified, replaced, and searched, and are pro¬ 
tected by an ingenious foolproof security system. Out¬ 
put to the ZX printer is aiso provided. The program 
comes on cassette, together with three quality data 
cassettes for file storage, and comprehensive documen¬ 
tation, describing a host of applications for both 
business and personal use. Supplied in an attractive 
storage case. If your ZX81 is bored with playing games, 
then this program will give it plenty to think about! 


with “piggy-back” feature 


This Machine Code program occupies 7K of memory 
and locates itself at the top of memory. The program is a 
full Editor/Assembler and Monitor. Labels may be used 
instead of any string. The features include Line Inser¬ 
tion/Delete, Insert Characters, Auto Repeat on all keys. 
The monitor has facilities to inspect memory, registers 
and run machine code programs. 

Artie $14.95 


A sensible choice for 16K RAM owners. Jigsaw 32K RAM 
‘piggy-backs’ onto your 16K RAM to give a total memory 
of 48K! If you do not own a 16K RAM, you may use a 32K 
RAM instead. At a later date you may add the ZX81, 
TS1000, or Jigsaw 16K RAM, should you decide you re¬ 
quire more memory. 

A very useful, unique Jigsaw memory feature is the pilot 
light showing if your ZX81 computer/memory is 
powered. 

Larger memory enables longer programs and greater 
data bases, enhancing the value of your personal com¬ 
puter. And the Jigsaw 32K is parf of a fully compatible 
ZX81 and TS1000 system of add-on products. Additional 
exciting Jigsaw products to follow shortly! 


The Complete ZX81 
and TS1000 Library! 


9 Powerful New Functions! 

RENUMBER. This routine renumbers a program in any 
step and from any line up to 9999 
DELETE. This command deletes a group of lines in a pro¬ 
gram. 

MEMORY. Prints how much spare memory is available. 
DUMP. Displays current values of string and numerical 
values, except arrays. 

FIND. Will find any string of up to 255 characters and list 
each line containing that string. 

REPLACE. Replaces any string of up to 255 characters 
by any other string. 

SAVE. Transfers program in computer to below RAM- 
TOP. 

APPEND. Allows two programs to be joined. 

REMKILL. Removes all REM statements from a program, 
otherwise leaving it unchanged, preserving memory. 

Artie $14.95 


The Complete ZX81 Basic Course. 

Basic Course Cassettes (2). 

Getting Acquainted with your ZX81. 

ZX81 Pocket Book. 

Making the Most of Your ZX81. 

Computer for Kids, ZX81 Edition. 

Explorers Guide to the ZX81. 

ZX81 Companion. 

^9 Exploding Games for the ZX81 . 

Not Cnly 30 Programs for ZX81 : IK. 

Machine Language Made Simple for Sinclair 

Mastering Machine Code on your ZX81 . 

ZX81 Rom Disassembly: Part A. 

ZX81 Rom Disassembly: Part B . 

Understanding your ZX81 RDM . 


Expands the ZX81’s memory capacity to its maximum. 
Use instead of 16K RAM. Same features as other Jigsaw 
memory products including pilot light and full com¬ 
patibility with other upcoming Jigsaw products. 


Equivalent to ZX81 or TS1000 16K RAM. Fully compati¬ 
ble in appearance and performance with other Jigsaw 
products. 


CALL OR WRITE FOR FREE CATALOG 


Call (716) 874-5510 
For Visa, MC Orders 


Mail order to 1585 Kenmore Ave. Buffalo N.Y. 14217 Checks or money orders. No CODs. Add shipping 

































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MATH FUNCTION EXECUTION TIME 

Some calculations take longer 
than others on my ZX81. I timed 
each math function to get an idea 
of which function to use when faced 
with alternative methods of doing 
the same calculation and to compare 
the ZX81 with other computers. 

Enter in FAST mode: 

1 FOR 1=1 TO 1000 

2 LET T=1 

3 NEXT I 

This program ran in 6.1 seconds 
against a stopwatch. This is the 
basic time to execute a FOR-NEXT 
loop and assignment 1000 times. 

I replaced the "1" in line 2 
with each function in turn and 
retimed the program. Deducting the 
basic loop time gives the time to 
do each function 1000 times. I 
calculated the time in milliseconds 
to perform each function once. 

Execution times vary widely, 
from 4/10000th second to one tenth 
second. This means some methods of 


calculation are better than others. 
For integer powers up to 50 it is 
faster to multiply out than use the 
** function. It takes more memory 
to multiply to get X**50, so there 
is a trade off. Also it's faster 
to use X*0.5 than X/2. 

I tried using the loop variable 
I in the calculations but it didn't 
seem to affect the speed. This 
leads me to assume that the times 
in the table are valid for any num¬ 
bers used with the functions. 

By comparison, most pocket cal¬ 
culators and pocket computers take 
about 200 milliseconds per opera¬ 
tion. Typical minicomputers use a 
few microseconds per operation. 

Execution Times in milliseconds— 
Z0X81 Math Functions 


Function 

Time 

Function 

Time 

ABS 1 

0.4 

COS 1 

40.6 

SGN 1 

0.6 

EXP 1 

41.3 

INT 1 

1.1 

ARCTAN 1 

60.9 

1+1 

1.2 

LN 1 

65.0 

1*1 

2.0 

ARCSIN 1 

69.9 

1-1 

2.1 

ARCCOS 1 

72.6 

1/1 

2.9 

TAN 1 

81.9 

RND 

11.9 

1**1 

105.4 

SIN 1 

39.1 

SQR 1 

106.4 


Ron Charlton, Paducah, KY 
SIGNIFICANT FIGURES SUBROUTINE—8K 

In scientific calculations the 
accuracy of a computed value must 
not exceed that of the least accur¬ 
ately known number used in the 
computation. You can use the fol¬ 
lowing subroutine (at 1000 in this 
program) in any program containing 
the proper input, i.e., SF and Z, 
to specify the number of signifi¬ 
cant figures in any expression. 

Because the ZX81 holds 10**1, 
10**2, etc., slightly inaccurately 
(see part 2 of Dr. O'Hara's 
article, Apr.82), using QE=10**I 
might give erroneous results. For 
example, if SF=6 and 
Z=0.000098765432, using QE=10**10 
would produce 0.000098765399. In 


16 




subroutine 1180, lEl through 1E13, 
which are held exactly, are substi¬ 
tuted for 10**1 through 10**13. 

For Z=0.000098765432 and SF=6, this 
gives the correct value, 
0.0000987654, with the desired num¬ 
ber of significant figures. (Note 
that the ZX81 will not print the 
last significant figure if it is a 
zero to the right of the decimal 
point. It will, however, be 
counted as a significant figure 
by the subroutine.) 

Use this subroutine as often as 
necessary by repeating the GOSUB 
command after assigning each new 
value to Z. The ZX81 can handle up 
to eight significant figures. 

N. Handshaw Clark, Bryan, TX 


10 REH "RNY PROGRRH" 

20 PRINT "HOW MRNY 5IGNIF1CRNT 
FIGURES DO YOU WISH?" 

30 INPUT SF 
4.0 CLS 

"^INPUT NUMBER:" 

60 INPUT Z 
70 CLS 

S0 GOSUB 1000 
90 PRINT 2 
100 STOP 

nil pEM_^"SIGNlFICfiNT FIGURES" 

X0S@ LET I=SF 
X030 GOSUB 1180 
1040 LET ESF=OE 

lie® Z>=<ESFi THEN GOTO 1 

1060 FOR I=s0 TO 30 
1070 GOSUB 1180 

U = 1NT C (RBS Z4-(@.5^0E) ) 

1090 IF W< (ESF^.'lEl) THEN NEXT T 

lifi " 

lia© FOR 1=0 TO 30 
1130 GOSUB 1180 

3^0E? W = INT ((BBS Z.|-(0.S«OE) ) 

>>>= tESF) THEN NEXT 1 

lilt hiruiS 

1180 LET ©E=1©»»I 
1190 IF 1=1 THEN LET OE=lEl 
120© IF 1=2 THEN LET OE=lE2 

1=9 THEN LET OE=lE3 

1220 IF 1=4 THEN LET OE=lE4 

1230 IF 1=5 THEN LET OE=lE5 

lg’40 IF 1=6 THEN LET OE = lE6 

1-26© IF 1=7 THEN LET OE = lE7 

1260 IF 1=8 THEN LET OE=lE8 
"^HEN let OE = lEi 
1280 IF 1=10 THEN LET OE=1E10 

III® 1=11 then let oe=ieii 

13®® 1=12 THEN LET OE=lEia 

iiil RETu5n= OC.1E13 

SYNTRCTIC SUM: 6©191^ 8K 


SYNTAX ERRORS: In Jason Harper's 
Printing on the Bottom Line (Aug. 
82), line 60 of the second program 
should read: 60 POKE 16418,2 

John Oliger of Indianapolis 
wrote of the battery back-up proj¬ 
ect Aug.82: "Mr. Nachbaur refers to 
part nos. LM340T-5 and 78L05 for 
the regulator in this circuit. A 
78L05 would never work. He should 
have said a 7805. A 78L05 (in a 
TO-92 or TO-39 package) is only 
good for lOOma max. The 7805 is a 
1 amp regulator and the LM340T-05 
is a 1.5 amp regulator. Both are 
in the TO-220 package." 

Fred Nachbaur wrote that in 
Fig.2, same article, the arrow 
identifying the emitter lead of Q1 
should be in the top "leg," point¬ 
ing toward the transistor base sym¬ 
bol. Also, Syncware cut R1 to 62 
Ohms, reducing battery warmup after 
extended use by decreasing battery 
charging current. It increases re¬ 
charge time to about 24 hours—no 
problem if the unit is just a back¬ 
up. Higher values (75 or 81 Ohms) 
work but increase recharge times. 

PROGRAM IMPROVEMENTS/REFINEMENTS 

To polish Harold Miller's MC screen 
fill program (Aug.82), change JPNZ 
at 16522 and 16526 to JRNZs. Since 
JRNZs are 2 bytes long, the line is 
just 14 bytes. The same line can 
fill the screen with different 
characters from different places 
in a program without changing the 
JPNZ addresses. The basic line 
reads in hex: 

3E 80 06 04 OE BO D7 

OD 20 FC 05 20 F7 C9 
USR 16514 blackens the screen. If 
you put 3E 88 18 02 in front of 
this line, USR 16514 gives a gray 
screen; USR 16518 a black one. Add 
any number of 4-byte changes to the 
front of the line. Increase the 
code of the 4th byte by 4 for each 
set and increment USR calls by 4 
for each new character fill. 


17 


Robert A. Foley, Umatilla, FL 




The Sinclair ZX81 personal computer kit 


AD CODE 
09SX0K 


Imagine building your own computer 
for only $79.95! 

That’s exactly what you can do with 
the ZX81 kit. It comes with all the parts 
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and a screwdriver. Plus, of course, a little 
bit of work. 

But you get a lot more than several 
hours of kit-building fun. You also get a 
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The ZX81 hooks up to any TV for a 32- 
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the connecting cables). You can also use a 
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programs (again, we provide the cables). 

Most important, you get a BASIC pro¬ 
gramming language that’s powerful 
enough to challenge and interest the 
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ZX81 can handle multidimensional string 
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command. Syntax error detection, de¬ 
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features that are ideal for creating games, 
such as 20 graphic symbols, continuous 


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The ZX81 can be expanded too. You 
can increase the memory from IK to 16K 
with our Memory Module for $49.95. 

And you get a comprehensive manual 
that completely documents the capabili¬ 
ties of the ZX81, and teaches program¬ 
ming from the ground up. 

In short, you get all the features that 
have made the Sinclair ZX81 the fastest 
selling personal computer in the world. 
And you get the satisfaction and fun of 
building it yourself. 

A few years ago, this kind of computer 
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But the ZX81 kit can be yours for only 
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Ask for operator #509. Phones open 
24 hours a day, 7 days a week. Have your 


MasterCard or VISA ready. 

These numbers are for orders only. If 
you just want information, please write: 
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MAIL TO: Sinclair Research Ltd., 1 

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PRICE* QTY. AMOUNT 


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16K Memory 
Module 

Shipping and 
Handling 

*U.S. dollars 


TOTAL 


Sinclair technology is also available in Timex/Sinclair 
computers under a license from Sinclair Research Ltd. 


Name 

Address 


inczlaii— 







MACHINE CODE PROGRAMMING— 

#9: TESTING BITS FOR BRANCHING 

You can test any bit in any 
address simply by loading a regis¬ 
ter and choosing the right instruc¬ 
tion code. This facility is fairly 
easy to understand and can be used 
even in very short machine code 
(MC) subroutines. 

For example, if you have a 
block of data with both positive 
and negative values less than 128, 
you can use the instruction BIT 7,A 
after loading A with a value. If A 
is positive, the Z Flag will be set 
to 1; if A is negative, the Z flag 
will be reset to 0. Then a Test- 
and-Branch (T&B) can give the value 
to the correct area for processing. 

How does this instruction work? 
The 7th bit in A, either 0 or 1, 

"+" or is "inverted" and put 

into the Z bit of the Flags regis¬ 
ter. If your T&B is JR Z and the 
7th bit of A is 0, then Z will be 0 
and control will not jump. Remem¬ 
ber that a Flag is "true" if equal 
to 1, or "set". 

Another example: suppose you 
have a block of data with odd and 
even values less than 256, and 
you want the addresses of the odd 
values. One solution is to set up 
a loop with HL. (Odd values will 
have a 1 in bit 0; even values will 
have a 0 in bit 0.) 

The possibilities are endless, 
so here are some general rules: 

1. Select the proper instruction. 
If the address is important, use 
BIT n,{HL). If the value is 
important, use BIT n,register. 

2. First, load the proper register 
(or HL pair) with the value (or 
address), then test the bit. 

3. Follow the bit test with a 
Test-and-Branch instruction with 
two possibilities: 

A; Bit test fails—continue 
search loop (Ex. JR Z ;Z=0) 

B: Bit test succeeds—Branch 

to processing area (Z=l) (or. A: 

JR NZ for branch and B: Continue 
search loop.) 


4. If your data block is used more 
than once per USR-call, then add a 
"trigger" value into the last data 
address for a "value" Test-and- 
Branch to an area for resetting the 
address-pointer. 

Next month: JUMPING AROUND 

Jon Bobst, Zeta Software, PO Box 
3522, Greenville, SC 29608-3522 

HARDWARE REVIEW 

Product: ZX99 Tape Control 

System 

From: Data-assette, 52 S. 3rd 

St., Oxford, PA 19363, 
215/932-3626. 

Price: $150 (includes cables) 

Don't be fooled by the name. 
This is a tape operating system. 

And a good one. 

Data-assette's ZX99 Automatic 
Tape Control System can read and 
write records (called blocks) that 
let you keep data files separate 
from programs. You can read in two 
program tapes, concatenate them and 
write out a new program tape. You 
can generate blocks containing only 
single values or read a 4K tape 
into a string and write a program 
to automatically translate it to 
8K. In short, you can have most 
disc functions at low cost. 

The hardware is well built; 
the manual is not. It took me some 
time to understand that I had to 
operate the recorders manually in 
the LOAD and SAVE modes. Selecting 
recorders turns them on before you 
can type the LOAD or SAVE commands, 
unless you stop them by hand before 
selection. This mode bypasses ZX99 
control and puts you in the normal 
TS computer mode. 

Unless your programs RUN auto¬ 
matically and reset the ZX99, your 
control program can't LOAD and then 
stop the recorder—LOADing wipes 
the control program. 

When using the ZX99, you can't 
use other boards using addresses 


19 


8192-16383. You must configure 
Memotech 64K to select neither the 
8-12K nor the 12-16K block; nor can 
you use printer interfaces with 
these adresses. This flaw results 
from incomplete decoding of the 
ZX99's 2K ROM addresses. 

ZX80 owners must work out how 
to add ROM CS to pin 23B of their 
machines to use a ZX99. 

We tested most ZX99 functions 
and found them reliable. We ran 
into some problems caused by (we 
think) a loose connection. Check 
the setup carefully: problems show 
up as oscillations on the recorded 
tapes, making them unuseable. 

Additional memory setups tried 
created high-frequency noise in the 
quiet spot on the tape. Sinclair's 
16K RAM couldn't write a tape that 
reloaded—the hash was too loud. 

Our Memotech 64K and TS1016 made 
noisy but usable tapes. Our IK 
machine produced quiet tapes. 

Cables supplied with the sys¬ 
tem connect the recorders and your 
computer cables connect the ZX99. 
You must make your own printer 
cable to connect a 3.5mm plug and a 
connector to match your printer. 

Listing to a serial printer 
via the RS232 port is very simple. 
Define a value (Y) that programs 
the interface, then call USR 8225 
to start the listing. Lines will 
be your printer's maximum width or 
60 columns, whatever comes first. 
Lines ending in keywords extend 
past the margin to complete the 
keyword, but not its argument. You 
can't create a screen format in the 
LIST mode. Extra blank lines follow 
GOTO, STOP or RETURN as an aid. 

In BLOCK PRINT mode, a shifted 
T prints the TS "<>" character 
which generates a carriage return 
and line feed for your printer. 

In either mode you get full 
128 character ASCII output. You 
can't send from a terminal to the 
computer. Baud rates from 110 to 
9600 are available under software 
control. Handshaking isn't avail¬ 
able, but you can choose even or 


odd parity generation. A simple 
choice in software exchanges the 
relation of caps and lower case to 
normal and inverse video. 

On our printer (a CDI 1205 
terminal) print lines were right- 
justified in the buffer if "<>" 
used for CR/LF was at the end of 
the line. Under these circum¬ 
stances the right margin wandered 
about three characters. When LF/CR 
is at the start of the print line 
we get left-justified text and 
stable margins. The 47-page manual 
failed to explain this and it took 
several hours to learn. 

Data-assette told us a minor 
ROM bug was found and all early 
buyers got free upgrades. 

Despite its limitations, this 
is a powerful add-on to your ZX/TS. 
Syntax has seen no other program 
development aids that allow this 
level of flexibilty.—KO 

CLASSIFIED ADS 


Reach thousands of ZX80/81 owners! 
Send your ad, typed 35 char/line, 
with check to arrive by the 15th of 
any month for the next month's 
issue. Ads arriving after the 15th 
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Ads are $9 per line and must be 
resubmitted for each month. No 
phone orders or credit cards. We 
take no responsibility for adver¬ 
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Exc display by team,division,&more! 
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Hurry!The season is about to begin! 
16K,ZX81 Tape $9.95 Money Orders 
sent same day. ZAMIS ENGINEERING 
251 First St., Perrysburg, OH 43551 

SYNTAX offers a faster way to find 
answers! NEW Laminated Micro¬ 
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Z80,6502, 8080A & 8085A, 8048 & 
relatives, and programmers' 


20 




algorithms ref. card, $5.95 each. 
Prices include shipping. SYNTAX RD 
2 Box 457, Harvard, MA 01451. 

**********THE FUNWARE CO.********** 
l.LAND THE SPACE SHUTTLE 2.LAND/AIR 
BATTLE 3.SPACE BATTLE 4.HUNTMAN*ALL 
ZX-81/16KRAM ON QUALITY C-20 TAPES, 
each game $4.95 or all four $16.95. 
PAPER FOR ZX/PRINTER $6.50 PER ROLL 
All prices include shipping/handle. 
7119 Santa Fe Av. Dallas, Tx. 75223 

BRAINWAVES & ZX81 CONTROLS MUSIC 
speech, robots. News & catalog $3. 
Rosetronix 269 Dahlia I.B.CA. 92032 

Software for all Sinclair Computers 
WRITE FOR OUR FREE CATALOG & CODING 
& DISPLAY SHEETS:Lamo-Lem Labs,Code 
115, Box 2382, La Jolla, CA 92038. 

PARENTS/TEACHERS—4 pgms for pre¬ 
schoolers and spec. ed. students. 
Develop beg. reading skills. Large 
letters, rewarding graphics. Cass¬ 
ette for ZX-81,16K. $20ppd. SCREEN- 
MAKERS, 351 Badger, Guffey, CO80820 

<*VOTEM*> Analog Interface* Measure 
voltage & temperature with your ZX* 
$39.95/kit-$59.95/asm-$5/doc alone* 
Add $3/USpost* Down East Computers* 
PO Box 3096A, Greenville,NC 27834 * 

Finally, a GRAPHICS DUNGEON FAN¬ 
TASY GAME . Treasure Seeker . find 
booty & fight monsters. Plus: MARS 
LANDER, SKIIER, CRUMBLIN CAVERNS. 
All on tape for $6.95. Send money 
tozSpartan Software, 1403 Gloria, 
Boulder City, NV 89005 (8K/16K) 

On cassette; 3 new game programs 
for the 16K ZX81; $6.00;OCH Jr. 

RT. 3, BOX 229, AMITE LA70422 

DRY GULCH. An interactive adventure 
written in the classic style. Over 
100 words of vocabulary. This one 
will take days to solve. Written 
in BASIC, it is listable and may be 
SAVEd in progress. 8K/16K. Send 
$10 for a cassette to; UPSTATE LABS 
27 ELVIRA STREET ROCHESTER,NY 14606 


EVEN BETTER THAN BEFORE! 

TH£ SINCLAIR COMPUTER FAMILY SOURCE 
BOOK (1st Revision) lists over 600 
programs, books, & accessories from 
over 80 suppliers. Only $6.95+$1.25 
P&H. VA res. add 4%. Send check or 
Money order to ATLANTIC COMPUTER 
PRODUCTS, POB 936 Norfolk, VA 23501 
*********************************** 

"COIN COLLECTION" Menu format; 
add/delete,check inventory,change 
cost/value,total cost/value,search, 
auto-run/auto-save & morelListable. 
8K ROM,16K RAM. Tape+manual $10.95 
"UNIVERSAL INVENTORY FILE" You 
create the file headings. Menu and 
prompts. Two ways to search, add/ 
delete,check&more! 8K ROM, 16K RAM. 
Tape+manual $16.95. M.C.Hoffman Co. 
P.O. Box 117, Oakland, N.J. 07436 

UTILITIES FOR SERIOUS PROGRAMMERS 
—R/W(8K/2K) Data tape read/write 
(can also read SAVEd tapes as data) 
—MRG(8K/16K to be useful) BASIC 
save/merge/erase (combine in-RAM + 
taped BASIC). Self-load ML cass - 
ZX81/TS1000. R/W only $10; both for 
$15. SASE for info. SIRIUSWARE 
6 Turning Mill Lexington MA 02173 

POWERSUPPLY REPLACEMENT WALL PLUGIN 
For ZX81 handles lK,16K,32K,and 64K 
RAM. Won't overheat or lose memory 
under continuous or intermittent 
duty.Send check or MO for$19.95 to; 
D&B Power 204 N. Fehr Way Bayshore 
NY 11706 Dept G. Includes P&H 
NY res. ADD sales tax Fast delivery 

PRESCHOOLERS have fun and learn on 
SCREENMAKERS readiness programs. 
Write 351 Badger, Guffey,0080820 

Engineers,contractors-design prog¬ 
rams written by PE; H/AC load,duct, 
plumb.,sprinkler.Free cat-P Symonds 
1345 Dewey Ct., Rockledge, FL 32955 

Kit to solve ZX81 heat dissipation 
problem.INSTALLS IN SECONDS. Send 
3.95 chk/mo to: R.H.,Inc. 7683 
Thompson Rd. Cincinnati, Ohio 45247 


21 



AIRPLANE FLIGHT SIMULATOR.RADIOS(2 
chans): VOR,DME,ADF,Glideslope. Map 
display shows position(movable). 
Multi-leg trip ends with instrument 
landing.Instructions.Cassette for 
ZX81/16K. Send $9.95 check or money 
order to: AMANDA SYSTEMS, 

P.O.Box 118, Holmdel,NJ 07733 

BASE CONVERSION for ZX-81 w/16k. 
Great machine language aid! Tape 
$5.00. Maracomp,1525 N. Euclid 
#122, Tucson,Az. 85719 

>>>>> STUART SOFTWARE PRESENTS <<<< 


> < 

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> < 

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> Football league games-Complete < 

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> Order from; STUART SOFTWARE < 

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> Enclose $1.50 shipping/handling < 


LOADING PROBLEMS? — Our cassette 
interface works! Complete systems, 
29.95; 39.95 w/led indicator. Over 
20 PROGRAMS AVAILABLE! SASE to: 
Phoenix Engineering Systems, 4240 
Lakeshore, Deckerville, Mi. 48427 

"EPHEMERIS V" (c) for the 16K ZX-81 
Merc., Venus, Mars, Jup. & Sat. all 
found w this 16K prog. NO CALCULA¬ 
TIONS. Any date, time and place on 
Earth. Graphic disp. in, and loc of 
current constell. in simple terms. 
PLUS r.a. & dec. & LOCAL side, time 
For this amazing tape send $8 to: 
Ephemeris V, 124 Professional Ave. 
P.O. Box 261, Winchester, KY 40391 

COMPUSETTE is a C-10 cassette which 
is especially designed for micro¬ 
computer application by TAPEMASTERS 
25 for $20.00 100 for $70.00 

VISA MASTERCARD C.O.D. 

TX 214-349-0081**OTHER 800-527-1227 
10% Discount for Check with Order 
P.O. Box 38651*Dallas, Texas 75238 
FREIGHT PREPAID*DEFEGTIVES REPLACED 


MONKEY BARRELS for IK ZX81! Climb . 
bldg, jump barrels or die! Listing 
$2. PANERO SOFTWARE, 3309 Lewis, 
Long Beach, Ca. 90807. Exciting!! 

FIFTY NIFTY PROGRAMS FOR YOUR ZX81! 
Book has 50 Top Quality IK programs 
w/instructions+comments. Plenty of 
GAMES/GRAPHICS/FUNSTUFF. ONLY $9.95 
LEE CARTER Bx 246 Harrison,ME 04040 

RAMPAK OWNERS. DECODER fits inside 
ZX80/81 and remaps internal ram to 
8-9(10)K. $5.95pp-USA. JOHNOLIGER 
10115 Nassau Ln. Indpls. In. 46229 

m LISTABLE PROGRAMS ON 1 CASSETTE" 
Mastermind,Doublemind,Slot Machine, 
Craps,TicTacToe,Sub Rescue,WhiteHot 
Number.NEW ENGLAND SOFTWARE,Box 691 
Hyannis,MA 02601.lK-$7.95,16K-$9.95 

** SALE -ZX81 CONNECTOR $4.85,5/$23 
2K RAM$12,0-16 PORTl/0 w/KEYBOARD 
PLANS $5,ADD 50t PER CONNECTOR P&H 
POWERTRONIX 25E23 Bayonne, NJ 07002 

CREATE OUR OWN GAMES-10 IK programs 
reveal moving graphics techniques- 
tanks,D&D,Bombs&more-Listings$2 
Q&M Pub.225N.1600W.#76Provo,UT84601 

16K-"ZX81 MONOPOLY"or "TRADER JACK" 
Monopoly in Spanish,Amer or Britain 
Trader Jack in South Pacific 
SAVAGE SOFTWARE- SW IMPORTERS 
PO BOX 441 TITUSVILLE, FL 32780 

ARTIST is a 8K/16K program that, 
with more than 25 commands, helps 
create drawings/paintings on screen 
Features include: user's choice of 
brushes and backgrounds, free mix 
of graphics and alphanumerics, easy 
specification of lines and circles, 
ability to store and recreate com¬ 
plex patterns by defining new 
commands, and to save the artwork 
on tape or print it. $10. KSOFT, 

845 Wellner, Naperville, Ill 60540 

Z-SHIRT says ZX COMPUTER POWER. Top 
quality shirt. Kids (SML) or Adult 
(SMLXL). Specify. $8.50ppd SCREEN- 
MAKERS, 351 Badger, Guffey,CO 80820 


22 



NEW ZX81 heatsink eliminates system 
crashes due to overheating SASE to: 
B Sanzone 289 Baxter La Milford CT 

CENTRONICS SYTLE PRINTER INTERFACE* 
for typing labels,forms,letters,or 
program results. Large or small 
letters or Graphics using GP-100A 
printer. Board $45, cable $22.50. 
Professional Electronics,109 Ches 
ney Lane,Columbia,S.C. 29209 _ 

OUR POLICY ON CONTRIBUTED MATERIAL 

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

We welcome program listings for all levels of expertise and written in either 
Sinclair BASIC or Z80 machine code. 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. Programs submitted on cassette can be 
tested more quickly and with less chance of error. 

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 (program published in Feb. 81 and Jun. 81; send SASE 
for a free copy). 

• What RAM size program requires. 

• What ROM program uses. 

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, stamp>ed envelope. Otherwise, we cannot return submitted material. 


PII2 THAT SINCLAIR TQ WORK ! 1 
ZX Phone Book 16K. Holds 720 fully 
editable names! Very useful index/ 
cataloging tool. List/notes...$4.95 
Tom Woods Box 64 Jefferson,NH 03583 

SPECIAL3PROGRAMSZX81SEND$H-SASE 
to PO Box 3073 San Jose,CA 95156 

AMATEUR RADIO LISTS 16K DXCC & QSL 
Manager Both $4.95 Pierce Co. Box 
131 Derby KS 67037 

CURVE FIT PGMS/ZX81 IK $10.00/John 
Anunti,3309 20th,San Fran.,CA94110 

12" B&W video monitor only $89.95. 
Includes plans and kit for direct 
video modificatin of ZX81.Random 
Access box 41770S Phoenix,AZ 85080 

BUFFERED BUSS/DEVELOPMENT BOARD for 
ZX80/81: $40=BARE BOARD, $65=KIT. 
UHF modulator $15. Connectors $6. 
ZX81 REPAIRS $20+parts. Send for 
details.COMPUTER CONTINUUM 301-16AV 
San Francisco,CA.94118.(415)5243730 

ZX81 ASSEMBLER & ZX81 DISASSEMBLER 
on cassette $15. for info,send SASE 
SERIAL PRINTER interface (thru MIC 
port) plans & listing $5. Bob 

Berch 19 Jaques Rochester NY 14620 


SYNTAX 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 


© Syntax ZX80, Inc., 1982. 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___ 


exD. date 

bank number fMC onlv) 

signature 

Name 

Title 


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Dav Phone ( 

) 

Evening Phone ( ) 



9 8? 

I own a □ Sinclair ZX80 

□ Sinclair ZX81 Telephone orders call 


617-456-3661 


23 




EZRA GROUP II 
EZRA GROUP II 

LOW LOW LOW LOW LOW LOW LOW LOW LOW 


PRICES! 

Biorhythms 8K ROM/lK&up.1.00 

Graphics billboard 8/lup.1.00 

Horse Race 8/lup.2.00 

SPINNER TM(like Rubik's)8/16...2.00 

Improved SLOW PAUSE.1.00 

Linear Regression 8/lup.2.00 

CHAR. Generator Demos 8/lup....2.95 
TAP WRITER TM(Handicap Aid)8/1.free 

SPLIT-A-STACK TM SLOW/lup.2.00 

CHEWTER TM(like PACMN)SLOW/lup.2.95 

ISLAND SQUARES TM SLOW/2up.2.00 

Random MUSIC!SLOW/lUP.2.00 


BASIC keyword Demos 8/1....from .50 
ORDER,SASE,reSASE gets you GOO¬ 
DIES Catalog and MFREEI! Program 
EZRA GROUP II 
EZRA GROUP II 

POB 5222 San Diego,California 92105 

**ADD MEMORY THAT WON'T FORGET! ! ** 

* Complete kit; $31:90 incl.s&h * 
Full details w/stamp; HUNTER 1630 

* Forest Hills, Okemos MI 48864 * 

***MECHANICAL DESIGN PROGRAMS*** 
Programs provide tested solutions 
expandable ideas & solutions of 
Machine design problems. Send 
$5.00 for sample programs to, 

M.R. MADIGAN 295 Westview Ave. 
Wadsworth, Ohio 44281 


Tl-E 

H\RV\RD 

GROLP 

Bolton Road. Harvard, Mass. 01451 




Speed it up! Your programming that 
is! Non-Trivial Solutions' ZXPRESS 
IntegerBasicCompilerCompiles ZX- 
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This means your programs can be de¬ 
bugged rapidly in Zx-81 BASIC, then 
stored in REM statements or in 
2000H to 3FFFH address segment, if 
available. The ZXPRESS Compiler 
will make your ZX-81 20 to 50 times 
faster. It's variables are 16 bit 
two's complement integers. The com 
piler allows multiple statements/ 
line. With the ZXPRESS the source 
code can be located anywhere and 
the position of the compiled code 
write a long program, compile it in 
pieces, then assemble the pieces. 
The ZXPRESS is available from N-TS 
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to offer the games Letter Raiders 
and Life with Palette for $9.95 
each. NON-TRIVIAL SOLUTIONS, P.O. 
Box 2941, Amarillo, TX 79105, 806/ 

376-5723. Check, MC, Visa welcome. 
*********************************** 

*********************************** 

♦CUSTOM ATTACHE CASE Formfit for * 
*ZX80/81,TS 1000 and hardware for * 
♦info send SASE COMPUTA-DEK 6009 ♦ 

♦Kenwood Dr. Nashville, Tn. 37215 ♦ 
*********************************** 


U.S. Postage 

First Class Harvard, MA 

Permit No. 8 
01451