SYNTAX ZX8U
A PUBLICATION OF THE HARVARD GROUP
VOL. 3 NO.6 ISSN 0273-2696 JUN.,1982
IN THIS ISSUE
SINCLAIR DROPS US ZX PRICES AS OF 1 JUNE
8K Programs
Annuity.17
Line Renumbering.4
Loading Hex Listings.18
Screen Background....20
Book Review
ZX81 Programming for
Real Applications.8
Classified Ads.20
Dear Editor.12
Expanding 16K Programs.15
Hardware Preview
RD8100 & Modules.16
Hardware Project
Adding a Joystick
to ZX80/81.10
Numbers Held Inexactly.19
Machine Language
Exchanging Registers..9
News, New Products .... 1,2
Package from England....6
Program Corrections
and Improvements.2
Report from 3rd
ZX Microfair.11
Software Review
Adventure A.17
Users' Groups.13
Index of Advertisers
Bani-Tech.15
CAI Instruments.7
Kopak Creations.9
Lamo-Lem Labs.14
LJH Enterprises.10
Memotech Corp.3
S&S Co.18
Softsync, Inc.8
Zeta Software.5
SYNTAX Subscription
Information.23
Sinclair Research lowers the prices
on their ZX products in the US 1 June 1982,
according to Margaret Bruzelius of Sinclair.
New prices: Assembled ZX81, $99.95; ZX81
kit, $79.95; 16K RAM pack, $49.95.
ZX81 owners will receive a new software
brochure this month. ZX80 owners should
write to receive a copy.
SPECTRUM SHOWN AT LONDON ZX FAIR
SYNTAX editors saw Sinclair's Spectrum
at the 3rd ZX Microfair in London (see May
82). Don't bother writing to friends in
England to get one early—Nigel Searle of
Sinclair says that the Spectrum now works
only with British 50 Hz TVs. But he also
suggested that the Spectrum's•Dec.82 arrival
announced in SYNTAX may well be earlier.
NEW PRICES FROM CAI
CAI Instruments of Midland, MI,
announced new prices for their ZX peripher¬
als. The thermal printer is now $119.95.
The CAI/O board, formerly the Widget, is
$79.95 alone and $69.95 with any other CAI
device. The tape drive system is $99.95.
Bob Swann of CAI says all products are now
available for 30-day delivery. CAI also
offers a free software catalog. CAI Instru¬
ments, 2559 Arbutus Ct., Midland, MI 48640,
517/835-6145.
BYTE-BACK MODEM SHIPMENTS DELAYED
Byte-Back of Leesville, SC, will ship no
modems for 4-6 weeks, according to Helen
Minchey of Byte-Back. They are shipping
memories. The modem is $99.95 and includes
RS-232 port and software. Byte-Back, Rt.3
Box 147, Brodie Rd., Leesville, SC 29070,
803/532-5812.
1
SYNTAX ERRORS: Using Program 1 in
Frank O’Hara's Numbers Held
Inexactly, Apr.82, 1E13 gives 172
17 132 231 42.
PROGRAM IMPROVEMENTS
Marty Irons of Goshen, NY,
sent this version of Herb Magnus'
READ-DATA-RESTORE (Apr.82). It
loads an array from a literal
string, including decimal places
and multipliers. Line 30 sets the
decimal point. Use P=0 for inte¬
gers, P=2 for two decimal places.
P=-3 multiplies the value by 10 .
Line 10 sets the numbers of entries
in array D. Line 40 sets the char¬
acters/number. Line 50 holds data.
Line 75 prints results. If A$ is
too short for the READ routine (60-
80), error code 3 results.
10 LET E = 10
£© DIM D (E'f
30 LET P = £
4-0 LET L = 3
50 LET R$=“ 1234567890123455789
01234.587890**
60 FOR 1 TO E
70 LET D (N) = CURL ifiS CH*L~L + i T
O N *L) 1© >
75 PRINT “E N; **)**, “ =
80 NEXT N
syntactic sum: 9309, sk
Frank O'Hara of Surrey, UK
sent a 16K version of Bill Wentz'
Flower Plot (Apr.82). Load points
into an array in FAST, then go to
SLOW for a moving display, which
repeats after a flicker-free pause.
This method works for all such dis¬
plays. For N=99 and 999, try 301
for 601 in line 78.
5 REM HOTHOUSE PLOT (16K)
6 FRST
7 DIM X(601)
8 DIM Y (6SI)
IS LET N=4-56
20 LET D=2iPI/6S3
38 LET P-20
4-© FOR I=© TO 500
5© LET T=D*I
55 LET R=PS5IM (N*TJ
6© LET X(1+1)=R*COS T+31
-7© LET Y(I + 1) =R)tSIN T +21
73 NEXT I
74. SLOU
76 CLS
78 FOR 1=1 TO 60-1
S© PLOT XCI) .Yd)
9© NEXT I
1@0 FOR 1=1 TO 1©0
IX© NEXT I
120 GOTO 76
SYNTACTIC SUM: 19308 .. 8K
Bill Bruton cf N.Olmstead, OH,
sent these changes to Lane Lester's
Income Tax program (Mar.82 p.8):
The first 3 characters from
line 2124 don't clear before line
6000 executes. Change 6000 to
PRINT AT 21,0...Change 9006 to REM
DIM C$(107,18) to remind you of the
direct command to enter during
initialization. The 18-character
line description will only be 1
character without it.
Line 2220 simply sums the
previous 4 lines—a problem for
casualty or theft losses. To fix
the problem and save entries:
£219 LET L(93) =L(91) -L(94-)
£220 IF L(93) <© THEN LET L(93)=0
£221 LET LC94)=LC93)
2222 IF L(94T>i0© THEN LET L(94>
= 188
2223 LET l taoJ =L (93) —L (94-)
2224 LET L(98)=L(S6)^L(97)
2225 LET L(99) =L (76)
A refinement for rounding:
2200 LET L(69)=INT (Lt31J+.5)/i®
©
22©1 LET L (78) =L (63) — L (39)
2206 LET L(74)=3*L£69>
Line 2160 can cause a problem
when reviewing data because of
computer precision shortcomings.
Part of the display will be over¬
written by the message at review
end because of lines over 32 char¬
acters. Change line 2160 to:
2160 LET L(63)=INT (100*X+.5)/10
0 *
NEW PRODUCT ANNOUNCEMENTS
ZX FORTH, a FORTH derivative for
16K ZX81s, is available from SofTek
Company, Santa Fe, NM. Package
costs $20+$2 postage and includes
examples of a fully documented
source listing. Contact SofTek,
Box 4232, Santa Fe, NM 87502-4232.
Battery back-up units are available
from Syncware. BBU-2 ($84.50) runs
a ZX81 with 16K RAM for over 2
hours, BBU-1 ($54.50) 1 hour, and
Baby BBU ($39.50) up to 15 minutes.
Prices include shipping. All three
models include LED indicators and
on/off switch. BBU-8, running up
to 8 hours, will be available early
Jul.82. Syncware Co., 4825 Elrovia
Ave., El Monte, CA 91732.
2
Explore the excellence of your ZX81 with a
ramOPRIi 64k memory
Give your diminishing
extension for
memory more
$179.95
byte.
MEMOPAK 64K RAM $179.95
The Sinclair ZX81 has revolutionized
home computing. The MEMOPAK 64K
RAM extends the memory of ZX81 by a
further 56K to a full 64K. It is neither
switched nor paged and is Directly
Addressable. The unit is user trans¬
parent and accepts such basic com¬
mands as 10 DIM A (9000). It plugs
directly into the back of ZX81 and does
not inhibit the use of the printer or other
add-on units. There is no need for an
additional power supply or leads.
Description of memory
0-8K . . . Sinclair 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 64K extension the ZX81
is transformed into a powerful com¬
puter, suitable for business, leisure and
educational use, at a fraction of the cost
of comparable systems.
ninontn
Memory Extention Specialists
Memotech Corporation
7550 West Yale Ave., Suite 200
Denver, Colorado 80227
Ph.(303) 986-1516
MEMOPAK 16K RAM $79.95
With the addition of MEMOPAK 16K,
your ZX81 will have a full 16K of Di¬
rectly Addressable RAM. It is neither
switched nor paged and enables you to
execute longer and more sophisticated
programs and to hold an extended data
base.
The 16K and 64K Memopaks come in
attractive, custom-designed and engi¬
neered cases which fit snugly on to the
back of the ZX81 giving a firm connec¬
tion.
Free service on your MEMOPAK
Within the first six months, should any¬
thing go wrong with your MEMOPAK,
return it to us and we will repair 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.
Coming soon.
A complete range of ZX81 plug-in
peripherals: •
MEMOTECH Hi-Res Graphics
MEMOTECH Digitising Tablets
RS232 Interface
Centronic Interface and
Software Drivers
All these products are designed to fit
“piggy-back” fashion on to each other
and use the ZX81 power supply.
Further information forthcoming.
I~Mp
>§■
Memotech Corp. 7550 W. Yale Ave. Suite 220 Denver, Colo. 80227
Yes! I would like to try the Memopak. I understand that if I’m not complete satisfied,
I can return it in 10 days for a full refund. Price + Qty. Amount
Act. No.
Name
Street
City_
□ Check
Memopak
64k RAM
$ 179.95
□ Visa
Memopak
16k RAM
$ 79.95
□ MC
Shipping
and Handling
S 4.95
$ 4.95
Total
Exp.
t U.S. Dollars
State
Zip__
STX06
LINE RENUMBERING—8K/16K
Here are two approaches to
line renumbering, one in BASIC and
one in machine code. Neither of
them renumbers GOTOs or GOSUBs.
Whenever you write a program, load
your choice first, then execute it
after entering your program to
clean up line numbers.
BASIC
This program works on an 8K
ZX80 or a ZX81 with 16K RAM. Load
the renumbering program (RENO),
then write your program. Execute
RENO by entering RUN 9965. After
renumbering, I save the program
with RENO attached in case I want
to modify and renumber the program
later. RENO begins with a STOP
statement to separate it from the
program being written, and resides
at the end of allowable line
numbers. To try it out, enter a
few statements with random line
numbers and then RUN 9965 to
renumber them as you wish.
Larry Lockwood, Yorba Linda, CA
936 4
9965
RING
9966
9967
9966
9969
6 *PEEK
RT 8, Ij "STfiRT RENUMBE
STRRT
STOP
PRINT
RT?
INPUT STRRT
PRINT RT 3,21; “ *'
LET RDDR=16589
LET LINE=256iPEEK
EK (RDDR+13
9970 IF LINE=STRRT
8
9971 IF LINE-9964- THEN GOTO 9975
997a LET LENGTH =PEEK (RDDR+21 +25
(fiDDR+3) ~
(RDDR)+PE
THEN GOTO 997
j<3"73 i f=-r
9974-
9975
RESS
9976
9977
9978
RDDR-RDDR +4- +L ENGTH
GOTO 9969
STORTING RDD
1; *' RENUMBER BEG
10,24-; " ; NEU; M
13,1;”INCREMENT
LX
PRINT RT 8.1;
NOT FOUND»“
PAUSE 280
GOTO 9965
PRINT RT 10
INNING UITH?”
9979 INPUT NEU
9980 PRINT RT
9981 PRINT RT
NES BY?"
9982 INPUT INC
9983 PRINT RT 12,19;" " ; INC; ** . "
9384- PAUSE 15©
9985 CLS
9988 IF PEEK (RDDR) =38 AND PEEK
C RDDR + 11 =236 THEN GOTO 9996
9987 IF NEU > =9984- THEM GOTO 9998
9988 LET MSB=INT (NEU/256)
9989 LET LSB=MEU~256fHSB
999© POKE RDDR,MSB
9991 POKE RDDR+i,LSB
9992 LET LENGTH=PE£K (RDDR+2)+25
©*PEEK (RDDR+3}
9993 LET RDDR=fiDDR+4+LENSTH
9994- LET NEU=NEU + INC
9995 GOTO 9986
3996 PRINT RT 10,5;“RENUMBERING
COMPLETED"
9997 STOP
9998 PRINT RT 16,5;“CfiNNOT COMPL
EXE . "
3399 PRINT RT 12.6;“LINE NO. >99
64 . . **
SYNTRCTIC SUM: 5654-3 , 3K
Machine Code
This program renumbers program
lines at any time. It is stored in
machine code and safely tucked away
behind a new RAMTOP of 32000. It
sets the first line to 10 and
increments the rest by 10s. No
STOP statement is needed to signal
the end.
Enter the program as shown,
then RUN. Enter the numbers in the
table (33,125, etc.). This is the
decimal listing for the machine
language the Z80 CPU understands.
Now delete lines 20-70 and
150. Note the REM 1234... line is
different.
Save the program by entering
GOTO 200. It runs automatically
when LOADed. You will see a
flicker and the K cursor on the
screen. To test it, type in a
short program with random line
numbers. To renumber, enter RAND
USR 32000.
To start with a line number
other than 10, POKE 16518,X (where
X=line number you want). If you
want to increment the lines by a
number other than 10, POKE 16534,Y
(where Y=number to increment by).
Mike V. Mullen, Lawrence, KS
X©
REM 1234-56789©!
234567596123
4-567
2©
FOR X = 16514- TO
1654-0
30
SCROLL
4-0
INPUT I
5©
POKE X,I
6©
PRINT X,PEEK X
7©
NEXT X
S©
LET L ss 165 14.
90
FOR X = 32®©0 TO
32®26
100
POKE X,PEEK L
XX©
LET L=L+1
4
123
NEXT
X
13©
POKE
15388 ©
14-3
POKE
1S3S3,125
15©
STOP
IS©
NEU
20©
5RUE
“ REMUM ”
213
RUN
DECIMAL LISTING
33
125
64 17
10 0 114
35
115
35 78
35 70 35
9
126 214 118 200 1 10
0
235
9 235
24 235
ASSEMBLY LISTING
Dec
Hex
OpCode
Comment
33
21
LD HL,NN
loads 16509
125
7D
into HL
64
40
17
11
LD DE,NN
loads 10 into
DE as 1st line
number
10
0A
0
00
114
72
LD (HL),D
insert new line
number
35
23
INC HL
115
73
LD (HL), E
35
23
INC HL
78
4E
LD C,(HL)
^Loads length of
line text into
35
23
INC HL
BC (B is high
70
46
LD B,(HL)
byte)
35
23
INC HL
9
09
ADD HL,BC
sets HL pointer
126
7E
LD A,(HL)
to next line of
text
214
D6
SUB A,N
check for code
118 (indicates
end of program)
118
76
200
C8
RET Z
return to BASIC
if at end
1
01
LD BC,NN
increment line
number by 10
10
0A
0
00
235
EB
EX DE,HL
9
09
ADD HL, BC
235
EB
EX DE,HL
24
18
JR, DIS
jump to con¬
235
EB
EX DE,HL
tinue renum-
bering (is
shown in 2's
complement)
ZX81 OWNERS with 16K RAMI
IT'S READY- —ARE YOU?
$14.95 +
2.50 S&H
If so. .you get:
*24-row/ful 1-screen displays
^Nearly 2K of machine code
for FAST real-time graphics
*A 4K Star Atlas as the moving
backdrop during enemy engagements
*9-each fuel and skill levels that
are interlocked for more "reality"
*4 ways to lose—no fuel, no oxygen,
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"
*"B1 ink"-less pauses in BASIC
*Stick-on/peel-off custom keys
*In-depth booklet explaining both
the "game" and the program
^Shipped on a certified cassette
1 copy each side
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,
.L . Statistics, and RPN Calculator
”7 .*E.S.P.-test your precognition
ETA *Many others plus 6 IK 6-paks
ct'i a i a DC ’ including Machine Code
pFTWARE^r WRnE for free catalog< (In
T Europe, send U$1 bill or DM2 stamp:
DELTASOFT/Osterfeldstr.79D/D-2000 Hamburg 54 GER)
fTlail coupon or copy with payment to:
o | ZETA Software/PO Box 3522/Greenvi1le,SC 29608
CO I
CTi
00 I Enclosed is $_ DCheck □---
b? | for _ copy(ies) of SCOUT FIGHTER ZX81 16K
- plus $2.50 S&H for the order.
r\ i 0\ I '
I ADDRESS_
1 CITY/STATE/ZIP_
I Please allow 4 weeks if paid by check.
5
A PACKAGE FROM ENGLAND
Or, How I got a real ZX printer
If, like me, you cannot wait
for Sinclair or Timex to put a
printer on the US market, you can
order a ZX printer from:
David Finlay, Stationery Mgr.
W.H. Smith & Son Ltd.
124 Holborn
London EC1N 2TD
England
Mr. Finlay informed me that W.H.
Smith would happily accept orders
from the US if. you pay by US trav¬
elers checks made out in British
pounds Sterling (available in
larger banks). The printer costs
£59.95 plus £6 for airmail postage.
Extra paper (you get one roll with
a printer) is £11.95 for 5 rolls.
Do include postage .
In less than a month, it was
here—my ZX printer direct from
England! I sat down eagerly to use
it, but the power supply sent with
the unit was a 230 VAC 50 Hz. What
to do now? I hastily put together
a 115 to 230 auto-transformer and
connected the power supply and
printer according to directions. I
entered a program onto my 16K ZX80,
pressed COPY then NEWLINE (ENTER)
and the printer took off. It
worked beautifully, printing out
the entire screen.
After using the printer and
computer for approximately 1/2 hr.,
I noticed the area above the compu¬
ter's regulator had become quite
hot. I disconnected the new supply
and printer and took some voltage
and current measurements.
Using the heavy duty 16K RAM
power supply and the computer run¬
ning, VDC at the input connection
was 10 and amps were .600 (600 mA).
With the printer's power supply,
VDC was above 11 and current was
above 900 mA. The supplied printer
power supply is a 1.2 amp unit.
The printer and computer work
very well together. DC voltage is
slightly above 9 volts and current
under 750 mA. My ZX80 with 16K RAM
runs cool and the power supply is
barely warm to the touch. I don't
understand why a 1.2 A supply is
required for the printer-computer
combo.
Paper is in short supply and
may take another month to arrive
after your printer. Mr. Finlay
said the paper comes from Timex in
Waterbury, CT. But when I con¬
tacted the Timex people, they said
they could not sell any paper to
me. When the printer goes on sale
here in the fall, there should be
paper available for all.
If you're desperate. Radio
Shack sells 4 1/2" paper that you-
could cut to 1-3' lengths and trim
to the required 4" width.
If you want to use the 230 VAC
supply that comes with the printer,
use this scheme. T1 is any small
transformer with a split 115VAC-
230VAC primary (two windings on the
primary, used either for 115 or 230
AC input) and good for 10 watts.
Multiply secondary volts by secon¬
dary amps to get approximate watts.
Leo Morgan, Peabody, MA
6
CAI peripherals allow you to expand your Sinclair
or MicroAce personal computer, enabling it to perform
like a main frame or host computer.. .a true stand alone system!
The CAI/O board, along with the tape, printer and phone
modem, can put you in touch with the rapidly expanding world of
computer communications. Shake hands with the billions of bytes of
information, entertainment and technical knowledge coming on
stream. Expand your horizons with quality peripherals designed specif-
ically for Sinclair personal computers.. .only from CAI.
CAI/O Board®
The CAI/O Board is the main interface that allows your personal
computer to communicate with the outside world as well as other
peripherals. No soldering or computer modification is required to
install the CAI/O board. Just plug it into the Sinclair’s expansion
port. The CAI/O board features:
Serial RS-232 Input/Output Port —RS-232 with hand shak¬
ing enables your Sinclair to communicate with other computers,
printers, and serial devices. Simple program commands allow you to
set baud rates from 110 to 9600. It’s compatible with modems that
allow you to interface your ZX80-81 with computer networks, such as
THE SOURCE®. Full details are available from CAI. The serial port
can also be configured to operate current loop devices, such as tele¬
types, etc.
Parallel I/O (3 Ports) —You can design circuits to light lamps,
control household appliances, power relays, run parallel printers, and
A/D converters.
Printer Port, Tape Port, and Memory Expansion Port—
These ports are on the CAI/O board to serve as the main interface
ports for other peripherals.
WIDGITAPE®
The WIDGITAPE system is a
stringy-floppy mass storage device that provides
much of the versatility of a floppy disk at a fraction of the
cost! The WIDGITAPE uses standard, readily available endless loop
cassette tapes (available from CAI at $2.95 per tape—tape lengths
from 30 seconds to 6 minutes). Each minute of tape allows you to store
up to 5.5K. WIDGITAPE functions are computer controlled. There’s
no need to operate the tape system manually. Program functions
include:
File Directory —WIDGITAPE has its own file directory which
can be viewed on the screen.
Read/Write —WIDGITAPE has the ability to read or write
data files during a program run.
File Extending and Modifying —Variables can be brought into
memory from the WIDGITAPE while a program is running and then
summed with other variables already in memory. These new variables
can then be written back into memory, printed, viewed $0095
on the screen... or all three!
Additional Peripherals From CAI
$|7Q95 64K Memory
X C ^ Expansion
Phone Modem
$12995
Programs Available from CAI
$795 Bio
RK yA ™$9 9s S rial $9 95Wi!
Package
Bang
Math
$1J,95 Home
Finance
CAI Peripherals
All CAI peripherals come with complete instruction manuals,
schematics, and a 30 day unconditional replacement warranty. Prices
are subject to change without notice.
$7095 When Purchased $/^095 When Purchased With
I *7 Separately ^JZ7 Additional CAI Peripherals
WIDGIPRINT® Printer
The WIDGIPRINT is a low cost, dependable 32 column thermal
printer that prints Sinclair’s alpha-numerics, graphics, and inverse
characters on 3.2" wide paper (readily available through CAI at $1.95
per 137' roll). The printer prints 190 words per minute, black on
white (so it’s easy to copy). It prints in three different program modes:
List —Lists the present program in memory.
Print —Will print script, variables, string variables, etc. from
within a program.
Screen Dump —This print mode allows present information on
the TV screen to be dumped to the printer.
I---
I Orders accepted by phone or mail.
I For mail orders, send check, money
order, VISA or MASTERCARD
■ numbers. Foreign orders must be
I made inU.S. currency.
Quantity
Description
Unit Price
Total
CAl/O Board
(See Price)
WIDGIPRINT
$99.95
WIDGITAPE
$99.95
OTHER
SUBTOTAL
Shipping and Handling
4% Sales Tax (Michigan Residents Only) _
TOTAL
CAI Instruments, Inc.
P.O. Box 2032
Midland, MI 48640
Phone: (517) 835-6145
Office Hours:
9:00 a.m.—4:30 p.m.
Evening Hours (Technical
Information)
6:00 p.m.—8:30 p.m.
SHIPPING AND HANDLING CHARGES
Within U.S. $5.00 Outside U.S.- F.O.B. Midland, MI
MasterCard/Visa___
Exp. Date__
Name__
Address_
City-State_Zip_
BOOK REVIEW
SS3FTSYIMC, ll\IC.
ZX81
SUPERMAZE —
SUPERMAZE 'S a three-dimensional maze program with
extraordinary full screen graphics that challenges you to
work your way through a complex labyrinth of corridors.
Enter SUPERMAZE at your own risk and carefully choose the
right combinations of passageways to reach the end in the
fewest possible moves
This graphically illustrated adventure game is full of
hazards to impair your ability to get through it. For example as
you wander through the endless corridors, you have to be
careful because there are hidden trap doors you can fall
through, finding yourself in another part of the maze
But SUPERMAZE also features some helpful devices to aid
your journey You can have a compass to guide you or stones
to drop along the way to let you know if you have already
passed through a section of the maze
Written with many machine code subroutines,
SUPERMAZE allows you to choose from ten mazes of
increasing difficulty In addition you can create and store
mazes of your own design
At the beginning of the program, you are given a choice of
options to play including:
• A map option to see where you've been but not where
you are going.
• An option to find and take with you gold bars in the maze
This helps you to develop skill in maneuvering
• Stones to drop along the way
• Optional randomly placed
trap doors
• The compass to guide you
LOAN/MORTGAGE
The LOAN/MORTAGE PROGRAM is a fast and flexible calculation program, useful as a
tool when contemplating a major purchase. It determines compound interest payments
enabling you to investigate the details of a fixed rate mortgage or many other types of loans
(i.e. Condominiums, cooperative apartments, car, boat, home improvements or college.) It is
also useful in developing payment schedules for all types of financial planning (such as
owner financing of real estate).
The program has a menu with seven items:
1. ) Single Payment Data indicates total payment broken down by interest and principal.
Also indicates principal balance at the time and total interest paid to date.
2. ) Single Year Date indicates total payment for any given year broken down by interest
and principal.
3.) Profile By Month indicates how much interest is due that month, total interest paid and the
principal balance.
4. ) Profile By Year totals the yearly interest payments (Helps you determine your interest
deduction so you can calculate your tax savings.) Includes total interest paid to date and
remaining balance. A useful tool to help you decide if you can afford the purchase.
5. ) Interest/Principal Plot graph compares principal versus interest payments over the
loan period
6. ) New Data allows you to enter changes or new information.
7. ) End allows you to SAVE the program with all your information and reload it at a later
date
16K $14.95
PLUS MANY MORE ZX81 PROGRAMS!
WRITE FOR FREE CATALOG
□ Please send me_copies of SUPERMAZE
@ $14,95 each.
□ Please send me_copies of LOAN/MORT.
> @ $14.95 each.
Please add $1.50 shipping & handling
New York residents add sales tax.
I enclose_.
SEND CHECK OR MONEY ORDER TO:
PO. Box 480, Murray Hill Station, New Ybrk, 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.
STATE/ZIP
Title: The Sinclair ZX81 Program¬
ming for Real Applications
By: Randle Hurley
Price: $17.95 (162 pgs, paper)
$24.95 (cassette tape)
Published by The MacMillan Press,
London, available from Mindware
Inc., 70 Boston Post Rd., Wayland,
MA, USA 01778.
This book is aptly billed as
being for people who want to get
down to business with their ZX81s.
It provides listings for serious
applications-—no games here. These
programs can be easily used for
many situtations you may have
thought required a !, real ! ' computer.
The book contains these chap¬
ters: Programming, Saving Time and
Space, Word Juggler (word proces¬
sing), Money, Personal Finances,
Banking, Bulk Storage (saving large
amounts of data). Rank Order (sort¬
ing), Exam Result Analysis, and
Hardware Modifications.
Programming covers how to
write, debug and document and
"idiot-proof" programs, but is not
a beginners' programming course.
Saving Time and Space offers excel¬
lent tips on efficient programming.
The program listings are quite
long (about 3K). I confess that I
didn't type any in to test them.
Randy told me of one error (if you
get this book, check that line 1520
on p.54 reads IF INKEY$="" THEN
GOTO 1520). But the listings are
not intimidating because they are
presented in chunks with excellent
documentation describing the pur¬
pose and method of each piece. You
can buy the programs on cassette.
Hardware tells how to build a
power supply, make Sinclair's 3K
RAM pack (never available in the
US) work, and wire a big keyboard.
The detailed documentation is
quite complete and clear. There is
life after the ZX81 manual—this
book can give you useful routines
and an education.—-AZ
8
EXCHANGING REGISTERS
(Part 6 of a series)
In addition to the eight
registers A,F,B,C,D,E,H and L
covered in an earlier article, the
Z80 (central processing unit in
your ZX80/81) has a twin set of
alternate registers. These
registers, named A',F', B',C',D',E',
H' and L', can only be accessed in
their paired state (ie., AF', BC').
As long as your machine code
routines are short, say 100 bytes
of code and data, you won't really
need to use an alternate register.
But sometime in your programming
future it may be easier to use one,
so let's examine the method of
switching information between them.
Without taking the time to
examine the register pairs you will
use, you can't know whether or not
your use of them will destroy vital
data. So before using registers,
PUSH them onto the stack to save
their data. Then POP them off
before returning to BASIC. This
way you can use these registers
during your program, but return
them to their original state before
exiting machine code. (Ex. PUSH
HL...EXX...PUSH HL...for using both
HL and HL'. Then POP HL...EXX...
POP HL...before RETurning. More on
PUSH and POP later.)
Only 6 instructions control
exchanging registers and alter¬
nates, but only 3 are really useful
in short subroutines:
EX AF,AF' exchanges data with the
alternate AF pair.
EX DE,HL puts data in Hl into DE
and data in DE into HL.
EXX exchanges data between BC,DE
and HL and their alternate pairs
(BC<->BC', DE < - >DE', HL<->Hl').
For example, suppose you have
two blocks of data, block 1 for use
in one branch of your subroutine
and block 2 for use in the other
branch. One solution is to load HL
with the starting address of block
1 and DE with block 2. Then,
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depending on a Test and Branch, HL
can contain either HL or, by
Exchanging DE,HL, HL can contain
"DE" for an INC HL loop.
Exchanging register pairs is
handy, but there is an easier way
to "save" ethereal data...
Next month: PUSHing and POPping
Jon Bobst, Zeta Software, PO Box
3522, Greenville, SC 29608-3522
Give your ZX81 (or 8K ZX80 with
video upgrade) something to do
while you're doing something else.
RUN this little program in SLOW:
10 PLOT INT (RND*6 4) ,INT (RND
*44)
30 GOTO 10
It randomly plots pixels until the
screen is totally filled.
Alexander Sloan, Green Bay, wi
To make it run a bit longer, add:
20 UNPLOT INT (RND*64),INT (RN
D*44)
9
NOW AVAILABLE
Keyboard.
x 'conversion
• 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 NOW $75.00
Add $5.00 mailing charge for continental U.S.
Other locations write for details.
Mail for information:
L.J.H. Enterprises
P.0. Box 6305, Orange, CA 92667
or call 714/547-8717
ADDING A JOYSTICK TO YOUR ZX81
The principle behind joysticks
is that the computer constantly
scans the keyboard. When you press
a key, you complete a circuit over
the matrix-wired keyboard. Take
the bottom off your computer and
you'll see two sets of connectors
where the keyboard plugs into the
computer. Connecting the proper
combination of keyboard leads simu¬
lates a key depression.
For this project you must use
a momentary contact matrix wired
joystick, not one using poten¬
tiometers. I used an Atari joy¬
stick. It is inexpensive and easy
to get (ask any dealer who sells
Atari game consoles). Unless you
have the proper complement connec¬
tor for your joystick, cut off the
end of the cable. The Atari stick
gives you 4 directions and a fire
button. This results in 6 wires, 1
common and 1 each for each position
and the button. Most matrix wired
joysticks have only 1 common and
fewer than 8 wires.
First, find the common. This
is the contact that, when coupled
with another contact and the proper
direction pushed on the stick,
completes a circuit. Use an ohm-
meter to check random pairs of
wires for their resistance while
moving the stick to all locations.
When the resistance drops near 0,
one of the wires is the common.
Locate the common by elimination,
then mark it with tape.
Now take the bottom off your
computer. With the metallic inside
of the bottom panel facing you and
the hole for memory expansion at
the upper right corner, look at the
right edge. At the location marked
in Fig. 1 drill a 1/4" hole. Put
some wood directly under where
you'll drill. From the outside,
stick the stripped wires from the
joystick through the hole.
With the heat sink in the
bottom right corner, look to the
left and find the pins shown in
Fig. 2. Solder the common to any
pin of KBDO-3. Solder the rest of
the wires to pins 1-8 (diodes 1-8
on schematic). Avoid solder drips
that cause short circuits.
With the bottom still off,
plug the computer in and hook it to
the TV. You should be able to
print characters to the screen by
moving the stick around. If you
get no response, carefully lift the
computer and press some keys. If
something appears on the screen,
the problem lies in a poor solder
joints or a faulty joystick. No
keyboard response means the system
is locked up from trying to read
more than 1 input. You have either
a short circuit where you soldered
or a faulty joystick.
If you don't have a joystick
and want an external control
button, you can wire any switch to
your computer. One wire must go to
KBDO-3 and the other to pins 1-8.
You can use INKEY$ to read
these inputs, but this is too slow
lO
for some programs. I use PEEK
16421. This doesn't give the char¬
acter code; translate it to fit
your needs.
This program demonstrates the
usefulness of your new stick.
First, determine the code for each
direction:
10 slou
2© LET R=PEEK 164-21
30 IP R =255 THEN GOTO 2©
4-0 PRINT RT 19,28;R
50 SCROLL
60 GOTO 2©
Try each position on the stick and
button and write down the number
produced. Now run this program:
10 CLS
20 LET X =30
3© LET Y=2S
4.0 SLOU
5® LET R=PEEK 154-21
6© IF ft= i CODE FOR UP) THEN LET
YsY + 1
7© IF ft = C CODE FOR DOWN) THEN L
ET V =Y -1
6© IP ft = t CODE FOR LEFT 5 THEN L
ET X=X-1
9S IF fi =(CODE FOR RIGHT) THEN
LET X=X+1
10© IP ft=(CODE FOR BUTTON) THEN
RUN
11© PLOT X,Y
120 GOTO 5©
Dave Straub, 500 Eastwood,
Petaluma, CA 94952
BASE OF ZX81
DO NOT SOLDER ABOVE DOTTED LINE
ZX81 BOARD WIRING SIDE
» EDGE CONNECTOR
BACK OF KEYBOARD CONNECTORS
"*■ o
o_, o_ o_o_o_ o_o_0_ °
o^ooooooo
8 7 6 5 4 3 2 1
DIODE NUMBER
4 3 2 1 0
KBD LINE NO.
Figure 2
REPORT FROM THE 3RD ZX MICROFAIR
The third ZX Microfair was
held 30 April-1 May 1982 in London.
Besides Sinclair's new Spectrum, we
saw some new ZX81 products.
The 5 1/4" disks promised by
Monolith and Macronics are now
available, at a hefty £225 price
tag. Macronics is now developing a
microdrive for ZX81s, probably
ready in August for £160.
Compusound showed an add-on to
put audio through the TV (currently
only for UHF). It adds a second
modulator, offsets the frequency to
generate a sound sub-carrier, then
mixes the two outputs.
Other hardware included joy¬
sticks from Micro-Gen (£9.60, 24
Agar Cres., Bracknell, Berks., UK)
and Thurnall Electronics (£12.95,
95 Liverpool Rd., Cadishead, Man¬
chester, UK M30 5BG). Micro-Gen
also has A/D converter boards. DCP
Microdevelopments offers A/D and
D/A add-on packs (2 Station Close,
Lingwood, Norwich, UK NR13 4AZ).
Many suppliers showed 16K RAMs
and big keyboards. RAM suppliers
suffered as Sinclair cut prices £10
at the show. Sinclair raised
printers to £ 59.95 as of 3 May, but
sold them for £49.95 at the show.
Sophisticated arcade-type and
board games abounded, as did new
educational software. We saw pro¬
grams to review history, physics,
chemistry and French. Most of
these programs are directly tied to
England's grade levels and testing.
Contact AVC Software, PO Box 415,
Birmingham, UK B17 ODH; Rose
Cassettes, 148 Widney Ln., Soli¬
hull, W. Midlands, UK B91 3LH.
Educational users might also con¬
tact EZUG (Educational ZX Users
Group), c/o Eric Deeson, Highgate
School, Birmingham 12, UK.
Two new ZX publications showed
up, ZX Computing and Sinclair User.
Contact ZX Computing, 145 Charing
Cross Rd., London WC2H OEE or
Sinclair User, 30-31 Islington
Green, London N1 8BJ for rates.
11
DEAR EDITOR
In response to a letter, AZ
writes that any mini- or micro¬
cassette recorder should work fine
with a ZX80/81. Yes and no. A
Sony Walkman-type recorder will
probably be no good because of its
low output voltage (it operates on
3 VDC). Check the DC operating
voltage before you buy—it should
be at least 6 VDC. Also, avoid
non-capstan drive recorders; gen¬
erally mini-cassette cheapies are
non-capstan drive. Further, micro¬
cassettes often don't do very well
aligning the tape and heads, so
treble response and loading pro¬
grams are touchy. And a recorder
that uses a permanent magnet
instead of an erase head should be
avoided on general principles.
Dave Taber, Menlo Park, CA
Permanent magnet erase heads leave
the tape noisier than high-
frequency erase heads. This noise
might cause loading problems.—KO
Users who install 16K RAM
packs may be surprised to find that
the ZX81 CLS function works more
slowly wih the increased memory.
Also, performance of some animation
programs becomes unacceptable. The
ZX81 manual indicates that the RAM
size threshold affecting the dis¬
play technique (thus the speed of
CLS) is 3328 bytes.
To provide the maximum amount
of accessable RAM while retaining
the fast CLS, adjust RAMTOP before
typing or loading programs:
POKE 16388,254
POKE 16389,76
NEW
Alfred Spencer, Framingham, MA
This technique sets RAMTOP (the
address of the last byte of RAM) to
76*256+254, or 19710 (multiply
first). You now have 3326 bytes,
or about 3.2K to work in.—AZ
A simple suggestion other
readers may not have thought of—
Say you're entering a long program
and you wish to jump backwards or
forwards to a far-away line. Even
in the FAST mode this takes a lot
of time and punching. Just enter a
blank line number which you are
sure is not already in the program.
For example, enter 3501 or 3509
when you want to get to 3510. The
line cursor goes there in one shot
as it "erases" a non-existent line.
Ken Kenny, Vancouver, BC, Canada
The ZX81 does not handle nega¬
tive numbers normally. Try this:
10 LET A=-5
20 LET B=3
30 PRINT B**A
40 PRINT SQR A
Lines 30 and 40 give error A/line
number. According to Sinclair, the
ZX81 won't raise negative numbers
to a power (like -X**B) because it
doesn't differentiate between the
exponent as an integer and a real
number. To assign the value A**B
to C where A may be negative and B
is integral, instead of LET C=A**B,
they suggest using LET C=ABS(A)**B
* (1 - (B-INT (B/2 ) * (1-A/ABS (A))).
I use the method in this
example program for exponentiation
if A might be a negative integer.
This routine converts A to ABS A
(always positive) and sets a switch
SW to 1. The value of SW chooses a
PRINT statement reflecting the true
effect of -A:
100 LET A=-9
110 LET SW=0
120 IF A<0 THEN LET SW = 1
130 IF A<0 THEN LET A=ABS A
140 LET SQ=A**2
150 LET CUBED=A**3
160 IF SW = 1 THEN GOTO 190
170 PRINT "A**2 = ";SQ,"A** 3 = " ;CU
BED
180 STOP
190 PRINT "A**2 = ";SQ,"A**3 = -";C
UBED
12
William F. Tracy, Donelson, TN
For do-it-yourselfers, 50-pin
gold wirewrap edge connectors are
available from Digi-Key Corp.,
Thief River Falls, MN 56701. Their
part no. C6-25, $4.08 in single
units. Cut off the ends and pull
out the appropriate pins. Use some
of the plastic from the ends to
make a key and glue it in.
Bob Berch, Rochester, NY
I was spending hours unsuc¬
cessfully trying to SAVE and LOAD
programs. I traced the problem to
the tape jacks on the ZX81. The
jacks do not lock the plug firmly
into place. I removed the jacks
and substituted Radio Shack ones
designed for thru-mounting. They
are self-enclosed in a small plas¬
tic case with rear solder con¬
nections. I used a solder lug bent
at a right angle to mount the jack.
One end of the lug was soldered to
the circuit board and the other was
used to mount the jack. Take care
to position the jack so the plug
can be inserted properly. I
soldered a short jumper in the rear
for the HOT side connection. A
ground was not necessary since the
ground lug did the job.
Ron DeBalko, Wilkes-Barre, PA
Data names use far less
storage than constants in your ZX
computer. Thus using the name NO
instead of the number 0 saves five
bytes of RAM. One must, of course,
take into account the RAM used to
hold that variable and the program
line which generates it.
Checking through one of my
programs, I found the number 0 was
used 44 times. Establishing the
variable name NO, for example, and
setting it equal to 0 saves over
200 bytes of storage even if you
include the extra space needed to
store the variable. Of all numbers
used 3 or more times in this
program, putting an "N" before the
numeral (thus converting it to a
variable name) and then setting
that variable to the number it
represents saved 1240 bytes. (My
program used 34 different numbers
occurring 305 times.) At the end
of memory, 1.2K looks like a lot.
If storage space was scarce to
start with, don't waste your
savings on program lines creating
these new variables. Rather set
values by entering commands such as
LET N0=0 with no line number.
John L. La Pin, Germantown, WI
USERS' GROUPS
Here's the list of users' groups
that have contacted us this month.
To list your group, drop us a line
or give us a call at 617-456-3661
and we'll send interested people to
you. If you're looking for a group
in your area, send a SASE. We'll
send what information we have.—AZ
New Orleans, LA: Contact Tom
Fussell, 13721 Chef Menteur Hwy.,
#219, New Orleans, LA 70129, 504/
254-4425.
New York, NY: Contact ZX Users
America, Michael Wilson, 626 Water
St., New York, NY 10002.
North Alabama: North Alabama
ZX80/1 Users Group, Bob Boyer, 1103
Rivlin Rd., Huntsville, AL, 883-
4354 evenings.
UK PRODUCTS LISTING
Want to know first-hand what's
happening with British ZX hardware,
software and publications? We have
a limited number of official show
guides from the 3rd ZX Microfair,
held 30 April-1 May in London.
This 69-page book lists 79 ZX sup¬
pliers with product descriptions
and prices, many not available yet
in the US. Guide also includes
some program listings and tips.
Send $2 to SYNTAX Show Guide, RD 2
Box 457, Harvard, MA 01451.
13
NOW, THE BESTSELLING
HOME COMPUTER PACKAGE
IS AVAILABLE FOR THE ZX81
Why is THE HOME COMPUTER PACKAGE a bestseller? Judge for yourself:
BILLBOARD
Your message scrolls
continuously across
the screen in giant let¬
ters. Perfect for dis¬
plays and exhibits.
Messages are easily
changed. Press “S” to
SAVE a message on
tape. When reloaded, it
comes up running.
COMPOSER
A color keyboard overlay turns your com¬
puter into a multi-octave musical instru¬
ment. Broadcast music to nearby radios
as you play — or play through your own
sound system — or record directly onto
tape. Stores notes as you play, ready for
immediate playback. EDIT keys allow
easy changes. Single-step forward or
backward through your piece. SPECIAL
EFFECTS keys let you create laser blasts
and arcade noises.
CHECKBOOK BALANCER
Keep a running tabula-
ETCH-A-SCREEN
tion of your bank ac-
Easily paint text and graphics over most of
count. Reconcile bank
the screen. Move forward, backward, up
statement to check-
or down, leaving behind text, graphics,
book balance and dis-
and inverse characters. Keys REPEAT
play both. Stores and
while held down. Your drawing can be
displays up to twenty
stored on tape... and immediately ap-
uncleared transac-
pears when reloaded. Perfect for desig-
tions, (more on larger
ning screen logos or just doodling.
memories).
The complete ZX81 HOME COMPUTER PACKAGE, including cassette
of four programs, manual, guide cards, screen display sheet, musical
score sheet, and TWO FULL-COLOR KEYBOARD OVERLAYS, is just
$9.95. Shipping and handling included!
$ 9.95
From: LAMO-LEM LABORATORIES, CODE 114 BOX 2382, LA JOLLA, CA 92038
The ZX81 Home Computer Package, ($9.95)
— ■ similar items: ■ ■ - ——
The ZX80 Home Computer Package
(for standard 4K ROM), ($9.95) .
The Timex Sinclair 1000
Home Computer Package, ($9.95) .
■■■ . also available: —
ZX81 Classics (with K-Trek, Life,
Lunar Lander, Mastermind), ($9.95)
ZX81 IK Disassembler, ($9.95) .
TOTAL
The ZX81 Home Computer Package runs on
allZX81’s, (IKmemory or more). Also on
ZX80’s with optional 8K ROM. Enclose check
or money-order with or ders. No postage, han¬
dling, or sales tax. Foreign orders add 30%
for airmail. All packages carry ten day re-
fund-or-replace guarantee.
Our catalog, with screen display and coding sheets, is free!
NAME
ADDRESS
STATE/ZIP
/""" BANI-TECH \
Software of the Month Club
Get the most from your ZX81 with 16K, use it to
its full potential, while building an impressive in¬
ventory of software. Receive twelve listed 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___
Name __
Address___ !
City--State_Zip_
--- -- ^
EXPANDING EXISTING 16K PROGRAMS
If you upgraded to 48K RAM for
your ZX81, you may think it simple
to add a few program lines and en¬
large the variable arrays in exist¬
ing 16K RAM programs to utilize the
increased memory capacity. If you
try this by setting RAMTOP to 65280
(for 48K RAM) and entering RUN, you
get an error 4—not enough memory.
To understand what happens,
refer to the ZX81 manual, chaps.
27&28. Note memory is partitioned
into variably sized areas for stor¬
ing different kinds of information.
Before a program is entered, the
area called SPARE occupies most of
memory. As the program goes in,
the area between D FILE and STKEND
shifts upward and SPARE becomes
smaller. Above SPARE are 3 addi¬
tional areas, MACHINE stack (whose
address is pointed to by ERR SP),
GOSUB stack (whose beginning is 1
byte under RAMTOP), and USR rou¬
tines (of no concern now).
When you enter a 16K program,
RAMTOP is set at 32768, unless you
choose a different value (see chap.
26 of the manual). ERR SP is set
exactly 4 bytes below RAMTOP. The
area between ERR SP and RAMTOP is
reserved for the GOSUB stack. As
the program runs, this area expands
and contracts as the program goes
to or returns from subroutines.
Since RAMTOP is a normally
fixed value representing the first
non-existent byte of memory, the
first byte of the GOSUB stack is
normally the last byte of RAM.
Thus no provision is made to adjust
the GOSUB stack even if RAMTOP is
changed. So LOADing a 16K tape .
into 48K RAM does not automatically
expand the available space.
Fortunately, the situation is
easy to fix with a few entries in
the immediate mode.
1. To set RAMTOP at the desired
value (assumed to be 65280 here):
POKE 16388,0
POKE 16389,255
NEW
2. Test the RAMTOP value you just
entered by:
PRINT PEEK 16388+256*PEEK 16389
This should give the value 65280.
3. LOAD your taped program in
the normal way.
4. Enter in the immediate mode:
POKE 65279,62
POKE 65278,0
POKE 65277,6
POKE 65276,118
POKE 65386,252
POKE 65387,254
These are the initial values that
would exist had the program been
entered with RAMTOP set at 65280.
5. Now clear the initial GOSUB
stack and the first line of the
machine stack. Enter:
POKE 32767,0
POKE 32766,0
POKE 32765,0
POKE 32764,0
You are now ready to expand that
16K program.
R. Hensley, Riyadh, Saudi Arabia
15
HARDWARE PREVIEW—RD8100 SYSTEM
Products: RD8100,1 motherboards &
RD8110-80 modules for
controller applications
From: Mindware, 70 Boston Post
Road, Wayland, MA, 01778
USA. (US distributor)
Prices: Super MUM $99.50
Micro MUM $44.95
Modules $74.95-84.95
When you want to try an idea
quickly, these modules eliminate
hardware problems that get in your
way. Every setup I tried worked
right away.
SYNTAX doesn't review proto¬
types, so let's call this a pre¬
view. Hardware we saw is not
available in the US until the end
of June. Module packaging could
change, but we expect the mother¬
boards to remain the same. This
hardware is now sold in the UK.
RD8100 motherboards and mod¬
ules are building blocks that plug
onto your computer or together to
create instant systems. Modules
resemble cassette cases with con¬
nectors on the long, thin edges.
Two-module MUM-boards are flat PCs
that plug into your computer's
expansion connector. Super-MUMs
hold 8 modules and provide an
attractive sloping case that fits
behind your computer. Super-MUMs
fully buffer the expansion bus;
both expanders let you connect the
ZX printer and memory modules.
Documentation for the system
we previewed is small, consisting
of typewritten pages reduced to 4"
x 6". Despite the difficulty in
reading it, the information was
complete enough for our tests.
We spent several hours looking
at and trying the equipment. We
saw everything but the light pen,
and tried the On-Offer and the
Volt-Catcher.
Mechanically the modules and
motherboards look and feel good.
The PC boards use low technology—
wide traces and large separations.
Since the modules are sealed, we
couldn't see internal construction,
but we could see how the mother¬
boards went together and they seem
well done. Modules slip easily
onto the Molex KK-type pins of MUM-
boards, making all necessary bus
and power connections. Sockets at
the top accept poke-in wires to
connect external devices. My com¬
plaint is that the module addresses
are on the side of the module where
I cannot see them when they are
assembled into a system.
Test features built into the
module tops simplify testing. LEDs
indicate the state of the output
port, for example. Most modules
flash a green LED when addressed, a
major convenience in testing.
We tested the I/O port, and A/D
converter functions. In a few min¬
utes, we were able to connect a
pot between 5V and 0V and write an
8-line program to read DC volts,
convert the 0-255 data to 0-5V for
screen printout, test against a
half-scale limit, turn on bit 4 of
the output port to drive a beeper,
and wait for a keypress to turn off
the alarm and retest the voltage.
Our digital voltmeter read the DC
voltage simultaneously and accuracy
seemed reasonable though we made no
attempt at calibration.
All our tests were run with
BASIC PEEK and POKE instructions,
so operation was slow. We did not
verify RD Lab's claim that machine
language would be faster, but I
believe it.
Mindware tells us that a real¬
time clock module is currently
being debated. I cast my vote for
a 24-hr calendar clock (day, hour,
min, sec) with battery-backed
timing—useful for business and
laboratory applications.
Cost of parts to build any¬
thing you would assemble from these
modules would be a fraction of the
cost of one module. What you
really buy with RD8100 components
are hassle-free hours when you want
the result rather than the building
experience. —KO
16
SOFTWARE REVIEW
Program: Adventure A
Type: Game
ROM/RAM: 8K/16K
Price: $19.95+1.50 post & hand.
From Softsync Inc., PO Box 480,
Murray Hill Station, New York NY
10156. Written by Artie Computing
and published by Melbourne House,
England.
Adventure is not for impatient
or unimaginative players. It has
no bombs, no graphics, and no
split-second decisions. It is an
intellectual game requiring thought
rather than reflexes.
It works like adventure games
on bigger micros—the computer des¬
cribes your situation, and you must
tell it how to proceed. You move
through fantastic places, acquiring
items to protect yourself from
hazards while trying to return
safely to your spaceship. You
direct the computer in simple
English sentences. This dialog is
part of the game's challenge—
deducing the computer's vocabu¬
lary—while also making it
relatively easy to play.
This self-starting program
comes on cassette with an instruc¬
tion sheet offering hints (but not
enough). My copy loaded the first
time. I tried to break into it to
see the listing, to no avail. I
also could not crash it.
I also could not beat it.
Fortunately, you can type QUIT at
any point and exit. I bailed out
of the maze, the pit, the prison
cell, and the old house in one sit¬
ting, never coming near finding my
spaceship.
In short, this game impressed
me. The machine's reaction time is
quick, the possibilities intriguing
and it's tough to beat. It's a
good exercise in logic and strat¬
egy, though be warned it can be
frustrating. Softsync also offers
Adventures B and C for the truly
masochistic.—AZ
ANNUITY—8K/1K
This 8K ROM/IK RAM program
calculates the payments needed to
pay off a loan or how many years it
takes to pay off a loan at a fixed
payment. If the fixed payment
would never pay off the loan, an
error code A results.
Suppose you wish to finance
$50,000 for 30 years with an annual
interest rate (APR) of 12%. In
response to the prompts, enter 1
for payment, 30 for years to fin¬
ance, 12 for payments per year, 12
for APR, and 50000 for loan size.
Your monthly payments are $514.30.
Or you wish to finance $5000
at 14%. You can afford $200 per
month. How long will it take to
pay off the loan? Enter 2 for pay¬
off years, 12 for payments per
year, 14 for APR, 5000 for loan
size, and 200 for payment. You'll
need 2.4774869 years.
R. Townsend, West Fork, AR
10
NT E R
PRINT
1 **
R 1
x* t i j : ‘ru M
FHYHtNf E
£© PRINT
fiRS ENTEh ■
30 INPUT
4-S CL5
ri I
Q
2 „t 1 ' l~ Li hi
5©
TST tTs
2 T
HEN GOTO
3 ©
60
78
PRINT
INPUT
HT
Cj -j - “yp s c
a J O 1- -L.NRN
38
PRINT
fiT
S' ; I ; E: HOW
ITHNY PHY M
£ NTS P £R VEHPT 5 5
s@
INPUT
100
CL-5
110
IF O ~
T H
E N
£5l* hi O
X o ko
120
LET N
130
PkTITT
fiT
O c Q
: i: rd
-- V ! 5
14 0
T> 4 jpji nr
H
'1 CTA
168
L.U! JL
— f* / i
$.2. i
1 f'©
PRINT
FIT
- s 5 §
f4 f*-J S J 7 F y s E
-7
J.. O
INPUT
r-=
190
200
IF O -
2 1 FI
pr kj
fi OT O
;~= rr £5
2 1©
LET 3
= j/ (
:?. — (
4- X ?
IT — I vj )
22©
L. ET P
r ( Tf\i
t
-¥• R
X 0 0 j J / 3. 0 0
2 -3 0
$ 1 ' j P
OK TM7
fiT
: - : h Li
U H I—' H Y H E NT —
iC? *£•
STOP
25©
f-' .9 IN f
M~!
S , l
; : - p
v HP NT =-.' "
2&s5
INPUT
fT*
2 t'8
ij 1_. t>
k*38
(1 + 13
L ET M
= U - IN
1 K
2 ' l H -
S X 13 j .3 i L H
29©
I. ET N
3©©
PRINT
pti
9 „= 1
_L ?
**; N j
■. Y r< 5
310
5 i Of
SYNThCT IC SUM : 3 /82y
17
LOADING HEXADECIMAL LISTINGS—8K
Have you ever skipped a
machine code (MC) program because
use the BASIC loader program given
with it looked hard? Here is a
solution. To use a hex MC listing,
just type the hex codes into a REM
statement. This program converts
the hex and stores it into a space
explicitly for it.
As an example, look at this MC
program to add 10 and 20 in hex:
HEX ASSEMBLY COMMENTS
3E 10 LD A,10 ;first number
06 20 LD B,20 ;second number
80 ADD A,B ;A=A+B
06 00 LD B,00 ;B=00
4F LD C,A ;BC=00xx
C9 RET ;return
With a listing like this, you'll
often find a loader program to help
you enter the code. It usually
asks you for a start address (where
to put the code), then lets you
type in hex (or decimal). The
lines you enter appear on the
screen and scroll. As you type in
codes, the computer POKES the
binary equivalents into successive
memory locations, usually in a REM
statement.
This method has several draw¬
backs. First, whenever you want to
use or test the MC, you must use
the loader and type it all in
again. Second is the messy REM
statement. You often have to type
in something like:
1 REM (437 spaces)
just to use other loaders.
Third, you must be careful not
to LIST the program, or that REM
line might crash the system.
To use our example program
with the XFER loader (listing
follows), type in these two lines,
with the XFER program itself:
10 REM ( 3E 10 06 20 80 06 00
4F C9
20 REM $
RUN. After it loads your MC, it
will GOTO 1000. The code at 1000
executes your machine code via a
USR statement. The way the code
SYNCH ROSETTE
FOR THE ZX-80 & ZX-81
8K ROM IK - 16K
GAM ES-EDUCATIONAL-BUSI NESS
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 & S CO.
388 West Lake Street • Addison, IL, 60101
(312) 628-8955
runs gives you these features:
1. You can place your MC REM
lines anywhere in the program, as
long as they each open with a (
character, and the set of them is
eventually followed by one REM $
statement.
2. Any number of spaces may pre¬
cede or follow the hex codes. But
do not put any spaces before the
opening ( or the terminating $
after REM.
So these lines are legal:
10 REM (3E 1006 20 80
20 REM ( 06004F C9
30 REM $
You may also interleave any number
of BASIC lines (including standard
REMs) with your hex code REMs. The
same rule applies to the REM $
statement. The only restrictions
are that the lines must appear in a
linear order and you must not split
the hex codes themselves (ie,
inserting spaces between the 2
digits of a single code).
If you make a mistake, just
18
«r
edit the REM statement as you would
any BASIC line.
XFER fills a string variable,
Z$, with binary bytes of MC, con¬
verted from hex. Note the LET Z$
at line 110 m ust be the first
assignment (LET) statement executed
in the program. Be sure to use the
token for REM in line 330. Type
330, then REM (E key), then back¬
space with the left arrow key and
type IF X$..., then move with the
right arrow key to finish the line.
REM
II® LET
120 LET
14-e LET
1 * 256+3
200 REM
210
220
230.
S4-®
a i->.
XFER
z$-'- **
R=16513
Sft=PEEK
164-00 +PEEK 164-0
rift.
OOP
G05UB 30©
IF X f ='' l FHEN
£*~ X$ = ”s:“ T HFhi
©OXO'£00
REM FIND ft REM
310 LET ft=ft+5
320 LET X=PEEK ft
325 LET XS-CHRS X
330 lF X $— ’ 5 REM 1
•34-0 LET ft =ft + 1
350 IP PEEK ft= 11 S
360 GOTO 340
3/0 LET h=h +1
>0505 4-00
;oto 10@0
THEN GOTO 375
THEN GOTO 306
380 LET X -PEEK ft
385 LET Xt=CHRt X
320 RETURN
4-00 REM PROCESS ft LINE
418 GOSUB SO©
428 IF EOL-1 THEN RETURN
438 LET H =(X-2S5 +16+PEER ift + i> -
28
448 LET ft =H +1
458 LET Z$=Z*+C HR$ H
468 GOTO 480
588 REM FIND ft NON-SPftCE CHRP
585 LET EDL -8
518 LET ft=ft + I
528 LET X-PEEK ft
538 IF X=© THEN GOTO 51©
548 IF X =118 THEM LET EOL=i
558 LET X $ --CHR $ X
580 RFTi jDM
1888 REM DONE WITH XFER
1818 LET URLUE-USR 3ft
SYNTACTIC SUM: 43503, SK
To place machine code in the
first line (REM) of the program,
make these mods:
delete 450, 140
130 LET D=16514
140 LET SA=D
450 POKE D,H
451 LET D=D+1
When you want to call your machine
code, use a USR call to SA. This
is illustrated in line 1010.
If you enter the example MC
program here, change line 1010 to
PRINT USR SA. The answer should be
48, which is 10+20 in hex.
David Ornstein,
Heuristics,
Newton, MA
NUMBERS HELD INEXACTLY ON THE ZX81
(Part 4 of a series)
The ZX81 doesn't hold simple
decimals like .5 & .25 exactly.
That is because (1/10) expands as
(1/8)x(8/10), ie, as 2 ^ times . 8 ,
or 125 76 204 204 204, ... (where
the 76 also stands
plained earlier.)
display the 5-byte
tion of a number:
10 INPUT X
15 FOR U-i TO s
LET O = P tiE K 16480 +255 *PFFK
for 204 as ex-
Use Program 1 to
ZX81 representa-
28
64© 1
38
4©
P©
6©
78
LET' jf €_.! 4 - . f
PRINT PEEK I;” -- ;
NEXT U
PRINT
GOTO 10
so .1 has no exact representa¬
tion as a binary number. Its best
approximation is 125 76 204 204 204
in 5 bytes. But the ZX81 doesn't
round up the quotient after divi¬
sion in a case like this. It holds
0.1 as 125 76 204 204 204. Hence,
0.5 is held as 127 127 255 255 255
instead of the exact result 128 0 0
0 0 and .25 is held as 126 127 255
255 255 instead of 127 0 0 0 0.
(why SQR .5 and SQR .25 were
affected by the old 8K ROM bug).
To hold these fractions ex¬
actly, write them as 1/2 and 1/4
(or 5/10 and 25/100). If all else
fails, take a few weeks' holiday
and master machine code!
This program gives best
results (exact wherever possible)
for all these decimal fractions:
18 LET X=©
2© LET U=PEEK 164 ©8+256 *PEEK ’
64© I
"ENTER ft NUMBER THftT
w : hhls y j. Tn h DEOIHPL POINT own
CONTftINS NO E-FORMhT”
4©
5@
6©
"7
80
98
18©
INPUT
LET B
1 er s
:~-s— f t_
L ET' D
F ’. r-, —
r\
LET
HEX'
B =5
t n
- N B S
r> :
1
1 "
3 S*,
19
110 LET X=U RL
IS© FOR X =U 4- 1 TO U-f-5
13© IF URL B$”D*X>=2^^32/2 THEN
POKE U +5,PEEK (U+5) +1
14-0 PRINT PEEK X;
15© NEXT I
160 PRINT
IT© GOTO 4-0
With this program, .5 now gives 128
0 0 0 0 , an exact answer, .25 gives
127 0 0 0 0 , an exact answer, and
best 5-byte approximation. A bit
surprisingly, .0000000000009094947
018 gives 89 0 0 0 0, which is
exactly 2 . The ZX81 is full of
pleasant surprises!
Frank O'Hara, Surbiton, Surrey, UK
SCREEN BACKGROUND FOR GAMES
CLASSIFIED ADS *
Reach thousands of ZX80/81 owners!
Send your ad, typed 35 char/line,
with check to arr ive by the 15th
for next month's issue. Ads arriv¬
ing after the 15th appear in issue
after the next month. Ads are $9
per line and must be resubmitted
for each month. No phone orders or
credit cards. We take no respon¬
sibility for advertisers. SYNTAX,
RD 2 Box 457, Harvard, MA 01451.
ZX81 Software for lk or 16K RAM!
Games,Business,etc- Accessories
Great Lakes Software,201 Burlington
Road, Valparaiso IN 46383
A dark or solid background
often gives a better effect for
printing or plotting in games.
With an 8K ROM and 16K RAM, an
almost instant background is
possible in BASIC.
Here's how the following lines
work. First, pick the character
you want to fill the screen with.
Then by filling the array A$ with
this character, you lengthen the
string to 704 bytes (exact screen
size). When you enter PRINT A$,
you'll get an almost instant screen
fill. Before printing your string,
enter PRINT AT 0,0; (line 90).
This lets you start printing at the
first byte of the screen.
You can store this string on
tape or in your program as long as
you don't type CLEAR or NEW. After
running the program, you can delete
all the lines and then use the
string in another program. For a
nice effect, try using an inverse
space and then unplotting a line.
TWICE THE MEMORY, INCREASED SPEED
The 6116 2K x 8 150ns Static Ram
available for immediate delivery
at a cost of $19.00 $1.00 for
shipping. Full instructions for
ZX81 installation. Send check or
MO to: SUPPORT SYSTEMS ONE, PO
BOX 1794, Phila., PA 19105
MORE GAMES FOR YOUR ZX81...
Five IK programs.$10.
Bandit, Chase, Life, Pong, Skeet.
Any two 16K programs.$10.
Bong
Checkbook
Solitaire
Biorhythm
Backgammon
Cat and Mouse
Guess the Animal
Craps
Hangman
Checkers
Blackjack
Stock Market
Klingon Wars
3D TicTacToe
— all programs on cassette tape —
Send check or money order to:
BIOCAL SOFTWARE
340 Cypress Drive
Fairfax, CA. 94930
Paul Qualls Jr., Amarillo, TX
I© FR5T
2© DIM R$ C704-i
30 INPUT h$
4-© FOR F = i TO 704-
5© LET Rf ( F)
6© NEXT F
7© PRINT RT O,©;
SO PRINT R$
90 PRINT hT 0 , 0 ;
SYNTACTIC SUM; 6678, 8K
ZX-81's FOR SALE $145.95 & $4.95
for shipping and handling. New,
complete,tested,in stock and ready
to ship. 80 day warranty. C.O.D.,
certified check,VISA/MC we can
expedite delivery. National
Electronics III 10425 Kingston Pike
Concord, TN 37922 1-615-690-8927
Hrs: 10-6 M-F 10-5 Sat.
20
CP PRODUCTIONS
Demogogue Adventures
Tower of Survival .$25.95
Castle of the Sorceror. 20.95
Sea Battle.15.95
SAT Vocabulary.15.95
BASIC Computer Programming.... 15.95
Send check or money order to
CP PRODUCTIONS 146 S. Coffeen Ave.
Suite 141 Sheridan, Wyoming 82801
Send for free catalog
FOR FREE INFORMATION on educational
software & data loading monitor.
Send long SASE to Edson Electronics
P.O. Box 151211, Tampa, FL. 33684
Zilog Z80A CPU Tech Manual $7.88;
Zilog Assembly Lang Prog Manual
$15.75; Crash Course in Microcompu¬
ters $19; ZX80 Pocketbook w/8K
supplement $16.45; 4K Annotated ROM
list $40; back issues of SYNTAX $4
ea. All include shipping. SYNTAX
RD 2 Box 457 Harvard MA 01451.
New program finds vertex and points
in quadratic equations, solves two
variable equations, plots points in
two variable equations, and more.
For tape send cash or M.O. for $8
to Van Kirchhoff, RR1 Box 21, Brid¬
geton, NJ 08302.
** THE EXPANDABLE ZX80 AND ZX81 **
* More than a book of hardware *
* projects. Only 9.95 + 1.25 p&h *
* To: Box 1222 ShowLow Az 85901 *
FOR SALE ZX81 (no kit), 16K RAM,
Sinclair software Jr Ed I and Games
II. $175.00 W. Hulett, 4331 Deer
Creek Dr., Jackson, MS 39211.
FIFTY NIFTY PROGRAMS FOR YOUR ZX81!
Book has 50 Top Quality LK programs
w/instructions+comments. Full of
GAMES/GRAPHICS/FUNSTUFF. ONLY $7.95
LEE CARTER Bx 246 Harrison,ME 04040
********* L Q T g Qp GRAPHICS**********
LAND THE SPACE SHUTTLE and LAND/AIR
BATTLE. Two games on one tape.$8.95
*NEW* SPACE BATTLE. On tape...$6.95
Above games for ZX81/16KRAM*FUNWARE
7119 Santa Fe Av. Dallas, Tx. 75223
Sale:Security Program-protect prog¬
rams and files;makes*them nonlist-
able or editable;must enter code to
use;on cassette;send $15 to Mark
E.Rogers ,Rt. 2 Box 221-H,Saucier,
Ms. 3 9574
ADD ON MEMORY for ZX80/81: 16K
Memory assembled and tested. No
extra pwr/supply needed. 90 day
warranty on parts & labor.$65.95
PPD, check or money order only:
CA residents add %6.
KB Enterprises
PO Box 271173
Escondido, Ca. 92027
FREE CATALOG! FLIGHT SIMULATOR $10
accounting spreadsheet programs $35
african pilot:arcade adventure $10
Hensley, Box 334, Asheboro NC 27203
OVERHEATING HAVE YOUR ZX81 DOWN?
You need an improved heatsink.
For info send SASE to: B. Sanzone
289 Baxter Lane Milford CT. 06460
AT LAST! THE ULTIMATE DUNGEON GAME
for 16K ZX81! Labyrinth of Qazxl is
a multilevel semitext dungeon that
maps what you see! Find treasure,
fight monsters(9 kinds), gain exp¬
erience, move up levels. $18 US;
+ bonus dice game. Send MO in $CDN
to JLK Software, 6 Dufferin Place,
St. John's, NFLD, Canada, A1A 2V1
Mom ROM got you down? Put HOT Z in
your ZX81 and become master of your
own black box. HOT Z takes the
drudgery and mystery out of machine
language: cursor driven, labelled
listings, easy edit functions,
assembly, standard Z80 mnemonics,
and fast response. Easily expanded
and personalized. No BASIC. Needs
16K and SLOW. Cassette with over
40 pages of documentation: $19.95
SINWARE, Box 323, Dixon, NM 87527
OPERATE MORE THAN ONE CAR? ZX81/16K
listing to track time/mileage of 4
maintenance items on 3 cars. Send
$1.00 and SASE to: Johnson, 9806
Longview, Ellicott City, MD. 21043
21
2 PLAYER FLICKER FREE GAMES WITH
PLENTY OF GRAPHICS FOR THE ZX81 IK
TANKS: Destroy opponents tank or be
killed. SUBS: Launch subs,but mines
ARTIST: Draw your own pictures.List
ings $5 ea or 3/12.M.Dmytryshyn 56
Riverwood Pkwy Toronto Can. M8Y 4E5
ZX81 keyboard tactile feedback,
touch typing possible, helps stop
missed keys, simple to install
overlay. $3.95 P.Hargrave,Site V,
RR4,Nanaimo,B.C.,V9R5X9,Canada
WE CHALLENGE THE SOFTWARE COMPANIES
TO LOWER THEIR PRICES!
Biorhythms 8K ROM/lK&up.1.00
Graphics Billboard 8/lup.1.00
Horse Race 8/lup.1.00
Spinner T.M. (like Rubik 1 s)8/16.1.00
Improved ZX81 PAUSE.1.00
Linear Regression 8/lup.2.00
SASE get you our GOODIES CATALOG
Order gets you!!FREE!! PROGRAM
EZRA GROUP II
EZRA GROUP II
POB 5222 San Diego,California 92105
**** Kits *** Kits *** Kits ****
Enhance your ZX81 with these
palm-sized Plug-On Boards!
The CX81 : Enables you to quick¬
ly load up & display photoimages
DOT FOR DOT on your TV!
The RX81 : Allows computer con¬
trol over 8 inputs/outputs. Add
relays for your own applications!
The LP81 : Light Pen. Imagine
being able to draw and erase di¬
rectly on your TV screen!
** Any Kit $ 49.95 less case **
** Requires soldering,2K Mem.**
ZODEX
EASTHILL,OAKHAM,MAO10 6 8
*******************************
COMING SOON! "TRADER JACK"
16K RAM - Imported from the U.K.
Fantastic - Beats Rubic's Cube!
Polynesian Trader - Inter Islands.
Hazards,Profits,Losses,Storms.
Savage Software PO Box 892
New Smyrna Beach, Florida 32069
THREE-PORT 8255 based I/O board
with 16K RAM edge connector, $45.
Professional Electronics,109 Ches-
ney Lane, Columbia,S.C. 29209
***********************************
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
***********************************
"Original MicroAce 4K keyboards
Easy to replace.$2ea. or 3 for $5.
Also have the following misc. parts
4K MicroAce cases($10),Microace
plastic pieces to hold PCboard+case
together (3sets$l.50), ZX81 Manual
($10)and 4K MicroAce keyboard($12).
Write for addt.parts available for
the MicroAce. Send check to:Bob
Ward 3176 Oak Knoll Los Alamitos
Calif. 90720
MEDIEVAL FANTASY (on tape) $9.95
Animated graphic displays of 8
different monster battles;Forays
into the crypt;Retreats to the town
(ZX81/16K RAM) ck payable-A. Daw.
78 Aberdeen, Clayton MO 63105
COMING SOON! "ZX81 MONOPOLY" (C)
16K RAM - up to 6 players- imported
From the U.K. Spanish Board Version.
Savage Software P.O. Box 892
New Smyrna Beach, Florida 32069
7 GAMES on CASSETTE—IK $10-16K $15
Mastermind,Doublemind,Slot Machine,
Craps,Tic Tac Toe,Sub Rescue,White
Hot Number. NEW ENGLAND SOFTWARE,
P.O. Box 691, Hyannis, MA 02601
22
-FANTASTIC SPACE WAR GAME !-
X-81 SPACE RAIDERS for ZX81 w/ 16K.
ML graphic and math routines create
fast, exciting, accurate simulation
of space navigation and battle.
$19.95 for cassette, manual, and
keyboard overlay. NIRAD ELECTRONICS
959 East 460 So., Provo, UT 84601
ZX81 Assembler,Disassembler & Debug
on cassette. $15. Info, send SASE.
B Berch 19 Jaques St Roch. NY 14620
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 right 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 $2.00 per program we
use. This payment gives us the nonexclusive right to use that program in any form,
world-wide. This means you can still use it, sell it, or give it away, and so can we.
We will consider submissions of news and hardware or software reviews. Please
keep articles short (350-400 words). Again, we reserve the right to edit accepted
articles to a suitable length. We will pay 7 cents per 6 characters, including spaces
and punctuation, for accepted articles.
When you send in programs for possible publication in SYNTAX, please
include the following information:
• How to operate the program, including what to input if it does not contain
prompts.
• Whether you can run the program over again and how.
• How to exit the program.
• The Syntactic Sum (program published in Feb. 81 and Jun. 81; send SASE
for a free copy).
• What RAM size program requires.
• What ROM program uses.
We pay for this explanatory text at the same rate as for articles in addition to
payment for the program itself.
If you want us to return your original program listing or article, please include
a self-addressed, stamped envelope. Otherwise, we cannot return submitted material.
ACTION GAMES FOR ZX81 on cassette :
ZAP, BOMBS AWAY, REAL TIME LANDER,
GOLF, more 2K for 10$. Ck or MO to
Brown, 53 Cliff La., Lev. NY 11756
PICKLE MAN for IK ZX81! Eat dots &
avoid Pickle Monster!! Listing $2
w/SASE. Panero Software 3309 Lewis,
Long Beach, Ca. 90807. Challenging!
DIRECT FROM THE AUTHOR-AIR MAIL
Understanding Your ZX81 ROM $18
Sinclair ROM Disassembly Part A $15
Sinclair ROM disassembly Part B $17
U.S. Personal Cheques/money order
accepted
Ian Logan, 24,Nurses Lane,
Skellingthorpe, Lincoln LN6 OTT,UK.
Is it THE END of the world? Survive
an attack. Game of intercontinental
war. Tape $7.95. Free cat. JL Brown
Rt.#3 Box 275-J Kingston, Tn. 37763
BUFFERED BUSS/DEVELOPMENT BOARD for
ZX80/81: $34=BARE BOARD+ZX conectri
manual. $63=KIT. Includes RAM plan.
See ad in Sync. UHF MODULATOR $15 :
clean TV display,fits on ZX81. Full
line of connector hdwr: Ribbon to
ZX,$5. Send stamp for info. Prompt
ship. COMPUTER CONTINUUM, 301-16 AV
San Francisco CA 9411g. 415 7526294
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_i_)_Evening Phone_(_)_
ZX8183
I own a □ Sinclair ZX80 □ Sinclair ZX81 Telephone orders call
617-456-3661
23
*10 FREE ZX-81 Programs 10 FREE*
Games & home fin. Send $1.50 Pst
& Hndl. -BUDGET CMPT. CLUB ,1311
N. Ode St. 621#,Rosslyn,VA,22209
ZX81/lk Listings: BLACKBOX-OTHER
VERSIONS USE 8K! MASTERMIND & BIO¬
RHYTHM also included. $5 & SASE To
G.Haroney, 106-B Antoinette Ct.
Charlottesville VA. 22903
PUT THAT ZX81 TO WORKM
SORT -A great collating tool which
files 1000s of items in up to 29
categories on just 1KI $3 gets you
list/explanation to learn build on.
LEARN DATA HANDLING -ZX81 Phone Book
16K-Holds 720 names! Makes a very
useful cataloging device for other
items too. Fully editable. Send $4
for list w/detailed explanation.
Tom Woods Box 64 Jefferson,NH 03583
HOT Z lets you read and write Z80
and floating-point machine codes.
Available for 16K ZX80,81 and in a
hi-mem version for 32K+. $19.95,
cassette with full documentation.
Sinware, Box 323, Dixon, NM 87527
ADVANCED SOFTWARE FOR 16K ZX81's!!!
ZX-FORTH,ZX-CALC(Spreadsheet), ZX-
FILE, ZX-BUDGET, ZX-PLAN(Personal
Calendar), ZX-INVENTORY. $20 ea. or
3 for $50 or all for $100. SofTek,
Box 4232, Santa Fe, NM 87502-4232.
THE
H\RV\RD
GROLP
Bolton Road, Harvard, Mass. 01451
*** ASTROLOGY-learn to write a pro¬
fessional horoscope.Analyse person¬
alities & mate compatabaility.2 pro¬
grams available.Both list planets &
houses.One then prints an analysis,
the other,a chartwheel,suitable for
professional use. Astrology trainer
included. Tape $ 16. (914)255-5521.
L&S,POB 935 NewPaltz NY 12561, 16 K
FREE SOFTWARE CATALOG for the
collector.ZX80/l/M.Ace 8KROM/16KRAM
Send a SASE today. M.C.Hoffman
P.O. Box 117, Oakland, N.J. 07436
***********************************
*ZX-81, lk, 16k, games, utilities,*
*business programs. Send for your *
*$1.50 catalog today and receive *
*a free game. OMEGA ENTERPRISES, *
*P.O. BOX 1802, Indep., MO 64055 *
***********************************
ZX-81/lK-Listing 6 Games-$2
Z-Games POBox 367 Ringoes, NJ 08551
Cassette I/O for ZX81 : This set of
utility routines makes it possible
for the user's program to selective¬
ly read or write strings and arrays
to a cassette. That data may then
be read by the same program or dif¬
ferent programs.The routines occupy
approx 500 bytes and require 2K or
more RAM. « $20/Cassette. COSMONICS
Box 10358, San Jose, CA. 95157.
First Class
U.S Postage
PAID
Harvard, MA
Permit No. 8
01451
