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 Backgr ound . . . . 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 = I NT (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 COM PL

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 *Sti ck-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 Programs for either ZX80-8K or Z X 81

*PLANE FRAME-model 1 ing 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/Greenvi 1 le,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

RKyA™$99sSrial$995Wi!

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

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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 A VC 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 1 14 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 all ZX81’s, (IK memory 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!

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□ My check for $19.95 is enclosed.

Please charge my □ Mastercard □ Visa

Account Number _ _ Exp _

Signature _ _ _

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EXPANDING EXISTING 16K PROGRAMS

If you upgraded to 48K RAM for your ZX8 1 , 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 :‘r u 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 - “ypsc	a J O 1- -L.NRN
38	PRINT	fiT	S' ; I ; E: HOW	ITHNY PHY M

£ NT S P £ R V E HP T 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>4jpji 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	I F 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 —
i C? *£•	STOP
25©	f-' .9 I N f	M~ !	S , l	; : - p	v HP NT =-.' "
2&s5	INPUT	fT*
2 t'8	ij 1_. t>
k*38 (1 + 1 3	L ET M	= U-IN	1 K	2' l H -	S X 1 3 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

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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 must 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 FIN D ft REM 310 LET ft=ft+5 320 LET X=PE EK 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

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

548 IF X =118 THEM LET EOL=i 558 LET X $ --CHR $ X

580 R FT i jDM

1888 REM DONE WITH XFER 1818 LET URLUE-USR 3 ft 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 ZX8 1 doesn't hold simple decimals like .5 & .25 exactly. That is because (1/10) expands as ( 1/8 ) x ( 8/1 0 ) , 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

L ET O = P ti E K 16480 +2 5 5 *PFFK

for 204 as ex- Use Program 1 to ZX81 representa-

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=©

"ENTER ft NUMBER THftT w : hhls y j. T n h DEOIHPL POINT own CO NT ft INS 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

POKE U +5 , PEEK (U+5) +1

14-0 PRINT PEEK X;

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 arrive 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

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 Hr s : 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 QTg Qp GRAPH ICS********** 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 : Secur ity Program-protect prog¬ rams and f iles;makes*them nonlist- able or editable;must enter code to use;on cassette;send $15 to Mark E. Roger s ,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 , Calif ornia 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

EASTH ILL , OAKHAM , MAO 1 0 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*DEFECTI VES 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 ; For ays 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 Mas ter mind, 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

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 WORK M 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-ZX8 1 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 (Per sonal 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 compatabaili ty . 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