SYNTAX ZX80’ A PUBLICATION OF THE HARVARD GROUP VOL. 2 NO. 4 ISSN 0273-2696 APR., 1981 SINCLAIR 8K ROM SOFTWARE Sinclair now offers cassette programs for the ZX80 and ZX81 (story p.2) with 8K ROM. These tapes include education, games, and business and home programs. Two more tapes, Junior Education (IK RAM) and Z80 Assembler (16K RAM) , for writing Z80 machine code, will be ready by April. Also available in April or May will be a Learning Lab from Sinclair for the ZX81 and Language Learning, a set of programs to teach modern languages . Sinclair will send a catalog of 8K ROM software with each delivered 8K ROM and tapes will be available in the US. Sinclair has no plans to produce software for the 4K ROM. 8K ROM PRINTER COMMANDS: LLIST — Lists to printer instead of screen, LPRINT- -Directs output to printer instead of screen, COPY-- Outputs screen display to printer. CLASSIFIED ADS IN SYNTAX Now you can buy, sell or swap plans, software or hardware with other ZX80 and MicroAce owners with SYNTAX classified ads. Reach hundreds of readers for only $2.75 per line (minimum 4 lines) . Send your ad copy, typed 35 characters per line, to Classified Ads, SYNTAX ZX80, RD2 Box 457, Bolton Rd, Harvard, MA, 01451. Please include a check with your copy. No credit card or telephone orders . We need your ad by the 15th of any month to appear in the next month's issue. Include your name and address in each ad. NEW PRODUCT UPDATES Latest on Sinclair's new ROMs and RAMs --both are in production and distribution in the UK and Sinclair US expects to receive units shortly. However, Nigel Searle of Sinclair can make no promises, and says that- owners are receiving their ROMs and RAMs in the same order thay bought their computers. Thus North American owners must wait until the European demand is satisfied. Sinclair's 32 Column printer, using aluminized paper, will be available in the UK in June. North American customers can expect to wait until some time after that to order. The printer will work with both the ZX80 with 8K ROM and the new ZX81, and will work with the 16K RAM pack. No word on other previously announced products still awaiting RAMs or ROMs. MicroPeripheral Corp. is still working on their modem design. BACK ISSUES AVAILABLE Volume 1 of SYNTAX, consisting of the November and December issues , is being reprinted as a single combined issue. New subscribers can order the Nov/Dec issue for only $5.00. Send your name, address and check for $5.00 or credit card number with expiration date to SYNTAX, RD 2 Box 457, Harvard, MA, 01451. We also have limited numbers of the January, February, and March issues left, available for $4.00 each. Catch up on all the stories. 1 SINCLAIR ANNOUNCES ZX81 COMPUTER Sinclair Research unveiled a new computer at a press conference in England in mid-March. The ZX81 comes with the same 8K ROM that will be available for ZX80s and IK RAM and sells for 307 o less than the original ZX80 . Sinclair does not plan any export sales so far, and has not submitted the ZX81 for FCC approval in the US. The new machine is smaller than the ZX80 , measuring 6 , 3x6 , 8 xl . 5 inches . It operates in 2 software-selectable modes, fast and slow. Fast is 4 times the speed of slow, and according to Sinclair, compares favorably with other personal computers. The slow mode permits continuous display even while calculating. Sinclair replaced 17 TTL chips with a custom-built chip and included only 1 RAM chip, so the ZX81 has only 4 chips altogether. The ZX81 will also be available in the UK in kit form for about $100 US. USING 8K ROM, 16K RAM ON MICROACES According to Andy Fisher of MicroAce, Sinclair's 8K ROM and 16K RAM pack are completely compatible with MicroAce machines with minor modifications. Andy's instructions : For 8K ROM: Your MicroAce kit has 2 track cuts on board (both sides of pin 21 of ROM chip) and you made 2 links on the board. Before installing the new ROM, repair the cuts using a small piece of wire and remove both links . Cut the track going to pin 13 (data line 3) and the one going to pin 14 (data line 4) of the old ROM. With a small piece of wire, make a link between the sockets of pin 13 of the ROM chip (on the PCB) and pin 18 of U6. Also link pin 14 of the Rom chip and pin 3 of U6. Now plug the new ROM chip into its socket and apply power. For 16K RAM: If you have a IK MicroAce, the 16K RAM plugs in with no changes . If you have a 2K model, remove the extra IK along with U17 . Be sure that the 2 . 2K resistor in the place of R16 is installed! Now plug in the 16K module . MicroAce Owners--Sinclair ' s owner's manual is available by mail from Sinclair Research, 1 Sinclair Plaza, Nashua, NH, 03061, or Image Computer Products . 615 Academy Dr. , Northbrook, IL, 60062, for $5,95, OUR POLICY ON CONTRIBUTED MATERIAL SYNTAX ZX80 invites you to express opinions related to the ZX80 and the newsletter. We will print, as space allows, letters discussing items of general interest. Of course, we reserve the right to edit letters to a suitable length and to refuse publication of any material. We welcome program listings for all levels of expertise. Programs can be for any fun or useful purpose. We will test run each one before publishing it, but we will not debug programs; please send only workable listings. In return for your listing, we will pay you a token fee of $2.00 per program we use. This payment gives us the nonexclusive right to use that program in any form, world-wide. This means you can still use it, sell it, or give it away, and so can wel We will consider submissions of news and hardware or software reviews. Please keep articles short (350-400 words). Again, we reserve the right to edit accepted articles to a suitable length. We will pay 7 cents per 6 characters, including spaces and punctuation, for accepted articles. When you send in programs for possible publication in SYNTAX, please include the following information: • How to operate the program, including what to input if it does not contain prompts. • Whether you can run the program over again and how. • How to exit the program. • The Syntactic Sum (using the Syntactic Sum program in the February, 1981 , issue). • Whether it fits in 1 K or 2K RAM (or 16K when available). 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. SYNTAX ZX80 * published monthly by Syntax ZX80, Inc., a wholly-owned subsidiary of The Harvard Group, RD 2, Box 457, Bolton Road, Harvard, MA 01451. Telephone 617 / 456-3661. Subscriptions: 12 issues, $25. Single issues, $4. Publisher: Kirtland H. Olson Editor: Ann L. Zevnik Associate Editor: Susan G. Barber Technical consultant: Eric K. Olson Printed by Joseph E. Marhefka, Jr., Clinton Offset Printers Clinton, MA 01510. © Syntax ZX80, Inc., 1981. All rights reserved. Photocopying prohibited. ISSN 0273-2696 2 HOG HEAVEN— ROM ENTRY POINTS first and last byte locations and the module length, also in hex. For our readers , SYNTAX ZX60 To convert to decimal , see our obtained this complete list of Mar. 81 story on number systems, global subroutine calls for the 4K In later issues we plan to ROM's eight software modules. publish detailed descriptions of Mapped here you will find the some subroutines and we expect to name and absolute hex address for offer readers the opportunity to each global subroutine. We show obtain the annotated ROM listing. BASIC 10 EDIT FIRST 0000 FIRST 013C FIRST 0256 LENGTH 013C LENGTH 011A LENGTH 03B4 LAST 013B LAST 0255 LAST 0609 IGN SP 00 LA DISP 013F K LIST 0256 NXT IS 0020 SAVE 01B6 INIT 0261 N EXPR 0025 LOAD 0206 NEWLIN 0283 P EXPR 0049 DONE 02F7 NEXTCH 0052 DELSYM 036C NC HL 0055 BLEEP 03A7 KB TAB 006C WR DIG 054C TOKENS 00BA PUTDIG 0556 PUT CH 0559 SENDCH 0560 PUTSYM 0584 SYMTXT 05A8 FILLDF 05C2 INSERT 05D5 REMGSZ 05DF LIST SYNTAX IDENT FIRST 060A FIRST 0752 FIRST 0AAD LENGTH 0148 LENGTH 035B LENGTH 0272 LAST 0751 LAST 0AAC LAST 0B1E FIND L 060A SYNTAX 07BE IDENT 0AAD CP B(J 06 1C SYNERR 08AE FIND V 0B3B RECLEN 0624 CHK SZ 09 4F LET 0C3D DEL V 065B CHK L 0958 DIM 0CD3 DELREC 0666 LE05 09E1 LCU2 0CF3 NUMBER 0679 X TEMP 0D0A PUT BC 06A1 ALPHA? 0D14 PUT LN 06BF ALNUM? 0D18 SET SP 06E0 OPNS USR 06F0 FIRST 0D1F PRINT 06F1 LENGTH 00E1 WR NL 07 IB LAST 0DFF WR TAB 0727 OPNTAB 0D1F CLS 0747 MUL 0D55 OPN09 0DCD ABS 0DF2 ROM contents copyright Sinclair Research, Ltd, , CH_SET 1980. Reprinted by permission. Both, Sinclair FIRST 0E00 and SYNTAX ZX80 own copyright interests in LENGTH 0200 this material. Photocopying prohibited, LAST 0FFF 3 HARDWARE NOTES ► Ed Haasch of Greenfield, MI, suggests that you use a DIP header in place of U17 and not remove R16 to connect expanded RAM to your MicroAce. (see "Build Additional RAM" Mar, 81.) By leaving R16 in place, you can use your original 2K by plugging IJ 17 h ack in. Pins 2 & 4 carry the RA M s ignal. Pin 3 is C&l & pin 6 is CS2 . To use a Radio Shack 40-pin connector to connect additional RAM, run a j tamper from data line 7' (pin IT) to pin 23 B in stead of using that space for RAM. (But see the ZX81 pinout following.) We got some surplus 100-pin connectors and cut 46-contact sections from them (23 top and 23 bottom contacts to fit the ZX80 bus). Two hints: First, use a hacksaw blade made for cutting hard materials --the housings are glass-filled. Also, cut on an extra contact point and sand the housing down to size to avoid removing insulation next to the end contact. ►Sinclair’s new ZX81 uses all the edge connector pins with minor changes. Pin 23B is no w used for ROM CS, pin 2T becom es RAM CS, and pin 12T becomes NAY, Because Sinclair's printer is compatible with both designs, you -may want to remember their pin assignments when you assign pins for your designs . ►Some video monitors need external sync signals instead of composite video. For these devices, you must supply vertical and horizontal sync pulses to separate terminals. You can pick up the vertical sync pulses at IC11 (U22) pin 12 for negative-going pulses or pin 10 for positive pulses. Pick up combined horizontal and vertical sync pulses at IC19 % (U13) pin 5 for negative signals or pin 6 for positive signals. Video output appears at pin 4 "A SIMPLE SOLUTION TO A COMMON PROBLEM" ANNOUNCING KEYBOARD for the ZX 80 This low power CMOS circuit ends data entry problems common to Sinclai r-style keyboards by beeping when a key is depressed. Assembled and fits in the case. send $12°° to BURNETT ELECTRONICS 908 MORRIS ST. CINCINNATI OHIO 45206 4 4 ► 4 4 4 ' ( of IC 20 (U18) after the reversing switch. Composite video appears at the junction of R30 and R32, ►Mike Neidich of Syosset, NY, suggests adding a reset switch to avoid having to pull the power plug after every crash. Connect a normally open, momentary contact pushbutton across CIO (C2 in a MicroAce) . Mike says the best attachment points are at the- left end of R4 and the modulator's zero-volt lead. Drill the rear of the case to mount the button. ►Use your cassette's built-in loudspeaker for monitoring while loading. Ted Millen, Don Mills, Ontario, gives these instructions. On the earphone jack, find the two solder points that short together when the jack is removed. Solder a quarter-watt, 100 Ohm resistor across these terminals to feed the speaker when the computer plug is inserted. This technique provides ample monitoring volume and does not affect the computer feed. 4 SOFTSYNC SOFTWARE Softsync, Inc. , offers ZX80 Invasion, a Space- Invaders -like game. Softsync says it uses IK RAM. ($14.95 + $1.50 shipping.) Softsync, Inc. , PO Box 480, Murray Hill Sta., New York, NY, 10156. BAR GRAPHICS This program, written for a 2K MicroAce, draws bar charts on a white background with dark defined lines and a graphpaper-like effect behind the bars. It will choose 10 (0 to 10) random numbers to graph, or you can select them. Line 110 & 120 use SHIFT A; Lines 121, 122 & 133 use SHIFT S. Joe Chaiet, New Paltz, NY Note: This program won't fit in IK unless you delete some lines and improve the IF-THEN sequence efficiency. Any takers?--AZ 1 DIM U(50) 2 LET T=0 3 RANDOMISE 4 PRINT "DO YOU WANT A RANDOM GRAPH OR" 5 PRINT 6 PRINT "DO YOU WANT TO ENTER 10 NUMBERS?" 7 PRINT 8 PRINT "SELECT (1 OR 2)" 10 INPUT Z 11 IF Z>1 THEN GO TO 19 15 FOR X=1 TO 10 16 LET U(X)=RND(10) 17 NEXT X 18 GO TO 60 19 CLS 20 PRINT " THIS PROGRAM WILL P RINT A GRAPH" 21 PRINT "OF 10 NUMBERS FROM 0 TO 10" 23 PRINT 25 PRINT "ENTER" 30 FOR X=1 TO 10 40 PRINT "NUMBER ";X; 45 INPUT U(X) 46 PRINT "?"; UCX) 50 NEXT X 60 CLS 65 FOR X=1 TO 32 68 PRINT CHR$ (128) ; 70 NEXT X 72 PRINT 75 LET X=*ll 80 FOR W=1 TO 10 90 LET X=X-1 91 PRINT CHR$ 0-28) ; 92 PRINT CHR$ (X+28+128) ; CHR $ (2 ) ; 105 LET T=T+1 107 IF T>1 THEN PRINT CHR$(128); CHR$ (128) ; CHR$ (2) ; 109 FOR Y^l TO 10 110 IF U(Y)>X THEN PRINT 'W; 120 IF U(Y)=X THEN PRINT "Ml"; 121 IF Y=10 AND T=1 AND U(Y)<X THEN PRINT ' W' • 122 IF Y=10 AND T=1 AND U(Y)<X THEN GO TO 140 125 IF T=1 AND UCY)<X THEN PRIN T 'WW"; 126 IF T=1 AND U(Y)<X THEN GO T 0 140 130 IF U (Y) <X THEN PRINT CHR$(1 28) ; CHR$ (128) : 133 IF ?<10 AND T=1 THEN PRINT ' V ” ; 134 IF Y 10 AND T 1 THEN PRINT CHR$(128) ; 140 NEXT Y 150 PRINT 155 IF T< 2 THEN GO TO 98 156 LET T=0 160 NEXT W 163 PRINT CHR$C128) ;CHR$C128) ; CHR$ (133) ; 165 FOR X=1 TO 29 166 PRINT CHR$ ( 3 ) ; 167 NEXT X 168 PRINT CHR$C128) ;chR$C128) ; 170 FOR X=1 TO 10 175 IF X=10 THEN PRINT CHR$(12 8) ;CHR$(U(X)+128+28) ;CHR$(128) 179 IF X=10 THEN GO TO 190 180 PRINT CHR$ (128) ; 181 PRINT CHR$ (U (X) +12 8+2 8) ; CHR $(128) 190 NEXT X 191 STOP SYNTACTIC SUM= 21956 5 DEAR EDITOR I found a way to eliminate distracting interference patterns, requiring only patience and lots of tin foil. Just wrap the TV adaptor and antenna terminals with the foil. If done neatly with no punctures , the shield covers both adaptor and antenna terminals. For complete shielding, insert the adaptor into the TV and completely cover the sides of the TV, being careful not to ground anything with the foil. This plan uses Gauss's law--no electrical field exists within hollow spherical conductors , Joseph Mariconda, Toronto, Ontario You can save several bytes in REM or PRINT statements by using single-key keywords where possible instead of entering words letter by letter. For example, to remind- yourself to write down some data, you might have a line : 100 PRINT "STOP THEN INPUT X,Y,Z" Letter by letter, the whole line consumes 27 bytes. But if after the line number you hit I for INPUT, SHIFT 5 to move the cursor left, Shift 3 for THEN, SHIFT 5, S for STOP, SHIFT 5, 0 for PRINT, SHIFT Y for ", SHIFT 8 3 times to move cursor past INPUT, and finish out X,Y,Z" you can cons tune only 14 bytes, a savings of 1/2. When you have only IK of user memory, every byte helps. Rolf L. Miller, Ventura, CA I adapted the memory test program in the Additional RAM story last month (p.3) to work in my IK ZX80 . I changed line 10 to : 10 FOR 1=152 TO 987 This program runs successfully. But when I change line 10 to : 10 FOR 1=152 TO 988 I get error code 9/80 but it prints error at 17372 twice. This indicates that the memory address at 17372 is unavailable. If I change the high number in line 10, it prints error messages for all addresses from 17372 to 17403. In a previous issue of SYNTAX, you said the largest available address was 17408. This seems to be a loss of 36 bytes. What gives? John A. Sampson, College Point, NY As you saw, the program in the March issue ended at 8000, not 8192 (8x1024, or the new total bytes available with the 8K RAM) . Your machine keeps a variable length reminder file, or stack, at the top (high addresses; of total memory. By checking only up to 16384+8000, we avoided the stack area, simplified the test program and got a memory check adequate for our purposes . You POKEd high addresses in your IK RAM; the computer used (and changed) them before you PEEKed at the contents . So it didn't see what you POKEd and gave an error. Every time your computer powers up or executes NEW, it checks to see how much memory is connected. Use this machine code program, courtesy of Sinclair, to see the number of bytes found: 1 POKE 17000,33 2 POKE 17001,11 3 POKE 17002,0 4 POKE 17003,57 5 POKE 17004,201 6 PRINT USR(17000) -16383 On IK machines, the answer will be 1024, or 2048 on 2K machines . --AZ I was using a 19" color TV as a monitor with my MicroAce and absent-mindedly touched the screen and the keyboard at the same time, ZZZAP!! The static discharged through my body into 'the keyboard and the Ull buffer. It died on the spot. A local distributor told me that the NSC 74LS365 did not have input diode protection, 6 although other brands do. Because this chip is required, users should be careful when operating near a TV screen and in the dry winter months. Static charge can definitely cause damage to the expensive MOS circuits (the Z80A & ROM) and the keyboard buffer. Mike Neidich, Syosset, NY To avoid static problems, don’t touch both your TV screen and computer at the same time. Don’t wear wool clothes, or other fibers that generate static. Discharge static in your body before touching the computer by touching a metal object (you’ll get a small shock) , especially if the room is carpeted. --AZ After I assembled my MicroAce kit and inserted the recommended jumpers, it worked perfectly for about a week. Then the cursor motion in 3 directions, quotation marks and opening parenthesis became erratic and stopped working altogether. With nothing but blind instinct to guide me, I found that tying the positive end of diode 5 to ground through a . 68 Meg resistor solved the problem. Steve Martinez, Albuquerque, NM These readers would like to contact others in their areas . If you want to hear from readers in your area, send us your name, address and phone number. We’ll publish your request when space permits--AZ *Marshall G. Olsen, 2030 Larrabee St. , Chicago, IL, 60614 *Mario Stocco, 144 Lucan St. , Apt. 105, Waterloo, Ontario, N2S 1W7 CHCJT or CLASSICS FOUR CLASSIC COMPUTER GAMES FOR THE ZX80 AND MICROACE. LUNAR LANDER MINDMASTER K-TREK LIFE PLAY LIFE, A MACHINE -LANGUAGE ROUTINE LETS YOU GROW 1000 GENERATIONS /MINUTE. PLAY K-TREK, THE STAR TREK GAME IN IK. PLAY MINDMASTER, A GRAPHIC VERSION OF MASTERMIND, WITH 9 LEVELS OF DIFFICULTY. ALL FOUR GAMES ON ONE CASSETTE, WITH GAME MANUAL, CHARTS, COLOR KEYBOARD OVERLAYS, COMPLETE LISTING IN BASIC, AND MORE! JUST POP IN THE CASSETTE AND PLAY! (REQUIRES 4K BASIC & IK MEMORY OR MORE), f 9 ’5 ALSO: OLD *1 FAMILIAR OLD PROGRAMS LIKE DICE THROW, MULTIPLICATION TABLES, AND ALSO MANY NEW, LIKE AUTO-PLOT (GRAPHS YOUR EQUATIONS, COMPLETE WITH LABELED AXES). ELECTRIC NOTEPAD LETS YOU CREATE PHONE USTS, ETC.. GAMES, PUZZLES, TEN PROGRAMS IN ALL. ALL ON ONE CASSETTE, YOUR CHANCE TO TRY OUR SOFTWARE. JUST 42.99! NO POSTAGE. NO HANDLING. NO SALES TAX. FREE! WRITE FOR OGR FREE CATALOG & RECEIVE ZX80 & MICROACE CODING SHEETS. LAMO-LEM LABS CODE 104, BOX 2382, LA JOLLA, CA 92038 & & £v6 CAI INSTRUMENTS Introduces the ‘WIDGET 1 ® Series of Peripherals for the ZX80 The ‘WIDGET ’ 0 Series oi Peripherals open the door to real computing. •WIDGET® $49.95 The Widget interlace board allows your ZX80 to communicate with the rest oi the world through both a serial KS/232 data bank and a parallel TTL input and output parts. •WIDGET* $99.95 Widgitape The Widgitape is a revolutionary tape storage system that provides the features oi high priced floppy disks at a traction oi the cost. ‘WIDGET®$99.95 Widgiprint The Widgiprinter is a 28 column thermo printer that provides a hard copy oi results irom your programs at a price you can afford. Have you developed a unique option or application for your ZX80? We at CAI would be interested in discussing the possibility oi marketing your idea for you. Contact us. Remember this new “WIDGET' Series can open the door to real computing for your ZX80. Send Check, Money Order, or Credit Card Company to: CAI Instruments, Inc. 2559 Arbutus Court Midland, Ml 48640 Or order by phone (517) 835-6145 giving your credit card number. Esa Description Unit Price Total WIDGET WIDGIPRINT WIDGITAPE J Card No. Visa ■ Mastercharge | Exp. Date j Name I Address I City State ZIP { Michigan residents add 4% sales tax 8 R.F. SHIELD Cuts down T.V. interference Kit for Micro Ace machines. Send $5.00 to: Outbound Engineering P.O. Box 218 Chandler, TX 75758 U.S.A. Why wait 2 or 3 weeks for your check to clear? Send cash. Texas residents add 5% sales tax. SOFTWARE REVIEW: CHEST OF CLASSICS BY LAMO-LEM Lamo-Lem of La Jolla, CA, offers 4 classic games on 1 cassette for $9,95, These games are Lunar Lander, K Trek, Mindmaster, and Life, The chest includes a game book giving clear directions, sample program runs, and winning strategies. Chest of Classics also includes loading instructions applicable to any cassette, game guide cards summarizing directions and commands, a custom software survey, and program coding sheets. Lunar Lander is similar to the video game of the same name. You must land your lunar module without crashing. You choose your burn time , keeping a careful eye on both velocity and fuel level. The graphics are not bad, although the lander crashes through your instrument panel during an unsuccessful try. The program 9 ignores invalid entries . (By the way, I've never beaten this game.) In K Trek you command a Klingon battle cruiser. Your mission--to destroy the Federation starships before your energy runs out. This game's graphics are OK, but the tiny display uses only 1/6 of the screen. All in all, a more fun game than the first, giving you a helmsman's console and scanner, warp drive, impulse engine, and phasor capabilities shown on a keyboard overlay. The program ignores invalid entries . Cl have yet to win this game.) Mindmaster is like the number guessing game, but uses graphics symbols instead of numbers. This version is more challenging. You choose your difficulty level (.2- 10) and deduce the correct symbols plus their order in fewer than 8 tries , The display in this game is better than the first 2. This game also has a special keyboard overlay defining only those keys needed to play. If you enter an invalid symbol , the program displays it but scores 0 points for it. Life gives you a 15x16 grid to fill with living cells in any array you choose. These colonies grow according to rules in any number of generations you choose. The Chest includes a reprint from BYTE describing the mentally stimulating potential of this game. The graphics are good; the display only uses 1/2 the screen but is large enough to see easily. Life uses machine language to efficiently store the instructions in a limited memory. Each of these programs fits easily in IK RAM, We could not load from the tape until we used a recorder with a higher volume level. Conan LaMotte of Lamo-Lem said he would record future tapes at higher volume. I was fooled the first time I tried to load these programs because no audible buzz precedes each one. We re-recorded each program on our own tapes (a good idea for valuable software) adding buzz time and now they load perfectly. Each program except Life is hard to exit; the instructions do not tell you how to do this. Try breaking while the screen is blanked. COMPUTER NUMBER SYSTEMS III In the last 2 issues we learned about hexadecimal and binary numbers, 2 systems used by computers. Now we’ll look at octal numbers. Octal, or base 8, numbers work just like binary, hex, or decimal numbers. Each digit represents a power of the base you’re working in, so an octal number is expressed as powers of 8. And as in decimal you have 10 digits and binary you have 2 , in octal you have only 8 digits, 0-7, Thus 12 in decimal stands for lxlOl plus 2x10^. In octal, 12 means 1x8^ plus 2x80, or 10 in decimal. (Remember that any number to the zero power-1.) Octal numbers are most useful for computers whose word lengths are multiples of 3 (the ZX80 word is 8 bits) . Also all old business machines , like mechanical adding machines, worked in base 8, This conversion program by Don Richardson of Hampton, VA, translates numbers to any base up to base 36. Each digit of the new number represents a power of that number, so ABCj)=AxD2+BxD1+CxD0 . To run the program, press RUN (NL) and just answer the prompts, hitting (NL) after each. Do not ask it to convert to base 1, Because base 1 has only the digit 0 , the only number you can practically represent is 0 and the computer will run interminably, 10 CLS 20 PRINT "WHAT BASE? (ENTER 10 IF YOU WANT" 30 PRINT "TO GO FROM BASE 10 T 0 ANOTHER" 40 PRINT "BASE, OR ELSE ENTER THE BASE" 50 PRINT "TO CONVERT FROM)" 60 INPUT B 70 CLS 80 IF B=10 THEN GO TO 230 90 PRINT "WHAT IS THE NUMBER?" 100 INPUT A$ 110 CLS 120 PRINT A$ ; " BASE ";B;"="; 125 LET PN=l+2* (CODE (A$) =220) 127 IF CODE (A$) =2 20 THEN LET A$ =TL$(A$) 130 LET X=0 140 LET Y=C0DE (A$ ) - 2 8 150 IF Y<B THEN GO TO 180 160 PRINT "A NON-LEGAL NUMBER 0 F BASE ’’ ; B 170 GO TO 390 180 LET X=B*XfY 190 LET A$=TL$(A$) 200 IF NOT A$=CHR$ (1) THEN GO T 0 140 210 PRINT PN*X;" BASE 10 " 220 GO TO 390 230 PRINT "WHAT BASE ARE YOU CO NVERTING TO?" 240 INPUT B 250 CLS 260 PRINT "WHAT IS THE BASE 10 NUMBER?" 270 INPUT Y 280 CLS 290 PRINT Y;" BASE 10=" ; 295 IF Y<0 THEN PRINT 297 LET Y=ABS(Y) 300 LET N=-l 310 LET N=N+1 320 IF NOT Y/B**N<B THEN GO TO 310 330 FOR 1=0 TO N 340 LET X=B**(N-I) 350 PRINT CHR$ (Y/X+28) ; 360 LET Y=Y-(Y/X)*X 370 NEXT I 380 PRINT " B'ASE ";B 390 PRINT 400 PRINT "DO YOU WANT ANOTHER CONVERSION?" 410 INPUT A$ 420 IF CODE (A$) =62 THEN GO TO 1 0 SYNTACTIC SUM=-6933 lO BEGINNER'S COLUMN- ERROR CODES AND DEBUGGING PROGRAMS One of the ZX80/MicroAce' s nicest features keeps you from entering lines with syntactic errors into a program. This saves you much time and irritation in trying to get your programs to run. But some errors in logic can get by the line checker and your program won't run, usually because you've asked the impossible or you haven't given complete enough, instructions. Remember, the computer won't know what you want unless you tell it specifically. Fortunately, the machine tells you exactly where the program screwed up. It runs the program as far as possible, then gives you an error code and the line number where the problem occurred. They appear at the bottom left of the screen as error number/ line number in a ZX80 and error number: line number on a NOW AVAILABLE keyboard . x 'conversions • Standard Computer Keyboard • Type programs in half the time • Minimize errors • Wired keyboard hooks up in minutes Plans for keyboard conversion with reverse video $ 10.00 Keyboard with complete parts and plans $65.00 Wired keyboard, complete with plans $85.00 Mail for information: L.J.H. Enterprises P.O. Box 6273, Orange, CA 92667 MicroAce. Error codes are on page 99 of a ZX80 manual and page 54 of a MicroAce manual. These error codes can be invaluable in helping you debug your program. Error code 0 means it ran with no problems. Error code 9 means it ran with no problems until it hit a STOP statement. But if you get an error code 1-8, you have trouble. Error code 1 means you set up a FOR- NEXT loop like FOR X=1 TO 10 . . . PRINT X . . . NEXT T. The computer doesn't know what NEXT T means (assuming you defined T) because X, not T, is the control variable for the FOR- NEXT loop. Make sure you use variable names consistently. Error code 2 means that you threw in a variable without defining it. Work back from the offending line and make sure that every letter variable you use has a line to define it. In the FOR- NEXT loop example above, FOR X=1 TO 10 defines the variable X, Statements like LET A=0 or INPUT A$ define A and A$. Note the difference between the variable A and the string variable A$, Defining one does not define the other although they use the same letter. The most common source of this error is just mistyping a variable name. Error code 3 occurs when you use a subscript greater than the maximum in an array you set up using a DIM statement (more on DIM statements later). For example, if your array A has 5 elements and you use A(10) , you'll get an error 3. A subscript that is an expression, like A(2*I)_. that evaluates to greater than the maximum subscript in the array also gives error 3. Error code 4 occurs with LET, INPUT, DIM or PRINT statements and means that you've overshot the limit on the number or length of variables you can use because there isn't enough memory for all 11 of them. Variable names and strings can be any length, but can use up only as much memory as you have. Your only solution is to shorten something in the memory, like the variables, screen display or program length. Error code 5 comes only from PRINT statements and means you ran out of display room on the screen. The best cure for this is just to cut the stuff you want to print. Error code 6 means the answer to a calculation has gone over 32767 or under -32768, the largest and smallest numbers the computer’s arithmetic register can handle. Just ask it to calculate a smaller number. Sometimes all you need to do is use brackets in a long calculation to make sure the running total never exceeds the limits . Error code 7 means the computer hit a RETURN statement with no corresponding GO SUB, Subroutines consist of a GO SUB statement that sends the computer to the subroutine and end with a RETURN statement to send it back to where it left. If it finds a RETURN with no GO SUB to go back to, it’s lost and stops, (See Dec., 1980 issue on subroutines.) Error code 8 occurs when you try to use INPUT as a direct command instead of as a program command. To avoid this error, only use INPUT as part of a program line. You can use most other commands directly, not as part of a program. Our trick for finding out how much memory is left is one example: typing PRINT 17408-PEEK (16400) -PEEK (16 401) *256 gives you bytes remaining and an error code 0/ — 2 . These kinds of commands give error code 0 in lines -1 or -2, but do not mean that you had an error in the line. Other direct commands , like GO TO (a line number) , do not give error codes . GO TO functions like RUN if you GO TO the first line of the program; if you GO TO a later line the computer executes the program from that line on. This can also help you find errors in your program by showing you which parts run and which don't. Try inserting marker PRINT lines , like PRINT "OK SO FAR", in the middle of calculations to see how far the computer gets before the problem occurs , This narrows the possibilities for guilty lines. The other difference between GO TO and RUN in executing a program is that RUN clears all the variables you may have already entered in the program; GO TO preserves them. 12 THE H\RVYRD GROLP Bolton Road, Harvard, Mass. 01451 First Class