Section 2 - Commodore Computers

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136 COMPUTEt tv1oy, 1982. Issue 24 136 COMPUTE) May. 1982. Issue 24 There are times when you will write a program that is so lmge large that it will need ev",)' every last meIlZ01)' memory cell in your com/mler, computer. This (I,rtiele article shows several ways to Teduce reduce the size of yourIJ1'0!5"a.ms, programs. In general, geneml, thl'sl' these techniques a-/JI)I), apply 10 to WI)' any computer rOIllI}//II''- using /lsillg BASIC, nol not just to the Ihe VIC-20, VIC-20. Putting The Squeeze Putting The Squeeze On Your VIC20: Getting The Most Out Of 5000 Bytes Out Of 5000 Bytes Stanley M M. Berlin Dallas,1X IX Five-thousand of almost anything seems like a lot; a Christmas bonus of $5000 would make anyone happy; 5000 jell y beans wo uld be more than even happy; 5000jelly beans would be more than even our Presidelll President could eat; 5000 days is over fourteen years. However, there are otherr circumstances when a quantity of five-thousand really is not so when a quantity of fi ve-thousa nd really is not so much, much. Five-thousand raindrops would probably go unnoticed, unnoticed. The time when five-thousand is a reallyy small quantity is when you are writing a program and have onlyy five-thousand bytes (memory locations) in which to do the job! I remember working twenty years ago with a 4000 character IBM 1401I Computer and feeling confident that if I had only another twenty-five memory locations I would be able to complete the program. program, Times have changed during the last twenty years and there are many programmers who now work with virtual memol)' memory systems. systems, [WheTe [Where the computer can use disk memory as if il it weTe were RAM -— Ed.] Ed.} where there is no such problem as being constrained by the amount of memory, memory. With technology moving as fast as it is, persons working on small microcomputers probably y will not have to wait twenty years for a virtual memory-like system. When that tilne time arrives, people will not have to write articles like this one. However, today, if you are writing programs for the <strong>Commodore</strong> VIC-20 you will have to li ve with the constraint of having only have to live with the constraint of having only 5,000 bytes worth of memory in which to do your work. Anyone who has done any serious programming Anyone who has done any serious programming for the VIC20V I knows that it does not take many BASIC statements before youu get that dreaded "OUT OF MEMORY" message. Of course, the VIC20 is nice enough to let you know when you turn it on that by the time it gets through allocating 506 bytes for the video mapping, and another 506 bytes for color mapping on the screen, and reserves memory space for such other things such as tape cassette buffers, you have onlyy 3583 bytes of memory in which to store your program. So, there you are busily entering your new BASIC program and VIC sends you the "OUT OF MEMORY" message. What are your options? You cann resign yourself to the factt that, no matter what you do, the program will never fit into memory and abandon your project. Surely, no programmer worth his or her salt would exercise this option! Another option is to run out and purchase a memory expansion unit. unil. This is not too bad a solution except, at the time this is being written, there is no such item available. Even if there were, it is surely a costly solution. The last option is to roll up your sleeves and dig into yourr program with a finely honed scalpel to perform surgery onn it. That is certainly the most challenging option, and it is the certainly the most challenging option, and it is the purpose of this articlee to pass on a few points to help you in your efforts. The items discussed will be from a BASIC programmer's point of view. Technical system information will be avoided except when it is necessary for a clear understanding of the issue. issue, Although these suggestions are aimed at the VIC20 owner and the VIC20 is the computer used to validate the data, much of the information is pertinent to other computers using Microsoft BASIC. One last point prior to moving to the meat of this article; many of the suggestions presented here are a tradeoff between good program docu here are a tradeoff between good program docu mentation and the amount of memory used. Remark (REM) statements li berall y scattered through mark (REM) statements liberally scattered through out a program provide the roadmap when you are
MENAGERIE . ... $11.95 GRAFIX MENAGERIE $11.95 Demonslrale Demonstrate whol whot your SJOO S300 mi.ode miracle can do! Two·program Two-program sel unleashes VIC's graphics. SHOWOFF contoim contains Colo. Color Koleidoscope, Arcode Arcade C.itters, Critters, Custom fonts, Fonts, Electronics Schemotic, Schematic, and Music Notation, Nalolion. PLOTTING uses u.esdol.plolond dot-plot ond line-plot ·plol roulines routines 10 to make equotions perform Compuler computer video· videoort on your you' screen. Chonge Change equotion equation values ualuel ond and creole create your/ 011 own inle.esting interesting patterns. pOllerns. Plot rout'nes routines mayy be eosily easily i included) in n your own progroms. programs. GRAFIX DESIGNER ..... $14.95 $14.9: Two·program Two-program .el let help. helps you yov de.ign design (\I"am cuitom grophiu graphic*
Page 1 and 2: 1\ MALA Educational Programs M\~ Fo
Page 3 and 4: May. 1982. Issue 24 COMPUTEI 101 Ma
Page 5 and 6: • the battle for the moons of Jup
Page 7 and 8: May, May. 1Q82lssue 1982, Issue 24
Page 9 and 10: i i ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~,
Page 11 and 12: • Announcing the Printing Breakth
Page 13 and 14: May. 1982. Issue 24 COMPUTEI 111 Ma
Page 15 and 16: APPLE • ALTOS • ATARI • MAXEL
Page 17 and 18: CBM Maintenance In-House DOWNEY, CA
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Section 2 - Commodore Computers

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