May June 1980 - Commodore Computers

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42 COMPUTE. MAY/JUNE. I 198O 1980 ISSUE 4oil BIG FILES ON A BIG FILES ON A SMALL Elizabeth Deal 337 W. First Ave. Malvern, COMPUTER Pa,19355 ~a~~§5~ 337 W First Ave. The program described here demonstrates a way of reducing data storage requirements by a factor of eight. It is written in Microsoft Basic for a PET computer. I have seen several programs that create and use cross-index files mes for library search, statistical surveys and similar applications. They usually require large computers, such as a 48K system with two disk drives. . A very thorough file e handling system has been described recently by Dr. Sanger in the November, 1979, , issue of Microcomputing. In his article each attribute is coded as two letters and six attributes are permitted for each record. This T requires twelve letters and, therefore, twelve bytes. . In the method described here, each attribute is coded as yes or no and the user can have as many attributes as he desires. . If the application lends itself to such coding into a list of keys or attributes, then this system will permit the handling of large amounts off data in core at one onc time. It also permits the use of logical AND, OR or NOT operators in retrieval with any combination of attributes. By way of illustration, , a library ry search requires quick access to those entries that contain desired subject matter. Two, three, or six byte coding of each key is very core consuming, and limits the number of records that can be in core at one time. The solution I propose is twofold; : (1) set up a smart coding procedure for classification of subjects described in an article into keys that can be scored yes or no, and (2) ""pack" the data for storing it in corc, core, on tape or on disk, and then ""unpack" it, , one record at a time, during the search for the applicable attributes. This paper describes an efficient way to ""pack" and "unpack" the data so that a larger file e can be searched on a small computer without the use of accessory memory devices, such as disks. Of course, if one has a system with a disk the method described here would permit use of an even larger file. We are aware that the e first part of the solution (setting up the coding procedure) is challeng· ing. It is the real problem and the performance of the system depends on how logical and meaningful the selected keys are. Each logical record consists of the text part and the data part. The text part must be adequate for positive identification of the articles being searched, but the length should be kept to a minimum. . Name, date, and page might be enough. . The data part is what we can compress. The yes-no or 1-0 codes are entered in groups of fi fifteen fteen ones and zeros. These, in turn, , are packed into the e two byte bylC integer cgcr variable S % . variable S%. Fifteen attributes require two bytes, thirty attributes require four bytes, and so on. . A user of the system need not concern himself with what the system need not concern himself with what the program does with binary ry numbers. He only needs to know that there will be as many S% values per record as there are groups of fifteen keys. The user record as there are groups of fifteen keys. The user then needs to provide a decision for retrieving the records of interest to him. . The decision is written as a statement at the e beginning of a program and is immediately edited for syntax-type errors. and is immediately edited for syntax-type errors. Logical operators AND, , OR, NOT, , as well as arithmetic ones ( ~ , < >, < , > ) are used . The metic ones ( =, , ) are used. The decision can be written on one or more lines leading to a combining variable TR. TR is set to one if true, to a combining variable TR. TR is set to one if true, and all records meeting TR condition are then displayed. Complete instructions for writing TRT R lines are listed in lines 2970 to 3420. How is it done? For once those long tables of powers of two, that are a part of every book on programming, come in handy. The program is set up in such a way that the user thinks of the list of fifteen ftee n keys from left to right, 1 to 15. TheT program sees them as being numbered from right to left, 0 to 14. Like this: -Key numbers B%(k)k = ~ 1 233 4 5676 7 8 9 101112 11 12 13 14 15 -Program sees as m ~ 1413 12 11 10 9 8765 4 3 -Program sees as m = 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 -Input key values 100011111100000 ·Input key values 1 0 0 0 1 1 1 1 1 1 0 0 0 0 0 The program now takes key values and wherever it finds a ""1" it raises 2 to the m·th m-th power. The sum of all this is then stored in integer variable S S%(record number, , sum number)' number)*. . The bytes are used instead of at least 15. During the process of retrieval the of at least 15. During the process of retrieval the opposite procedure takes place - the sum is "un packed" into working storage of 15 values. The same packed " into working storage of 15 values. T he same values are, of course, reused by all records. The lines of the program that drive this system are 1470 to 1510 and 1920 to 1990 the other way. It seems like 1510 and 1920 to 1990 the other way. It seems like a lot of hassle, but the core saving is tremendous. The loops that do the packing and unpacking take The loops that do the packing and unpacking take from 0.2 second to 0.9 second, the latter representing all fi ftee n bits on . (These times could be reduced by all fifteen bits on. (These times could be reduced by rewriting these two loops as machine code subrou tines.) Another way to save time would be to set up tines.) Another way to save time would be to set up the most frequently used keys next to one another as this will leave the loop sooner. In the example pi ~ shown above, the program will loop ten times. Had a " 1" above, the program will loop ten times. Had a "1" been in position 4 or 11 the loop would be executed five times. The program now has two sections. One packs the data, the other unpacks it. In between, , the values should be stored on tape. And at the beginning, values should be stored on tape. And at the beginning, routines for creating and updating fil files should be provided. As listed , the program works as if it were a provided. As listed, the program works as if it were a file e system. . It can be used as a training ground in writing decision lines. It should be used as a part writing decision lines. It should be used as a part of a larger system. .
MAY/JUNE, 1980 ISSUE A COMPUTE. 43 Buy Direct From CompuMart COMPUMART NOW OFFERS THE ENTIRE DEC LSI-11 PRODUCT LINE CALL FOR PRICES & DELIVERY. Buy Direct from the Largest Commodore Dealer In the Country -— NCEI NCE/CompuMart. CompuMart. 8K-Keyboard N .... $795 16K-Keyboard B 8 ....... $995 16K-Keyboard N ....... . $995 32K-Keyboard B $1 Si ,295 32K-Keyboard K-Keyboa,d N $1.295 $1,295 B -— large keyboard igraphlcs (graphics not on keyS) keys) N -— large keyboard with graphics symbols large keyboard with graphics symbols SUPER SAVER. . Thanks to Commodore their printer prices have been drastically reduced: Commodore Printer (tractor feed) feed] ........ . wasS995 $995 NNOW 5795 $795 Commodore Printer (friction feed) wasS849 NOWS695 NEW FROM EXIDY THE SORCERER II /I 48K COMPUTER z'SO 2-80 Microprocessor. Full-Sized Full-sued keyboard keyboaid .• ROM PAC Pr09rams Programs • Mlr. Microsoft rosott BASIC .• Powerful tul Graphll:S Graphics • Sellat Serial and Parallel '10 I/O • Dual Casse1te Casselte 1/0 I/O Memory Inlernally Internally Eipandable E ~ pandatlle •· S-100 EItPanSlon Expansion Options 4BK Sorcerer II $1.395 S1.395 CENTRONICS PRINTERS The 779-2 779·2 is a tractor feed leed printer designed lor tor small business systems. Uses a 5i7 5117 do! dot mairiy matr.l lo to produce all 64 upper case clISe ASCII ASCt1 characters. Centronics Centronlu Is is the biggest name nlme in In piinlers p,lntefi and this is Is their moil mOSI popular model. modet. List. S1.245 51 . SALE! E! S1.079 51,019 The New 730-1 73G-l parallel plrallel matrix printer is Is ideally suited lor all personal p e~onal and , nd microcomputer systems. Standard Features Include: InClude: 100 cps •- BO char./line char.lllne • 3-way w ay paper handling system sy.tem •- 7x7 1.1 do! dot matrix •. 96 character ASCII t1 • List L1.t $995 S995 .. . ... SALEI SALE! SB39 5839 To meet l our Centronics' quotas we are sre ottering ollering these great specials on their r printers! printerst 753-9 3-9 9919 i 9 Data ta Processing Printer. ter. Lisl: List: 52,995 SALE! SALEt S2.395 52.395 704-9 104-9 9 i;1 9 180 CPS. List: S1.995 51,995 SALE! 51,750 51.750 701-9 101 -9 9x9 9 I 9 Matrix. Ml trlx. List: S1.595 51.595 SALE! S1.395 51,395 730-3 730·3 Serial 730. 130. List: SB95 5895 SALE! E! S745 5745 Brand New. Centronics s Model Modet137. 737. the tirsl Ur.t printer prlnter In its Its class clan capable capabte ot 01 offering oUerlng print quality qua1ily suitable lor tent tu t processing, plus the performance perl & application flexi lIedblllty required tor l or data dlta processing. p Unbelievable quality bility of ollype. type. 737-3 131-3 Serial Word Processor Printer Prinler $1,045 51 .045 737-1 737-\ Parallel Word Processor Printer 5995 The Perlect Printer for lor Small Business Bu.lnus Systems s CompuMart 2 Good reasons for buying your PET'" PET" from CompuMart: (1 (1)) $100 S100 IN FREE ACCESSORIES WITH 16K or32K PET. When Wnen you buy a 16 16Kor32KPET, K . apply 51 S100 to loward PET accessories FREE Choose Irom from the accessOries sories listed below and mdlcate indicate on your order that you have reduced the cost cosl 01 ot your accessories by (2) FREE WITH PURCHASE OF ANY PET(Offer PET{Offerextended until May 15,1980) 1980) A Texas InstrumenlS' Instruments' Hex/Octal He>/Octal Calculator (S60 Value). Value), and a set 016 ot 6 PET Vlorltbooks Workbooks (Worth 536) PET Accessories Commodore Dual Floppy Oisk Disk Olive Drive .. ... ..51,295 SI.295.00 Second Cassette- Cassette—from Irom Commodore . S95 00 Commodore PET Service Kit ...... . S30.OO S30.00 Beepcr-Tells Beeper—Tells when tape IS is loaded . S2495 Petunia- Petunia—Play Play mUSIC music Irom from PET .... S2995 S29.95 Video Buller- Buffer—Attach AttaCh another CRT .. S2995 95 Comtlo- Combo-Petunia ab
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Said the Toolkit to the Word Proces
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COMPUTE. COMPUTE. TM The Journal Fo
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Dear MICRO-ED: Dear MICRO-ED: I wou
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Look To MTU For 6502 System Expansi
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