дOCTOR вHO дATA бASE BY лEN лINDSAY тHIS DISK и WANTED TO HAVE SEVERAL PROGRAMS DEMONSTRATE FILE HANDLING, ESPECIALLY WITH RANDOM FILES. дOCTOR вHO PRESENTED ITSELF AS AN EXCELLENT TOPIC. тHIS SCIENCE FICTION SHOW HAS BEEN ON THE AIR FOR 24 YEARS NOW, WITH A TOTAL OF OVER 150 MOVIE LENGTH SHOWS. иN EACH SHOW, THE дOCTOR HAS VARYING COMPANIONS, AND MEETS DIFFERENT ADVERSARIES (AND EVEN INTERESTING MONSTERS). сO, и CREATED A DATA BASE SYSTEM THAT CAN EASILY KEEP TRACK OF A SERIES OF SHOWS. жERY LITTLE IN THIS DATA BASE IS SPECIFIC TO дOCTOR вHO (TO ILLUSTRATE THIS, WE ALSO ARE INCLUDING сTAR тREK DATA ON THE DISK). и USED 8 FIELDS OF 27 CHARACTERS EACH TO STORE THE DATA FOR A SHOW, PLUS TWO EXTRA FIELDS THAT YOU CAN DECIDE HOW TO USE. тHE TITLES FOR EACH OF THE 8 MAIN FIELDS CAN VARY DEPENDING ON WHAT INFORMATION YOU WISH TO KEEP TRACK OF. фOR THE дOCTOR вHO SHOWS и CHOSE THE FOLLOWING: сHOW нAME: дOCTOR: цOMPANION1: цOMPANION2: цOMPANION3: аDVERSARY1: аDVERSARY2: лOCATION: и'VE ALSO PROVIDED TWO EXTRA "USER" FIELDS. тHE FIRST IS AN "ид" OF 11 CHARACTERS. ыOU COULD PUT THE VIDEO TAPE NUMBER HERE, THE NAME OF YOUR FRIEND WHO HAS THIS SHOW ON TAPE, OR A SHORT COMMENT ON THE SHOW. тHE OTHER FIELD IS ONLY ONE CHARACTER. иT CAN BE USED TO RATE EACH SHOW (а,б,ц, ETC). и USE IT TO MARK THE SHOWS THAT и HAVE SEEN. сINCE и AM A TRUE дOCTOR вHO FAN, и HAVE PAINSTAKENLY ENTERED ALL THE DATA FOR THE FIRST 144 SHOWS! тHIS LARGE DATA BASE OF INFORMATION IS ON THIS DISK ALONG WITH THE DATA BASE PROGRAM ITSELF. оNCE YOU HAVE A DATA BASE FILLED WITH INFORMATION, IT IS EASY AND FUN TO USE. фOR EXAMPLE, LET'S SAY YOUR FAVORITE дOCTOR вHO ADVERSARIES WERE THE цыбермен. уSING THE DATA BASE SYSTEM, YOU CAN CHOOSE THE сEARCH OPTION, AND IT WILL LIST EVERY SHOW THAT INCLUDED CYBERMEN AS ADVERSARIES! тHE NICE THING ABOUT THIS IS THAT THE SYSTEM USES цомал'S ин OPERATOR TO FIND THE MATCHES. тHUS, YOU CAN ASK THE SYSTEM TO LOOK FOR цыб AND IT WILL FIND BOTH цыбермен AS WELL AS THEIR "PETS", THE цыберматс. рEMEMBER, THE SEARCH IS VERY PICKY ON UPPER OR LOWER CASE. тHUS, цYB WILL NOT MATCH цыб. тHEREFORE, YOU MAY WISH TO DO AS и DID ON MY DATA -- NEVER USE SHIFTED LETTERS! (оR ALWAYS CAPITALIZE THE FIRST LETTER OF EACH WORD). сINCE THIS SYSTEM USES A RANDOM FILE FOR ITS DATA, IT IS EASY TO RANDOMLY DISPLAY ANY SHOW. йUST TYPE IN THE SHOW NUMBER, AND INSTANTLY (ALMOST) ITS INFORMATION IS DISPLAYED. тO SEE THE NEXT SHOW JUST TYPE + (PLUS SIGN). тO SEE THE PREVIOUS SHOW TYPE - (MINUS SIGN). аNOTHER NICE FEATURE OF THIS SYSTEM IS бровсе. иT ALLOWS YOU TO SCAN OVER ALL THE ENTRIES, ONE AFTER ANOTHER, STARTING AFTER THE SHOW CURRENTLY DISPLAYED. иT EVEN HAS A VARIABLE PAUSE BETWEEN SHOWS. фIVE SECONDS IS THE DEFAULT, BUT FOR A FAST SCAN, USE 0 FOR THE LENGTH OF PAUSE. нотес абоут тхе програм тHE VARIABLE MARK$ IS USED TO DETERMINE WHETHER OR NOT THE INFORMATION DISPLAY IS NORMAL OR REVERSE FIELD. нEAR THE BEGINNING OF THE PROGRAM YOU WILL SEE THIS STATEMENT: DISPLAY(MARK$<> " ") дисплаы IS THE NAME OF THE PROCEDURE THAT PRINTS THE INFORMATION ABOUT THE SHOW TO THE SCREEN. иT HAS ONE NUMERIC PARAMETER. иF THE PARAMETER IS фалсе (A VALUE OF 0) THEN THE INFORMATION IS DISPLAYED NORMALLY. иF IT IS труе (A VALUE NOT EQUAL TO 0) THEN THE INFORMATION IS DISPLAYED IN REVERSE FIELD. мARK$<> " " IS A COMPARISON THAT WILL ALWAYS BE EITHER труе OR фалсе, THUS PROVIDING THE PROPER PARAMETER. нOTICE THAT TO HAVE THE REVERSE DISPLAY, EACH VALUE PRINTED MUST BE THE CORRECT LENGTH BECAUSE THE REVERSE FIELD WILL STOP AT THE LAST CHARACTER. тHE LENGTH USED IN THIS PROGRAM IS 27. тHUS, IF THE SHOW NAME IS LESS THAN 27 CHARACTERS, и HAD TO DO SOMETHING TO PRINT REVERSE FIELD SPACES AT THE END OF THE NAME. и LET цомал TAKE CARE OF THIS FOR ME BY USING SUBSTRING NOTATION WHEN INPUTING THIS DATA (FROM BOTH KEYBOARD INPUT AND FILE INPUT). фOR EXAMPLE: DIM NAME$ OF 27 INPUT "NAME:": NAME$ PRINT CHR$(18)+NAME$ PRINT "LENGTH IS";LEN(NAME$) INPUT "NAME:": NAME$(1:27) PRINT CHR$(18)+NAME$ PRINT "LENGTH IS";LEN(NAME$) рUN THAT PROGRAM AND TYPE тест AS THE NAME BOTH TIMES IT ASKS. тHE FIRST TIME IT HAS A LENGTH OF 4. тHE LAST TIME IT HAS A LENGTH OF 27 (THE VALUE WAS PADDED WITH SPACES AT THE END). пRINTING IT EACH TIME IN REVERSE FIELD SHOWS HOW THE (1:27) TAKES CARE OF FORMATTING PROBLEMS FOR ME! цALCULATING THE CORRECT RECORD LENGTH IS ALSO IMPORTANT WHEN USING RANDOM FILES. уSE THE MAXIMUM POSSIBLE LENGTH AS THE LENGTH FOR THE FILE. иN THIS CASE и HAD 8 FIELDS OF 27 CHARACTERS, 1 FIELD OF 11 CHARACTERS, AND 1 FIELD OF 1 CHARACTER. сINCE EACH FIELD IS A STRING, и ALSO MUST ADD A 2 BYTE COUNTER FOR EACH FIELD. тHUS 8*29 PLUS 13 PLUS 3 GIVES 248. тHE SMALLEST RECORD SIZE и CAN USE AND BE SURE TO HOLD ALL POSSIBLE DATA IS 248, WHICH и SET IN THE START'UP PROCEDURE. тO CALCULATE RECORD LENGTH WHEN USING врите филе REMEMBER THESE RULES: * а REAL OR INTEGER NUMBER USES 5 BYTES * а STRING NEEDS ITS MAXIMUM LENGTH плус 2 BYTES FOR A LENGTH COUNTER кNOWING HOW MANY RECORDS HAVE BEEN WRITTEN IS ALSO IMPORTANT WHEN USING RANDOM FILES. иF YOU ATTEMPT TO READ A RECORD PAST THE LAST EXISTING ONE, AN ERROR OCCURS! а COMMON WAY TO KEEP TRACK OF THE LAST RECORD NUMBER IS TO врите IT INTO THE FIRST RECORD OF THE FILE: WRITE FILE 2,1: LAST'RECORD лAST'RECORD IS A VARIABLE THAT HOLDS THE NUMBER OF THE LAST RECORD WRITTEN TO THE FILE. нOW, EACH TIME YOU USE THAT FILE, YOU CAN SIMPLY READ THE LAST RECORD NUMBER FROM THE FILE LIKE THIS: READ FILE 2,1: LAST'RECORD тHE ONLY SIDE EFFECT OF THIS IS THAT YOU CANNOT USE THE FIRST RECORD FOR REGULAR DATA. оFTEN, THIS IS NOT A PROBLEM. фOR EXAMPLE, IN OUR ORDER PROCESSING SYSTEM PROGRAMS (RUNNING UNDER ибм пц цомал) цомал тODAY SUBSCRIBERS ARE PART OF A RANDOM FILE, STORED BY THEIR SUBSCRIBER NUMBER. сINCE и USE THE FIRST RECORD TO HOLD THE LAST SUBSCRIBER'S NUMBER, и STARTED MY SUBSCRIBER COUNT WITH 2. тHUS THERE IS NO SUBSCRIBER NUMBER 1. бUT IN KEEPING TRACK OF дOCTOR вHO SHOWS, THERE IS A SHOW NUMBER 1. сINCE IT CAN'T BE WRITTEN INTO RECORD NUMBER 1, WE SIMPLY ADD 1 TO THE SHOW NUMBER TO GIVE THE RECORD NUMBER (READ THIS SENTENCE TWICE - IT MAKES SENSE). тHUS SHOW NUMBER 1 IS STORED IN RECORD NUMBER 2. бOTH READ'RECORD AND WRITE'RECORD PROCEDURES DO THE RECORD NUMBER CONVERSION. аNOTHER THING и TRY TO DO IS KEEP MY FILES CLOSED AS MUCH AS POSSIBLE. оN A цOMMODORE DISK, ALL FILES MUST BE PROPERLY CLOSED OR THEY CAN'T BE OPENED LATER. сO, и TAKE PRECAUTIONS (IN CASE OF A POWER OUTAGE ETC.) AND KEEP THE FILE CLOSED WHEN IT IS NOT DIRECTLY BEING USED. фOR EXAMPLE, WHILE SEARCHING THE FILE FOR MATCHES, и USE THE PROCEDURE READ'RECORD DIRECTLY, AND DON'T CLOSE THE FILE AFTER EACH RECORD IS READ. и ONLY CLOSE THE FILE AFTER и FIND A MATCH. хOWEVER, WHEN JUST GETTING INFORMATION ABOUT ONE SHOW, и HAVE THE PROCEDURE READ'IT WHICH FIRST OPENS THE FILE, THEN READS THE RECORD, THEN CLOSES THE FILE. тHUS THE FILE IS CLOSED WHILE и LOOK AT THAT RECORD (AND POSSIBLY EDIT IT). нOTE THAT и ALWAYS CLOSE THE FILE AFTER и WRITE TO IT. тHUS и ONLY HAVE ONE WRITE'RECORD PROCEDURE.