1000 REM THIS ROUTINE CREATES AND ACCESSES RANDOM ACCESS FILES FOR FIXED 1001 REM LENGTH RECORDS 1002 REM 1003 REM ... COMMANDS ARE 1004 REM CMD=1 WRITE NTH RECORD 1005 REM CMD=2 READ NTH RECORD 1006 REM CMD=3 UPDATE NTH RECORD 1007 REM 1008 REM RECORD$ IS THE INPUT/OUTPUT RECORD 1009 REM N IS THE RECORD NUMBER 1010 REM INDEX IS A TWO DIMENSIONAL ARRAY DIM'ED INDEX(1,RECNUM) 1015 REM INDEX HOLDS THE NOTE VALUES FOR ALL RECORDS 1020 REM THIS ROUTINE ASSUMES LOGICAL FILE #1 HAS BEEN OPENED FOR I/O 1100 REM 1120 REM ROUTINE BEGINS AT 1200 1130 REM 1200 ON CMD GOTO 2000,3000,4000 2000 REM ............................ 2100 REM WRITE NTH RECORD 2200 NOTE #1,X,Y 2300 INDEX(SEC,N)=X:INDEX(BYTE,N)=Y 2400 ? #1;RECORD$:RETURN 3000 REM ............................ 3010 REM READ NTH RECORD 3020 REM 3030 X=INDEX(SEC,N):Y=INDEX(BYTE,N) 3040 POINT #1,X,Y 3050 INPUT #1;RECORD$ 3060 RETURN 4000 REM ............................ 4010 REM UPDATE NTH RECORD 4020 REM 4040 X=INDEX(SEC,N):Y=INDEX(BYTE,N) 4050 POINT #1,X,Y 4060 ? #1;RECORD$ 4070 RETURN
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