The following program illustrates the feature which permits access to individual
bytes within a record:
110 DOPEN#1,”FILE1”,D0
120 GOSUB 900
130 RECORD#1,25,1
140 GOSUB 900
150 PRINT#1,”FIELD 1”
160 GOSUB 900
170 RECORD#1,25,10
180 GOSUB 900
190 PRINT#1,”FIELD 2”
200 GOSUB 900
210 RECORD#1,25,30
220 GOSUB 900
230 PRINT#1,”FIELD 3”
240 GOSUB 900
250 DCLOSE#1
260 END
900 IF DS<20 THEN RETURN
910 PRINT DS$
920 STOP
Lines 130, 170, and 210 cause the file pointer to be moved to different places
within record number 25. The following illustration is a representation of the
contents of record number 25 after the above example is executed:
1 2 3 4 5
12345678901234567890123456789012345678901234567890
--------------------------------------------------
FIELD 1* FIELD 2* FIELD 3*
--------------------------------------------------
Where * represents a carriage return (CHR$(13)).
NOTE
It is important that the fields are written in order
because writing to a byte at the beginning of the
record flushes the rest of the record in memory. This
means that while it is possible to position and write
first to byte 1 and then to byte 20, it is NOT possible
to first write byte 20 and then byte 1.
Since the carriage return is recognized as a terminator by the BASIC INPUT
statement, the data may be retrieved by the following sequence:
67
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