110 DOPEN#1,”FILE1”,D0
120 GOSUB 290
130 RECORD#1,25
140 GOSUB 290
150 RECORD#1,25,1:GOSUB 290
160 INPUT#1,A$:GOSUB 290
170 RECORD#1,25,10:GOSUB 290
180 INPUT#1,B$:GOSUB 290
190 RECORD#1,25,30::GOSUB 290
200 INPUT#1,C$:GOSUB 290
210 DCLOSE#1
220 END
290 IF DS<20 THEN RETURN
300 PRINT DS$
310 STOP
Lines 160, 180, and 200 cause the stored values on disk to be read and stored in
A$, B$, and C$, respectively.
It is extremely useful to be able to access a record which is determined during
program operation. The following routine illustrates a procedure to query the
operator for a record number and a data and to write the data to the disk file:
100 PRINT”TYPE RECORD NUMBER AND DATA”
105 INPUT R,D$
110 DOPEN#1,”FILE1”,D0
120 GOSUB 190
130 RECORD#1,(R)
140 GOSUB 190
150 PRINT#1,D$
160 GOSUB 190
170 DCLOSE#1
180 END
190 IF DS<20 THEN RETURN
200 PRINT DS$
210 STOP
Line 130 positions the file pointer to record number (R), specified by the user.
Note that a variable used in the RECORD command must be enclosed in
parenthesis.
Line 150 causes the data stored in D$ to be stored on the disk.
The RECORD command may be omitted if the file is to be accessed sequen-
tially, which saves time during program execution. An example of this occurs
when writing a large data base to the disk file. Assume that the program has
68
To Next Page
Loading...
