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Sequential Access Files

 
In sequential files, each data item is stored immediately following the previous one. The data in the file is stored in the order that it is produced. The data is read in the same order that it is stored. You read a sequential file from beginning to end. This results in a compact data storage structure and ease of programming.
The following example uses three files with sequential organization. The first two contain sorted data. They are merged to create the third file. Merging two files lends itself well to sequential organization.
 
10    REM Merge two sorted files
20    CREATE ASCII "merged",10
30    ASSIGN @F1 TO "file1";FORMAT ON
40    ASSIGN @F2 TO "file2";FORMAT ON
50    ASSIGN @M TO "merged";FORMAT ON
60    DIM Key1$[80],Key2$[80]
70    ON END @F1 GOTO Endf1
80    ON END @F2 GOTO Endf2
90    ENTER @F1;Key1$
100   ENTER @F2;Key2$
110   LOOP
120     IF Key1$>Key2$ THEN
130       OUTPUT @M;Key2$
140       ENTER @F2;Key2$
150     ELSE
160       OUTPUT @M;Key1$
170       ENTER @F1;Key1$
180     END IF
190   END LOOP
200 Endf1:! only file2 has any more data
210   ON END @F2 GOTO Alldone
220   LOOP
230     OUTPUT @M;Key2$
240     ENTER @F2;Key2$
250   END LOOP
260 Endf2:! only file1 has any more data
270   ON END @F1 GOTO Alldone
280   LOOP
290     OUTPUT @M;Key1$
300     ENTER @F1;Key1$
310   END LOOP
320 Alldone:! both files are out of data
330   ASSIGN @F1 TO *
340   ASSIGN @F2 TO *
350   ASSIGN @M TO *
360   END