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'The following program uses the SEEK function and the SEEK statement
'to move the file position exactly one record back and rewrite the
'record if a variable is true (nonzero).  The RESTORE statement is
'used to set the data pointer to the first DATA statement.
 
CONST FALSE = 0, TRUE = NOT FALSE
'Define record fields.
TYPE TestRecord
   NameField  AS STRING * 20
   ScoreField AS SINGLE
END TYPE
 
'Define a variable of the user type.
DIM RecordVar AS TestRecord
DIM I AS LONG
 
'Note: This part of the program is an insert whose function is to
'create a random-access file to be used by the second part of the
'program, which demonstrates the SEEK function and statement.
 
OPEN "TESTDAT2.DAT" FOR RANDOM AS #1 LEN = LEN(RecordVar)
CLS
RESTORE
READ NameField$, ScoreField
I = 0
DO WHILE NameField$ <> "END"
   I = I + 1
   RecordVar.NameField = NameField$
   RecordVar.ScoreField = ScoreField
   PUT #1, I, RecordVar
   READ NameField$, ScoreField
LOOP
CLOSE #1
 
DATA "John Simmons", 100
DATA "Allie Simpson", 95
DATA "Tom Tucker", 72
DATA "Walt Wagner", 90
DATA "Mel Zucker", 92
DATA "END", 0
 
'Open the test data file.
DIM FileBuffer AS TestRecord
OPEN "TESTDAT2.DAT" FOR RANDOM AS #1 LEN = LEN(FileBuffer)
'Calculate number of records in the file.
Max = LOF(1) \ LEN(FileBuffer)
'Read contents of each record.
FOR I = 1 TO Max
   GET #1, I, FileBuffer
   IF FileBuffer.NameField = "Tom Tucker" THEN
      ReWriteFlag = TRUE
      EXIT FOR
   END IF
NEXT I
 
IF ReWriteFlag = TRUE THEN
   'Back up file by the length of the record variable that
   'is used to write to the file.
   FileBuffer.ScoreField = 100
   SEEK #1, SEEK(1) - LEN(RecordVar)
   PUT #1, , RecordVar
END IF
 
CLOSE #1
KILL "TESTDAT2.DAT"
END