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SEEK Statement Programming Example
 
The following program uses a combination of the SEEK function and SEEK
statement to move the file position exactly one record back and rewrite
the record if a variable is true (nonzero).
 
'*** Programming example for the SEEK function and 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
'********************************************************************
' This part of the program is an insert whose only function is to
' create a random-access file to be used by the second part of the
' program, which demonstrates the CVSMBF function
'********************************************************************
OPEN "TESTDAT2.DAT" FOR RANDOM AS #1 LEN = LEN(Rec)
CLS
RESTORE
READ NameField$, ScoreField
I = 0
DO WHILE UCASE$(NameField$) <> "END"
   I = I + 1
   RecordVar.NameField = NameField$
   RecordVar.ScoreField = ScoreField
   PUT #1, I, RecordVar
   READ NameField$, ScoreField
   IF NameField$ = "END" THEN EXIT DO
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 and print 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