Q62773: Overflow Error OPENing ISAM File with TYPE > 255 Elements

Article: Q62773
Product(s): See article
Version(s): 7.00 7.10
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S900518-75 buglist7.00 buglist7.10 | mspl13_basic
Last Modified: 6-AUG-1990

An "Overflow" error will occur when OPENing a file FOR ISAM with a
TYPE containing a large number of elements. This number is 255 for
INTEGERs, LONGs, and fixed-length STRINGs, and 239 for DOUBLEs and
CURRENCYs. This problem occurs in both the QBX.EXE environment and
compiled EXEs.

To work around the problem, limit the number of elements in the main
type by combining some elements in a nested type or arrays.

Microsoft has confirmed this to be a problem in Microsoft BASIC
Professional Development System (PDS) versions 7.00 and 7.10 for
MS-DOS. We are researching this problem and will post new information
here as it becomes available.

Code Example
------------

The following program fragment (the majority of TYPE is left out for
space reasons) demonstrates the problem. The "Overflow" error will
occur on the OPEN statement:

TYPE BigType
  I1 AS INTEGER
  I2 AS INTEGER
  I3 AS INTEGER
                          <... I4-I250>
  I251 AS INTEGER
  I252 AS INTEGER
  I253 AS INTEGER
  I254 AS INTEGER
  I255 AS INTEGER        '255 for INTEGER/LONG/STRING*n
END TYPE                 '239 for DOUBLE/CURRENCY

OPEN "BigType" FOR ISAM BigType "BigType" AS #1  'Overflow error
                                                 'here
CLOSE

To use the workaround listed above, the TYPE BigType should be made of
nested types, such as the following:

TYPE NestType
  A AS INTEGER
  B AS INTEGER
  C AS INTEGER
  D AS INTEGER
  E AS INTEGER
END TYPE

TYPE NewBigType
  I(1 TO 250) AS INTEGER
  N AS NestType
END TYPE

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