BUG: VB for MS-DOS Changes Basic PDS 7.0 STRINGs to LONGs (101664)

SYMPTOMS

Loading a file into Visual Basic version 1.0 for MS-DOS causes "Type Mismatch" or "Illegal Function Call" and possibly other compile-time and run-time errors if the file was originally saved in Microsoft Basic Professional Development System (PDS) version 7.0 binary format.

This problem does not occur in Basic PDS version 7.1 and only occurs when transferring binary format files from PDS version 7.0 to Visual Basic version 1.0 for MS-DOS.

CAUSE

Files saved with the binary format from Basic PDS version 7.0 can be loaded into Visual Basic version 1.0 for MS-DOS, but Function or Sub procedure parameters that have the type STRING specification character (for example, MyString(A$)) are incorrectly converted to a type LONG (for example, MyString(A#)) when loaded into Visual Basic version 1.0 for MS-DOS. This is also true for functions defined to return the STRING type; for example, Function A$() becomes Function A#().

This problem does not occur when moving files from Basic PDS version 7.10 or Microsoft QuickBasic programs to Visual Basic for MS-DOS.

MORE INFORMATION

The Microsoft Basic Professional Development System (PDS) version 7.0 supports a Binary Fast Load and Save format option under the FILE : SAVE and FILE : SAVE AS menu options. When upgrading from PDS version 7.00 to Microsoft Visual Basic version 1.0 for MS-DOS, programs that had been saved with the Binary Fast Load and Save format option cause an incorrect change in the type for string parameters and functions defined to return a string if either is declared using the STRING type specification ($).

When saving a file from Microsoft Basic products (the Microsoft QuickBasic series, Basic PDS, and Visual Basic for MS-DOS), you can choose to from two save formats -- text and binary. The files you save with the binary format are actually partially compiled code. They are faster to load because they have already been through the first phase of parsing.

Steps To Reproduce Problem

In Basic PDS version 7.0, type in the following code:

   DECLARE FUNCTION myfunction! (a$)
   DECLARE FUNCTION mystringfunction$ ()

   FUNCTION myfunction! (a$)
   END FUNCTION

   FUNCTION mystringfunction$()
   END FUNCTION

   SUB mysub(b$)
   END SUB

Save the file in Binary - Fast Load and Save format. From the File menu, choose Save As. Type in a file name, and select the 'Binary - Fast Load and Save' format option
Exit from Basic PDS version 7.0.
Start Visual Basic version 1.0 for MS-DOS, and load the file saved in step 2.

The code appears as follows:

   DECLARE FUNCTION myfunction! (a#)
   DECLARE FUNCTION mystringfunction# ()

   FUNCTION myfunction (a#)
   END FUNCTION

   FUNCTION mystringfunction#()
   END FUNCTION

   SUB mysub(b#)
   END SUB

Note that all STRING type specification characters ($) have been changed to LONG type specification characters (#).