Q58041: INTERRUPTs Using Strings Need SSEG for Segment in QBX & BC /Fs

Article: Q58041
Product(s): See article
Version(s): 7.00
Operating System(s): MS-DOS
Keyword(s): ENDUSER | S_C H_MASM SR# S900112-133 | mspl13_basic
Last Modified: 2-FEB-1990

Because the QuickBASIC Extended (QBX.EXE) editor that comes with
Microsoft BASIC Professional Development System (PDS) Version 7.00
uses far addresses for all strings, some CALL INTERRUPT statements
that worked in earlier versions of Microsoft's BASIC products require
modification for correct results.

To correct for this behavior, change the segment passed to the
INTERRUPT to be SSEG(stringvariable).

This information applies to Microsoft QuickBASIC Extended (QBX.EXE)
and to programs compiled with BC /Fs in Microsoft BASIC PDS Version
7.00 for MS-DOS and MS OS/2.

In earlier versions of Microsoft BASIC's, near strings were used.
Because of this, the VARSEG of the string variable, or -1 in some
cases, could be used for the segment. In BASIC PDS 7.00, you must use
the SSEG function to return the segment of a string variable.

The following table shows the difference in the method of assigning
the registers for string variables:

   BASIC Versions 6.00/6.00b    BASIC PDS Version 7.00
   -------------------------    ----------------------

   inregs.DS = VARSEG(a$)       inregs.DS = SSEG(a$)   '**** SSEG
   inregs.DX = SADD(a$)         inregs.DX = SADD(a$)
   inregs.ES = -1               inregs.ES = SSEG(b$)   '**** SSEG

In addition to INTERRUPTs, the change to far strings could also have
the same effect on mixed-language programming with Microsoft C and
Microsoft Macro Assembler (MASM).

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