Q62830: X=(-1*W)^2 Gives "Division by Zero" on 386 with 387; BASIC 7.1

Article: Q62830
Product(s): See article
Version(s): 7.00 7.10 | 7.00 7.10
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | buglist7.00 buglist7.10 | mspl13_basic
Last Modified: 6-AUG-1990

Executing the following line of code on a 80386 machine equipped with
an 80387 math coprocessor results in a "Division by zero" error:

   X = (-1 * W) ^ 2

The "Division by zero" error occurs in both the QBX.EXE environment
and within a compiled .EXE in Microsoft BASIC Professional Development
System (PDS) versions 7.00 and 7.10. The error occurs only on 80386
computers with 80387 coprocessors.

Microsoft has confirmed this to be a problem with Microsoft BASIC
Professional Development System (PDS) versions 7.00 and 7.10 for
MS-DOS and MS OS/2. We are researching this problem and will post new
information here as it becomes available. This problem does not occur
with other Microsoft BASIC products.

The following are two workarounds for the above problem:

1. Use the DOS command SET NO87=NONE to disable BASIC's use of the 387
   coprocessor. The program will then execute correctly. Note that
   disabling BASIC's use of the coprocessor usually slows program
   execution.

2. Change the line of code into two lines, using a temporary variable
   to hold the value of (-1 * W), as follows:

      TEMP = (-1 * W)
      X = TEMP ^ 2

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