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Q64210: How to Simulate Bound Executables with BASIC 6.00 - 7.10

Article: Q64210
Product(s): See article
Version(s): 6.00 6.00b 7.00 7.10 | 6.00 6.00b 7.00 7.10
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | SR# S900724-5 | mspl13_basic
Last Modified: 27-JUL-1990

Although Microsoft BASIC Compiler versions 6.00 and 6.00b and
Microsoft BASIC Professional Development System (PDS) versions 7.00
and 7.10 for MS-DOS and MS OS/2 can create protected and real mode
programs, they cannot create bound programs. A bound program is one
that can run both in protected mode and real mode (DOS). However,
there is a way to simulate the functionality of a bound program by
creating a real mode version of the program and then linking the
protected mode version with a module-definition file containing the
STUB statement. The procedure for doing this is described below.

This information applies to Microsoft BASIC Compiler versions 6.00 and
6.00b for MS-DOS and MS OS/2 and Microsoft BASIC PDS versions 7.00 and
7.10 for MS-DOS and MS OS/2.

The STUB statement adds a DOS versions 3.x (real mode) executable file
to the beginning of the protected mode program being created by
LINK.EXE. The syntax of the STUB statement is the following:

   STUB 'filename'

Here, filename is the name of a real mode executable file. This real
mode stub is invoked whenever the program is executed under DOS 2.x or
DOS 3.x (or the DOS compatibility box of OS/2). By default, the linker
adds its own standard stub that terminates after displaying a message
similar to the following:

   This program cannot run in DOS mode.

You can use the STUB statement to replace this standard stub with a
real mode program that exactly emulates the behavior of a protected
mode version, thus simulating a bound executable.

The following is an example of the steps necessary to do this. This
example uses the following two BASIC source files:

   REALMODE.BAS
   ------------

   PRINT "This program has the same output in protected and real modes."

   PROTMODE.BAS
   ------------

   PRINT "This program has the same output in protected and real modes."

Here are the steps:

1. Create a real mode version of the program as you normally would.
   For our example, the following two commands accomplish this:

      bc /Lr realmode.bas;
      link realmode.obj;

2. Create a module-definition file containing the STUB statement. You
   can do this with any text editor. Make sure the file is saved as an
   ASCII text file. For our example, the module-definition file
   (PROTMODE.DEF) would look like this:

      STUB 'REALMODE.EXE'

3. Create the protected mode version of the program, linking with the
   module-definition file created in Step 2. Compile the program as
   you normally would, but when linking, include the name of the
   module-definition file in the fifth link parameter. The compile
   and link commands for our example would be as follows:

      bc /Lp protmode.bas;
      link protmode.obj,,,,protmode.def;

When PROTMODE.EXE is run from a protected mode session, the following
will be the output:

   This program has the same output in protected and real modes.

When PROTMODE.EXE is run from a DOS (real mode) session, REALMODE.EXE
will be executed instead of PROTMODE.EXE. Remember that REALMODE.EXE
is appended to the beginning of PROTMODE.EXE, so it is not necessary
to have a copy of REALMODE.EXE in the current directory. The output
will be the same as if PROTMODE were run from a protected mode
session:

   This program has the same output in protected and real modes.

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