How to Simulate Bound Executables with Basic 6.00

SUMMARY

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.

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The STUB statement adds an MS-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 MS-DOS 2.x or MS-DOS 3.x (or the MS-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 MS-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:

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;
						
```
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'
						
```
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 an MS-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.

How to Simulate Bound Executables with Basic 6.00 - 7.10 (64210)

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