(5.9) Specific DOS Sessions

How do I boot a real version of DOS from within OS/2 Warp?

Booting a real version of DOS under OS/2 Warp provides certain features that the OS/2 Warp emulated DOS sessions cannot. For example, a specific DOS session can provide access to devices (like CD-ROM drives) and networks for which there are only DOS device drivers. A specific DOS session can also help get DOS applications which generate spurious "divide by zero" errors running again.

You may be able to run only one such session per hardware device (if that device is not under OS/2 Warp's direct control). So, for example, if you have your DOS networking software loaded in one specific DOS session, you may not start another, similar session which also accesses the same network card.

Specific DOS sessions are discussed in the online Command Reference (under VMDISK), the Master Help Index, and the printed OS/2 Warp manual. You should consult those resources first. However, if you are still unsure how to configure your system to run specific DOS sessions, follow these steps:

  1. Create a bootable DOS diskette. Insert your DOS system diskette into Drive A and reboot. When you arrive at the "A>" prompt, type FORMAT A: /S and press ENTER. (Note that you may wish to format the diskette for the smallest capacity possible, to save hard disk space later on. For example, a 5.25 inch double density -- not high density -- diskette may be formatted to just 160K by adding the /1 /N:8 parameters to the FORMAT command.) When prompted, insert a blank diskette into Drive A and press ENTER. When the FORMAT operation is complete, remove the diskette and restart OS/2 Warp.
  2. Copy FSFILTER.SYS to the diskette. Double click on OS/2 System -> Command Prompts -> OS/2 Window. Insert the diskette you just formatted into Drive A. Copy the following file to your startable diskette: \OS2\MDOS\FSFILTER.SYS.
  3. Set up CONFIG.SYS. Using a text editor (like the OS/2 System Editor) create the file A:\CONFIG.SYS with the following lines at the top:

    Change the "C:" drive letter if OS/2 Warp is installed on another drive. Add any other lines as required for your application (like CD-ROM or networking), but do not include any XMS, EMS, mouse, or memory management device drivers. Make sure that everything is referenced with a drive letter and path, as above.

  4. Set up AUTOEXEC.BAT. Likewise, create a file named A:\AUTOEXEC.BAT and make sure that the first line reads:

    changing "C:" if necessary. Add any additional lines (like PATH, SET PROMPT, and so on) as required by your application. Make sure that \OS2\MDOS is referenced in the PATH.

  5. Test your DOS diskette. Once you have configured the CONFIG.SYS and AUTOEXEC.BAT files as you wish, double click on OS/2 System -> Command Prompts -> DOS from Drive A:. A DOS session should start. Test for the functionality you need (like access to your CD-ROM reader or network). If the session is not working properly, press CTRL-ESC and shut down the session, edit CONFIG.SYS and/or AUTOEXEC.BAT as required, and repeat the test.
  6. Create the diskette image. When you are satisfied that your specific DOS session diskette functions properly, go back to the OS/2 Window and type VMDISK A: C:\DOS.IMG to create a diskette image file. (If you want the file to be located on another drive or in another directory, change "C:\" accordingly.)
  7. Create a program object for your specific DOS session. Drag a program object from your Templates folder to any target folder. When the notebook opens, enter a single asterisk (*) in the Program Name field, then click on the right arrow in the lower right. Select either DOS Window or DOS Full Screen for the session type, as desired. Click on the DOS Settings button, click OK, and scroll down until you find the DOS_STARTUP_DRIVE property. Enter C:\DOS.IMG in the field at the upper right. (If your image file is not located on Drive C in the root directory, make the necessary changes.) Change any other DOS Settings if necessary. Click on the Save button, then click on the General tab. Give your program object a name. Then close up the notebook.

You should now be able to double click on your new program object to start your specific DOS session. If you require access to your diskette drive (Drive A), use the FSACCESS command. See the online Command Reference for details.

When formatting your bootable DOS diskette, you may wish to use additional command line parameters to create a diskette with a reduced capacity. The "smaller" the diskette, the less room the diskette image file created by VMDISK will take on your hard disk. See your DOS manual for details, or use the example given above.

Related information:

(1.3) DOS and Windows Compatibility

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