               Windows 3 and DOS-Extended Applications
               ---------------------------------------

              Copyright 1991 by Phar Lap Software, Inc.


    Applications produced with 286|DOS-Extender can run in the DOS
box of all three modes of Microsoft Windows 3.0 and higher. This
includes 386 Enhanced mode. 

    You can tell which the mode you are in by selecting "About
Program Manager..." from the Program Manager Help menu.


                   Windows Standard and Real Modes
                   -------------------------------

    In Windows 3 Real and Standard mode, 286|DOS-Extender can get
extended (XMS) memory from the HIMEM.SYS device driver that comes
with Windows. You will need to set the XMS memory "KB Limit" in a
Program Information File (PIF).

    You can use the Phar Lap TELLME utility to make sure that your
application is getting the extended memory it needs when running
under Windows Real and Standard modes. For example, the following
indicates that no XMS extended memory is available:

C:\>tellme -xms

-----XMS-------------------------------------------------------
XMS version.....................................2.0
Driver version..................................2.96
HMA.............................................Present
A20.............................................Off
Size of largest XMS block.......................0K bytes
Total free XMS memory...........................0K bytes

    The easiest way to make sure that your DOS-extended programs get
sufficient XMS memory in Windows Standard and Real mode is to use the
Windows PIF Editor to create a _DEFAULT.PIF file with an XMS Memory
KB Limit setting of several megabytes. Windows uses _DEFAULT.PIF if
no application-specific .PIF file is available; _DEFAULT.PIF
corresponds to a mythical program called _DEFAULT.EXE. Alteratively,
you can create a COMMAND.PIF file for the DOS box, or a .PIF file
that bears the name of your program.


                  Using PHARLAP.386 in Enhanced Mode
                  ----------------------------------

    In Enhanced mode, 286|DOS-Extender uses the DOS Protected-Mode
Interface (DPMI) services provided by Windows. You don't need to
change any .PIF file settings. 

    DOS-extended applications running under Windows 3 enhanced mode
automatically get virtual memory. 

    If you will be running 286|DOS-Extender under Windows 3.0
Enhanced mode, and do not have an 80287 or 80387 numerics coprocessor
or an 80486 processor (with built-in numerics), you will need to
install PHARLAP.386. This 32-bit virtual device driver allows
floating-point emulation to work properly under Windows 3.0 enhanced
mode. 

    PHARLAP.386 should be copied to your Windows subdirectory, and
the following line should be added to the [386enh] section of your
Windows SYSTEM.INI file:

DEVICE=PHARLAP.386

    The SYSTEM.INI file is a standard text file located in your
Windows 3.0 subdirectory.


                         Nested DOS Extenders
                         --------------------

    The DPMI server in Windows 3.0 only allows one DOS extender to be
running at a time in a given DOS "box" (virtual machine). That is,
DOS extenders cannot be "nested" under Windows 3.0 Enhanced mode. 

    For example, you cannot run 286|DOS-Extender applications from
inside the DOS shell of a DOS-extended application like Lotus 1-2-3
Release 3.1, nor can you run DOS-extended applications like 1-2-3
from within the DOS shell of a 286|DOS-Extender application. (A DOS
shell would generally be created with the C system() function.)

    If 286|DOS-Extender is started under the DOS shell of a
DOS-extended application under Windows 3.0 Enhanced mode, it will
issue an error message:

Fatal Error 286.1090: Nested DOS Extenders cannot be run in Windows 3.0
enhanced mode.

                               - END -

