(Excerpt from a message dated 08-30-99, Lee Aroner to David Noon)

Hi Lee--

LA>   I'm still searching for a coherent explaination/layout of the 
  >   Family Mode(?) API.

    Programs written using only the Family API functions could be
induced to run both in real mode under DOS and in 16-bit protected mode
under OS/2.  The best source of information on FAPI functions is the
OS/2 1.3 version of the "Control Program Programming Reference."

    There is a fairly good discussion of the underlying design and usage
of the Family API in Gordon Letwin's book "Inside OS/2" [ISBN
1-556615-117-9], Microsoft Press, 1988, pp 251-256.  (Letwin was the
Microsoft "Chief Architect" for systems software during the joint
development program.)  The FAPI Library (contained in "bound" EXE files
that could run under either system) includes DOS (INT 21h) analogs of
the equivalent OS/2 FAPI calls.  When running the program in real mode
under DOS, these "library" functions are called; when running in
protected mode under OS/2, the calls are to the equivalent 16-bit OS/2
API function DLLs.  The "decision" as to which set to enable is
established by the program loader.  As I understand it, there is no way
to switch operating modes during execution of the program.

    According to the book "Converting Applications to OS/2" by
Moskowitz, Evans, and Bergman [ISBN 0-13-171943-2], Brady Books (Simon &
Shuster), 1989: "There isn't really anything magical about the FAPI
library.  It represents the OS/2 [v 1.x] functions that Microsoft and
IBM thought would be most needed and/or used if people wanted to create
dual-mode applications."  This book presents methods for creating your
own "FAPI" library of dual-use 16-bit functions (pp 205-211), as well
procedures for porting C programs from DOS to "native" 16-bit OS/2.

    Regards,

        --Murray

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