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_get_dos_version
================

Syntax
------

     #include <dos.h>
     
     extern unsigned short   _osmajor, _osminor;
     extern const    char  * _os_flavor;
     
     unsigned short _get_dos_version(int true_version);

Description
-----------

This function gets the host OS version and flavor.  If the argument
TRUE_VERSION is non-zero, it will return a `true' version number, which
is unaffected by possible tinkering with SETVER TSR program.  (This is
only available in DOS 5.0 or later.)

The external variables `_osmajor' and `_osminor' will always be set to
the major and minor parts of the `advertised' version number, possibly
changed by SETVER, even if TRUE_VERSION is non-zero.  You typically
need the true version when you need an intimate knowledge of the host
OS internals, like when using undocumented features.  Note that some
DOS clones (notably, DR-DOS) do not support DOS function required to
report the true DOS version; for these, the version reported might be
affected by SETVER even if TRUE_VERSION is non-zero.

The external variable `_os_flavor' will point to a string which
describes the OEM name of the host OS variety.

Return Value
------------

`_get_dos_version()' returns the version number (true version number,
if TRUE_VERSION is non-zero) as a 16-bit number: the major part of the
version in the upper 8 bits, the minor part in the lower 8 bits.  For
instance, DOS version 6.20 will be returned as 0x0614.

Example
-------

       unsigned short true_dos_version = _get_dos_version(1);
     
       if (true_dos_version < 0x0614)   /* require DOS 6.20 or later */
         puts("This program needs DOS 6.20 or later to run");
       else
         printf("You are running %s variety of DOS\n", _os_flavor);