@node _get_dos_version, misc
@findex _get_dos_version
@subheading Syntax

@example
#include <dos.h>

extern unsigned short   _osmajor, _osminor;
extern unsigned short   _os_trueversion;
extern const    char  * _os_flavor;

unsigned short _get_dos_version(int true_version);
@end example

@subheading Description

This function gets the host OS version and flavor.  If the argument
@var{true_version} is non-zero, it will return a @cite{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 @code{_osmajor} and @code{_osminor} will always be
set to the major and minor parts of the @cite{advertised} version number.
The external variable @code{_os_trueversion} will always be set to the
true version number.  @code{_osmajor}, @code{_osminor}
and @code{_os_trueversion} may possibly be changed by @code{SETVER},
even if @var{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 @code{SETVER} even if @var{true_version}
is non-zero.

The external variable @code{_os_flavor} will point to a string which
describes the OEM name of the host OS variety.

@subheading Return Value

@code{_get_dos_version()} returns the version number (true version number,
if @var{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.

@subheading Portability

@portability !ansi, !posix

@subheading Example

@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);
@end example