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     The _setvideomode function selects a screen mode appropriate for a
     particular hardware/display configuration. The <mode> argument can
     be one of the manifest constants shown below and defined in
     GRAPH.H.
 
     Note that in OS/2, only text video modes may be selected by
     _setvideomode.
 
                Manifest Constants for Screen Mode
 
     Mode              Type         Size        Colors      Adapter
 
     _DEFAULTMODE      Hardware default mode
     _MAXRESMODE       Highest resolution graphics mode
     _MAXCOLORMODE     Maximum colors graphics mode
     _TEXTBW40         M/T          40x25       16          CGA
     _TEXTC40          C/T          40x25       16          CGA
     _TEXTBW80         M/T          80x25       16          CGA
     _TEXTC80          C/T          80x25       16          CGA
     _MRES4COLOR       C/G          320x200     4           CGA
     _MRESNOCOLOR      M/G          320x200     4           CGA
     _HRESBW           M/G          640x200     2           CGA
     _TEXTMONO         M/T          80x25       1           MA
     _HERCMONO         Hercules     720x348     1           HGC
                       graphics
     _MRES16COLOR      C/G          320x200     16          EGA
     _HRES16COLOR      C/G          640x200     16          EGA
     _ERESNOCOLOR      M/G          640x350     1           EGA
     _ERESCOLOR        C/G          640x350     16          EGA
     _VRES2COLOR       C/G          640x480     2           VGA
     _VRES16COLOR      C/G          640x480     16          VGA
     _MRES256COLOR     C/G          320x200     256         VGA
     _ORESCOLOR        C/G          640x400     1 of 16     Olivetti
                                                            graphics
 
     Type:     M indicates monochrome. C indicates color output.
               T indicates text. G indicates graphics.
 
     Size:     For text modes, size is given in characters (column
               multiplied by rows). For graphics modes, size is given
               in pixels (horizontal multiplied by vertical).
 
     Colors:   For monochrome displays, the number of colors is the
               number of grey shades.
 
     Adapter:  Adapters are the IBM (and compatible) Monochrome Adapter
               (MDPA), Color Graphics Adapter (CGA), Enhanced Graphics
               Adapter (EGA), Video Graphics Array (VGA), Hercules-
               compatible adapter, and Olivetti-compatible adapter.
 
     Note that only standard hardware is described here, but display
     hardware that is strictly compatible with IBM, Hercules, or
     Olivetti hardware should also work as described.
 
     The two special modes _MAXRESMODE and _MAXCOLORMODE select the
     highest resolution and most colorful video mode available with the
     current hardware, respectively. These two modes fail for adapters
     that do not support graphics modes.
 
     Listed below are the video modes selected for different adapter
     and monitor combinations when _MAXRESMODE or _MAXCOLORMODE is
     specified:
 
     Adapter/Monitor     _MAXRESMODE      _MAXCOLORMODE
 
     MDPA                 fail             fail
     HGC                 _HERCMONO        _HERCMONO
     CGA color           _HRESBW          _MRES4COLOR
     CGA noncolor        _HRESBW          _MRESNOCOLOR
     OCGA                _ORESCOLOR       _MRES4COLOR
     OEGA color          _ORESCOLOR       _ERESCOLOR
     EGA color 256k      _HRES16COLOR     _HRES16COLOR
     EGA color 64k       _HRES16COLOR     _HRES16COLOR
     EGA ecd 256k        _ERESCOLOR       _ERESCOLOR
     EGA ecd 64k         _ERESCOLOR       _HRES16COLOR
     EGA mono            _ERESNOCOLOR     _ERESNOCOLOR
     MCGA                _VRES2COLOR      _MRES256COLOR
     VGA                 _VRES16COLOR     _MRES256COLOR
     OVGA                _VRES16COLOR     _MRES256COLOR
 
     Note that a color monitor is assumed for CGA adapters if the
     startup text mode was TEXTC80 or TEXTC40. If the initial text mode
     is TEXTBW80 or TEXTBW40, a noncolor CGA monitor is assumed.
 
     Hercules Support
 
     In _HERCMONO mode, only monochrome (two-color) text and graphics
     are supported. The screen resolution is 720 x 348 pixels. The text
     dimensions are 80 columns by 25 rows, with a 9 x 14 character box.
     The bottom two scan lines of the twenty-fifth row are not visible.
 
     You must install the Hercules driver MSHERC.COM before running
     your program. Type MSHERC to load the driver. This can be done
     from an AUTOEXEC.BAT file.
 
     If you have both a Hercules monochrome card and a color video
     card, you should install MSHERC.COM with the /H (/HALF) option.
     The /H option causes the driver to use one instead of two graphics
     pages. This prevents the two video cards from attempting to use
     the same memory. You do not have to use the /H option if you have
     only a Hercules card. See your Hercules hardware manuals for more
     details of compatibility.
 
     To use a mouse, you must follow special instructions for Hercules
     cards in the "Microsoft Mouse Programmer's Reference Guide". (This
     must be ordered separately; it is not supplied with either
     Microsoft C or the mouse package.)
 
     Return Value
 
     The function returns the number of text rows if the function is
     successful. If an error is encountered (that is, the mode selected
     is not supported by the current hardware configuration), the
     function returns 0.
                                    -♦-