VGA50()
 Switches to 50-line VGA mode.
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 Syntax

     VGA50() --> lSwitched

 Returns

     VGA50() returns .T. when the screen adapter that you use successfully
     switches to this mode.

 Description

     This function can only be used on a VGA card.  It generates a 50-line
     mode, which automatically increases CA-Clipper screen output to the
     maximum allowable coordinates.  It is therefore not necessary to also
     call the SETMAXROW() and SETMAXCOL() functions.

 Note

     Important!  This function cannot be used when windows are open.

 Example

     Switch to 50-line mode.  You can then output from line 0 to 49:

     IF ISVGA()
        VGA50()                      // Switch mode
     ENDIF

     @ 49, 10 SAY "CA-Clipper"       // Last line

     WAIT

     CGA80()                         // Return to 25 line mode