Basic EGA/VGA Graphics in Protected Mode OS/2 by Calling VIO (59135)


The information in this article applies to:

  • Microsoft BASIC Compiler for MS-DOS and OS/2 6.0
  • Microsoft BASIC Compiler for MS-DOS and OS/2 6.0b
  • Microsoft Basic Professional Development System (PDS) for MS-DOS and MS OS/2 7.0
  • Microsoft Basic Professional Development System (PDS) for MS-DOS and MS OS/2 7.1
This article was previously published under Q59135

SUMMARY

It is possible to do EGA and VGA graphics in OS/2 protected mode using VIO calls for the graphics. This is done by getting the physical video buffer and modifying it (with POKE or BLOAD).

This information applies to Microsoft Basic Compiler versions 6.00 and 6.00b for MS OS/2 and to Microsoft Basic Professional Development System (PDS) version 7.00 and 7.10 for MS OS/2.

MORE INFORMATION

Basic's graphics statements (SCREEN, PSET, LINE, etc.) do not support EGA/VGA high-resolution graphics modes in OS/2 protected mode. This is because Basic writes directly to the hardware for EGA and VGA graphics. Basic directly supports CGA graphics (modes 1 and 2) in OS/2 protected mode.

For better graphics control than is provided by the BASVIO program, OS/2 Presentation Manager (PM) provides a wide range of graphics functions in the GPI (Graphics Programming Interface) calls. For information on how to program for PM using Basic, contact Microsoft Technical Support and ask for the application note "Basic OS/2 Presentation Manager Toolkit Supplement."

More Information About BASVIO

The BASVIO code example provides several different graphics routines for EGA and VGA graphics under OS/2 protected mode. Color is supported only for mode 13 (256 colors). This is because EGA color requires modifying the hardware registers. To do this, a program must have an IOPL segment.

BASVIO contains routines that allow high-resolution (EGA/VGA) graphics to be used in OS/2 protected mode in the full screen groups. These routines manipulate the physical screen buffer. This requires that the screen group be in the foreground and locked during any drawing.

Color is supported in mode 13 (320 x 200, 256 colors), but EGA color requires manipulating hardware registers. To do this, an IOPL segment is required. With some versions of the OS/2 SDK, the example program, MANDEL.C, illustrates register-based programming for EGA modes. In modes other than 13, the color parameter is a simple Boolean for setting the pixel on or off.

NOTE: Text output is not supported with these routines. Input works but is not echoed.

The following is a brief summary of the important routines provided in BASVIO: 
   Routine     Description
   -------     -----------

   VioScreen   Set the screen mode (EGA & VGA only)
   VioCLS      Clear graphics screen
   VioPSET     Set pixel
   VioLine     Draw line
   VioBox      Fill box
   VioBSAVE    BSAVE graphics screen
   VioBLOAD    BLOAD graphics screen
   DrawCircle  Draw circle outline
   FillCircle  Fill circle
NOTE: These routines cannot be used in a text window.
Modification Type:MajorLast Reviewed:12/12/2003
Keywords:KB59135
©2003 Microsoft Corporation. All rights reserved.