This is part of Family API which allow to create dual-os version of program runs under OS/2 and DOS

Note: This is legacy API call. It is recommended to use 32-bit equivalent

2021/09/17 04:47 · prokushev · 0 Comments
2021/08/20 03:18 · prokushev · 0 Comments


This call sets the mode of the display.


VioSetMode (ModeData, VioHandle)


  • ModeData (PVIOMODEINFO) - input : Address of the mode characteristics structure:
    • length (USHORT) : Input parameter to VioSetMode. Length specifies the length of the data structure in bytes including Length itself. The minimum structure size required is 3 bytes. OS/2 sets to the first mode (in the list of modes supported by this display configuration) with a data structure matching the mode data specified.
    • type (UCHAR): Mode characteristics bit mask:
Bit Description
7-4 Reserved, set to zero.
3 0 = VGA-compatible modes 0 thru 13H.
1 = Native mode.
2 0 = Enable color burst
1 = Disable color burst.
1 0 = Text mode.
1 = Graphics mode.
0 0 = Monochrome compatible mode.
1 = Other.
  • numcolors (UCHAR): Number of colors defined as a power of 2. This is equivalent to the number of color bits that define the color, for example:
Value Definition
0 Monochrome modes 7, 7+, and F.
1 2 colors.
2 4 colors.
4 16 colors.
8 256 colors.
  • textcols (USHORT): Number of text columns.
  • textrows (USHORT): Number of text rows.
  • pelcols (USHORT): Horizontal resolution, number of pel columns.
  • pelrows (USHORT): Vertical resolution, number of pel rows.
  • Attribute Format (UCHAR): Identifies the format of the attributes.
  • Number of Attributes (UCHAR): Identifies the number of attributes in a character cell.
  • Buffer Address (ULONG): 32-bit physical address of the physical display buffer for this mode.
  • Buffer Length (ULONG): Length of the physical display buffer for this mode.
  • Full Buffer Size (ULONG): Size of the buffer required for a full save of the physical display buffer for this mode.
  • Partial Buffer Size (ULONG): Size of the buffer required for a partial (pop-up) save of the physical display buffer for this mode.
  • Extended Data Area Address (PCH): Far address to an extended mode data structure or zero if none. The format of the extended mode data structure is determined by the device driver and is unknown to OS/2.
  • VioHandle (HVIO) - input : Reserved word of 0s.

Return Code

rc (USHORT) - return

Return code descriptions are:

  • 0 NO_ERROR


VioSetMode initializes the cursor position and type.

VioSetMode does not clear the screen. To clear the screen, use one of the VioScrollxx calls.

The disable color burst bit in the Type field in the VioSetMode data structure is functional only for the CGA and VGA. This bit causes the color portion of the video signal to be suppressed, producing a black and white mode on composite monitors attached to the CGA. On VGA, the bit causes the color lookup table to be loaded with values that produce shades of gray instead of colors, again producing a black and white mode. For all other combinations of adapters and displays, the setting of this bit is recorded and returned on any subsequent VioGetMode call, but otherwise is ignored.

For text modes in full-screen sessions, the number of rows on the screen is determined by the availability of fonts of the correct size. For any specified mode, the size of the character defined by the font must be (Horizontal Resolution)/(Text Columns) dots wide and (Vertical Resolution)/(Text Rows) dots high. For example, an 8×8 font would support 39 through 43 text rows if the screen resolution were 640×350.

If VioSetState request type 6 has been issued previously to select the target display configuration for VioSetMode, the mode is set on the display configuration selected. If that display configuration does not support the mode specified, an error is returned.

Assuming no target display configuration for VioSetMode is selected, the mode is set on the primary configuration. If the primary configuration does not support the mode specified, the mode is set on the secondary configuration.

The table below shows the VioSetMode parameters required to set all the modes supported by the CGA, EGA, VGA, and PS/2 Display Adapters. The modes native to the 8514/A and other advanced video adapters are set with the Adapter (programming) Interface to these adapters, not VioSetMode.

Note: Although graphics mode support is provided in VioSetMode, this support is not provided by the Base Video Handlers provided with OS/2.

Table 5-1. Display Mode Attributes Supported by Adapters

0544025320200[CGA/CD], CGA/Comp, [EGA/CD], [EGA/ECD], VGA/Mono, VGA/Color, VGA/Plasma
0*544025320350[EGA/ECD], VGA/Mono, VGA/Color, VGA/Plasma
0+544025360400VGA/Mono, VGA/Color
0#544025320400VGA/Mono, VGA/Color, VGA/Plasma
1144025320200CGA/CD, CGA/Comp, EGA/CD, EGA/ECD, [VGA/Mono], VGA/Color, [VGA/Plasma]
1*144025320350EGA/ECD, [VGA/Mono], VGA/Color, [VGA/Plasma]
1+144025360400[VGA/Mono], VGA/Color
1#144025320400[VGA/Mono], VGA/Color, [VGA/Plasma]
2548025640200[CGA/CD], CGA/Comp, [EGA/CD], [EGA/ECD], VGA/Mono, VGA/Color, VGA/Plasma
2*548025640350[EGA/ECD], VGA/Mono, VGA/Color, VGA/Plasma
2+548025720400VGA/Mono, VGA/Color
2#548025640400VGA/Mono, VGA/Color, VGA/Plasma
3148025640200CGA/CD, CGA/Comp, EGA/CD, EGA/ECD, [VGA/Mono], VGA/Color, [VGA/Plasma]
3*148025640350EGA/ECD, [VGA/Mono], VGA/Color, [VGA/Plasma]
3+148025720400[VGA/Mono], VGA/Color
3#148025640400[VGA/Mono], VGA/Color, [VGA/Plasma]
7008025720350MPA/MD, EGA/MD, VGA/Mono, VGA/Color
7+008025720400VGA/Mono, VGA/Color
7#008025640400VGA/Mono, VGA/Color, VGA/Plasma
n/a008025640350VGA/Mono, VGA/Color, VGA/Plasma
n/a148030720480[VGA/Mono], VGA/Color
n/a148030640480[VGA/Mono], VGA/Color, [VGA/Plasma]
432[40][25]320200CGA/CD, CGA/Comp, EGA/CD, EGA/ECD, [VGA/Mono], VGA/Color,[VGA/Plasma]
572[40][25]320200[CGA/CD], CGA/Comp, [EGA/CD], [EGA/ECD], VGA/Mono, VGA/Color, VGA/Plasma
631[80][25]640200CGA/CD, CGA/Comp, EGA/CD, EGA/ECD, VGA/Mono, VGA/Color, VGA/Plasma
D34[40][25]320200EGA/CD, EGA/ECD, [VGA/Mono], VGA/Color, [VGA/Plasma]
E34[80][25]640200EGA/CD, EGA/ECD, [VGA/Mono], VGA/Color, [VGA/Plasma]
F20[80][25]640350EGA/MD, VGA/Mono, VGA/Color, VGA/Plasma
1034[80][25]640350EGA/ECD, [VGA/Mono], VGA/Color, [VGA/Plasma]
1131[80][30]640480VGA/Mono, VGA/Color, VGA/Plasma
1234[80][30]640480[VGA/Mono], VGA/Color, [VGA/Plasma]
1338[40][25]320200[VGA/Mono], VGA/Color, [VGA/Plasma]
n/a118[80][30]640480[8514A/Mono], 8514A/Color
n/a114[80][30]640480[8514A/Mono], 8514A/Color
n/a118[85][38]1024768[8514A/HMono], 8514A/HColor
n/a114[85][38]1024768[8514A/HMono], 8514A/HColor
MPA       Monochrome/Printer Adapter
CGA       Color Graphics Adapter
EGA       Enhanced Graphics Adapter
VGA       Video Graphics Array, PS/2 Display Adapter
8514A     8514/A Display Adapter
MD        5151 Monochrome Display
CD        5153 Color Display
ECD       5154 Enhanced Color Display
MONO      8503 PS/2 Monochrome Display, 8507/8604 Display
HMONO     8507/8604 Display
COLOR     8512/13 PS/2 Color Display, 8514 Display
HCOLOR    8514 Display
PLASMA    Plasma Display Panel
COMP      Composite Video Monitor

Notes: #Types 0, 1, and 5 are text modes; types 2, 3, 7, and 11 are graphics modes. #For BIOS modes 0, 2, 5, the color burst is disabled on the CGA and VGA. #The Personal System/2 Display Adapter 8514/A™ has advanced function modes, which are supported through the 8514/A display adapter interface, not the VIO Subsystem. Refer to the Personal System/2 Display Adapter 8514/A Technical Reference for details of this support.

Note: For text modes in full-screen, the number of rows may differ from the mode table due to the availability of fonts of the correct size as described above.

PM Considerations

Windowable VIO sessions support only 80-column, color text modes. When VioSetMode is called from a Windowable VIO session, it only verifies that an 80-column text mode was requested, with Text Rows between 1 and 255. The resulting mode, which can be queried using VioGetMode, always has Type = 1, Color = 4, Text Columns = 80, Text Rows = requested Text Rows, Horizontal Resolution = 640, and Vertical Resolution = 16 * (Text Rows).

Family API Considerations

Some options operate differently in the DOS mode than in the OS/2 mode. Therefore, the following consideration applies to VioSetMode when coding for the DOS mode:

VioSetMode clears the screen.


C Binding

typedef struct _VIOMODEINFO {
  USHORT cb;                    /* Length of the entire data structure  */
  UCHAR  fbType;                /* Bit mask of mode being set           */
  UCHAR  color;                 /* Number of colors (power of 2)        */
  USHORT col;                   /* Number of text columns               */
  USHORT row;                   /* Number of text rows                  */
  USHORT hres;                  /* Horizontal resolution                */
  USHORT vres;                  /* Vertical resolution                  */
  UCHAR  fmt_ID;                /* Attribute format                     */
  UCHAR  attrib;                /* Number of attributes                 */
  ULONG  buf_addr;
  ULONG  buf_length;
  ULONG  full_length;
  ULONG  partial_length;
  PCH    ext_data_addr;
#define INCL_VIO
USHORT  rc = VioSetMode(ModeData, VioHandle);
PVIOMODEINFO     ModeData;      /* Mode characteristics */
HVIO             VioHandle;     /* Video handle */
USHORT           rc;            /* return code */

MASM Binding

  viomi_cb             dw ? ;Length of the entire data structure
  viomi_fbType         db ? ;Bit mask of mode being set
  viomi_color          db ? ;Number of colors (power of 2)
  viomi_col            dw ? ;Number of text columns
  viomi_row            dw ? ;Number of text rows
  viomi_hres           dw ? ;Horizontal resolution
  viomi_vres           dw ? ;Vertical resolution
  viomi_fmt_ID         db ? ;Attribute format
  viomi_attrib         db ? ;Number of attributes
  viomi_buf_addr       dd ? ;
  viomi_buf_length     dd ? ;
  viomi_full_length    dd ? ;
  viomi_partial_length dd ? ;
  viomi_ext_data_addr  dd ? ;
INCL_VIO            EQU 1
PUSH@  OTHER   ModeData      ;Mode characteristics
PUSH   WORD    VioHandle     ;Video handle
CALL   VioSetMode
Returns WORD