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Browse Prior Art Database

Personal Computer Screen Switchable Mode

IP.com Disclosure Number: IPCOM000103620D
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 5 page(s) / 191K

Publishing Venue

IBM

Related People

Miller, RV: AUTHOR [+2]

Abstract

Described is a software implementation to enable a personal computer (PC) screen image to be rotated to either portrait or landscape modes. The implementation utilizes the basic input/output support (BIOS) functions of the PC to obtain the two modes.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 26% of the total text.

Personal Computer Screen Switchable Mode

       Described is a software implementation to enable a
personal computer (PC) screen image to be rotated to either portrait
or landscape modes.  The implementation utilizes the basic
input/output support (BIOS) functions of the PC to obtain the two
modes.

      In prior art, BIOS treated all screen images in only landscape
mode.  The concept described herein enables the user to switch the
display mode so that the display can be rotated 90o without
necessitating any programming changes.  Although prior-art
implementations for the switchable mode exist, they are not
implemented in BIOS.

      The following outlines the BIOS support involved:
  1.  Configure Device: Through diagnostics or application programs
  2.  Application Program: Use standard PC display for input/output
(I/O) as follows:
  3.  BIOS: Test mode (Landscape/Portrait)
            Adjust screen geometry as per mode
            Use appropriate font definition

      The following lists the functions of the INT 10H of the PC that
can be used in either portrait or landscape mode:
     (AH) - 00H  - Set Mode
     (AH) - 02H  - Set Cursor Position
     (AH) - 03H  - Read Cursor Position
     (AH) - 05H  - Select Active Display Page
     (AH) - 006  - Scroll Active Page Up
     (AH) - 07H  - Scroll Active Page Down
     (AH) - 08H  - Read Attribute/Character at Current Cursor
Position
     (AH) - 09H  - Write Attribute/Character at Current Cursor
Position
     (AH) - 0AH  - Write Character at Current Cursor Position
     (AH) - 0EH  - Write Teletype to active page
     (AH) - 0FH  - Read Current Video State
     (AH) - 11H  - Character Generator
     (AH) - 13H  - Write String
     (AH) - 14H  - Load Liquid Crystal Diode (LCD) Character Font

      The functions can be used by either the operating system or any
application program without regard to the display orientation,
thereby providing a completely transparent and fully compatible mode
of operation.  When one mode is switched to another, the number of
rows becomes the number of columns and the number of columns becomes
the number of rows.  The concept applies to character mode, graphics
mode, and by definition to landscape mode.  Screen coordinates and
origin are changed as per the orientation of the display.  The
following programming interface is compatible with the PC BIOS
interface in both portrait and landscape modes:
     Interrupt 10H - (AH) = 00H - Set Mode:
     Input: (AH) = 00H - Set Mode
            (AL) = Contains Mode Value as follows:
          TYPE        RES/DIM       MAX PAGES       NOTES
  (AL)=0   ALPHA       40 x 25           8
  (AL)=1   ALPHA       40 x 25           8
  (AL)=2   ALPHA       80 x 25           8
  (AL)=3   ALPHA   ...