Q50943: Using CALL INTERRUPT to Get Current SCREEN Video Mode

Article: Q50943
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S891113-112 B_BasicCom | mspl13_basic
Last Modified: 14-DEC-1989

It is possible to get the current SCREEN mode using the CALL INTERRUPT
statement in compiled BASIC. This is useful if the program does not
keep track of the current SCREEN mode, and the current video state
needs to be saved.

This information applies to Microsoft QuickBASIC Versions 4.00, 4.00b,
and 4.50 for MS-DOS, Microsoft BASIC Compiler Versions 6.00, and 6.00b
for MS-DOS, and to Microsoft BASIC PDS Version 7.00 for MS-DOS.

The following BASIC program allows you to change the video mode, then
uses CALL INTERRUPT to return the current video mode. The return
values from the CALL INTERRUPT are not the same as the BASIC SCREEN
modes, so the program creates an array that is used to translate the
returned values back to BASIC SCREEN modes.

Code Example: SCRMODE.BAS
-------------------------

REM $INCLUDE: 'qb.bi'   ' defines for CALL INTERRUPT
' For BC.EXE and QBX.EXE for BASIC 7.00, use the include file 'QBX.BI'
' and the Quick library  QBX.QLB.
DIM inregs AS regtype
DIM outregs AS regtype
DIM screenarray(19) AS INTEGER
FOR i% = 0 TO 19
        READ screenarray(i%)
NEXT
INPUT "enter screen mode: "; smode%
inregs.ax = &HF00       ' BIOS interrupt to return video mode
CALL interrupt(&H10, inregs, outregs)
smode% = outregs.ax AND &HFF   ' mask off contents of AL register
PRINT "Current screen mode = "; screenarray(smode%)
' Define conversion array for SCREEN modes
DATA 0, 0, 0, 0, 1, 1, 2, 0, 0, 0, 0, 0, 0, 7, 8, 10, 9, 11, 12, 12
END

To demonstrate this program from an .EXE program, compile and link as
follows:

   BC SCRMODE.BAS;
   LINK SCRMODE,,,QB.LIB;

For BASIC PDS 7.00, use QBX.LIB instead of QB.LIB.

If you run the program within the QuickBASIC QB.EXE editor, the
default Quick library QB.QLB must be loaded in, as follows:

   QB SCRMODE /L

For QBX.EXE 7.00, the default Quick library QBX.QLB must be loaded in,
as follows:

   QBX SCRMODE /L

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