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   Microsoft Product Support Services Application Note (Text File)
    HF0405: CALLING DOS AND BIOS INTERRUPTS WITH FORTRAN AND MASM
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                                                   Revision Date: 8/91
                                                       1 Disk Included

This information applies to Microsoft FORTRAN versions 5.0 and 5.1.

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This application note illustrates how to access DOS interrupts without
using the functions INTDOS and INTDOSX. DOS and BIOS interrupts can
be called by specifying the interrupt number and the input register
values within the main program. INTERRUPT and INTERRUPTX differ from
the INTDOS and INTDOSX routines included with FORTRAN in that
interrupts other than interrupt 21 can be called.

Included on the enclosed "Calling DOS and BIOS Interrupts with FORTRAN
and MASM" disk are the following files. These files define the
INTERRUPT and INTERRUPTX functions and provide two FORTRAN sample
programs demonstrating how these functions are called.

File           Description
----           -----------

INTERRPT.ASM   The assembly source listing of the INTERRUPT and
               INTERRUPTX routines.

INTERRPT.INC   An include file for INTERRUPT and INTERRUPTX. This
               file contains the INTERFACE to the assembly routines
               and the register structures needed for INTERRUPT and
               INTERRUPTX.

INTERRPT.OBJ   The preassembled version of INTERRPT.ASM to be linked
               with programs calling INTERRUPT or INTERRUPTX.

INT.FOR        FORTRAN sample program that demonstrates how to use the
               INTERRUPT function call. INT.FOR uses INT 21, function
               2A hex to get the system date.

INTX.FOR       FORTRAN sample program using segment registers that
               demonstrates how to use the INTERRUPTX function call.
               INTXFOR uses INT 21, function 41 hex to delete a file.

INT.EXE        Executable version of INT.FOR example.

INTX.EXE       Executable version of INTX.FOR example.

The two assembly language routines included in INTERRPT.ASM are as
follows:

1. INTERRUPT(INTNUM,INREGS,OUTREGS) invokes the interrupt specified by
   INTNUM using the values of INREGS and returns the result of the
   interrupt call in OUTREGS.

2. INTERRUPTX(INTNUM,INREGS,OUTREGS) invokes the system in the same
   manner as INTERRUPT but accepts segment register values.

To use the INTERRUPT and INTERRUPTX functions, the statement

   INCLUDE 'INTERRPT.INC'

must be located at the top of the source file where a call is made to
the assembly language procedures. The two statement function
definitions documented at the end of the INTERRPT.INC file must be
uncommented and added to the source code of any FORTRAN program,
function, or subroutine block where the assembly language procedures
are called.

The statement functions documented at the end of INTERRPT.INC are
shown below. These statement functions must appear before any
executable statements. INTERRPT.OBJ must then be linked with the
object file produced from compiling the main program.

   gethibyte (dataword) = dataword / 256
   getlobyte (dataword) = iand(dataword , 255)

Microsoft cannot guarantee that the information stated here regarding
how to use INTERRUPT and INTERRUPTX will allow you to perform all MS-
DOS system or BIOS calls correctly because this information has not
been tested rigorously and is not considered a feature of the product.