Q49389: Example Passing Fixed-Length String from BASIC to MASM (Far)

Article: Q49389
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom H_MASM S_QuickASM | mspl13_basic
Last Modified: 13-AUG-1990

The two programs shown below demonstrate how Microsoft BASIC passes a
fixed-length string to assembly language by far reference.

This information about interlanguage calling applies to QuickBASIC
versions 4.00, 4.00b, and 4.50 for MS-DOS, to Microsoft BASIC Compiler
versions 6.00 and 6.00b for MS-DOS and MS OS/2, and to Microsoft BASIC
Professional Development System (PDS) versions 7.00 and 7.10 for
MS-DOS and MS OS/2.

For more information about passing other types of parameters between
BASIC and MASM, search in the Software/Data Library for the following
word:

   BAS2MASM

Code Example
------------

The following BASIC program is BFSTRF.BAS, which creates a
fixed-length string and passes it to assembly language to be printed:

   DECLARE SUB RString(BYVAL sseg AS INTEGER, BYVAL soff AS INTEGER)

   DIM a AS STRING * 20

   CLS
   a = "BASIC String$" ' "$" terminates string for assembly
   CALL RString(VARSEG(a), VARPTR(a))
   END

The following program is AFSTRF.ASM, which gets a fixed-length string
from BASIC and prints it:

.MODEL MEDIUM, BASIC
.CODE
        PUBLIC RString
RString PROC
        push bp
        mov bp, sp       ; set stack frame
        push ds
        mov ds, [bp+8]   ; segment of string
        mov dx, [bp+6]   ; offset of string
        mov ah, 9        ; DOS interrupt to print string
        int 21h
        pop ds
        pop bp
        ret 4
RString ENDP
        END

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

   BC BFSTRF.BAS;
   MASM AFSTRF.ASM;
   LINK BFSTRF AFSTRF;

BFSTRF.EXE produces the following output:

   BASIC String

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