Q64106: Sample Assembly Function Returning Single to BASIC

Article: Q64106
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | H_MASM S_QUICKASM B_BasicCom SR# S900718-21 | mspl13_basic
Last Modified: 10-AUG-1990

The two programs below demonstrate how an assembly language function
can return a single-precision variable to a Microsoft BASIC program.

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 or the Knowledge
Base for the following word:

   BAS2MASM

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

The following BASIC program is SFUNC.BAS, which displays a
single-precision number returned from an assembly language function:

   DECLARE FUNCTION QPrint!
   FOR i% = 1 to 2
      PRINT QPrint!
   NEXT

The following program is ASING.ASM, which will return a
single-precision number when called:

; The following handy .MODEL MEDIUM,BASIC directive is found in MASM
; 5.10 but not in earlier versions:
.MODEL MEDIUM, BASIC
.DATA
        singlenum dd 98.6

.CODE
        PUBLIC QPrint
QPrint  PROC FAR
        push bp
        mov bp, sp
        push si
        push di
        push es

        push ds         ; set es = ds
        pop es

        mov si, offset dgroup:singlenum
        mov di, [bp+6]  ; load value into address at bp+6

        mov cx, 4
        rep movsb

        mov ax, [bp+6]  ; load offset of temp value in ax and
        mov dx, ss      ; ss into dx

        pop es
        pop di
        pop si
        pop bp
        ret 2
QPrint  ENDP
        END

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

   BC IFUNC.BAS;
   MASM ASING.ASM;
   LINK IFUNC ASING;

IFUNC.EXE produces the following output:

   98.6
   98.6

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