Example of Passing Basic String Descriptor to MASM (Near) (49384)

SUMMARY

The two programs below demonstrate how a Microsoft Basic program passes a Basic string descriptor to assembly language by near 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.

MORE INFORMATION

For more information about passing other types of parameters between Basic and MASM, search in the Microsoft Knowledge Base using the following word:

BAS2MASM

Code Example

The following Basic program is BSTRN.BAS, which passes a string descriptor to assembly language by near reference:

   DECLARE SUB RString(A AS STRING)
   A$ = "This is the String" + "$"  ' "$" terminates the string
                                    '     for INT call
   CALL RString(A$)
   END

The following program is ASTRN.ASM, which gets a string descriptor from Basic by near reference and prints the string out:

; The following handy .MODEL MEDIUM,Basic directive is found in MASM
; 5.10 but not in earlier versions:
.MODEL MEDIUM, Basic
.CODE
        PUBLIC RString
RString PROC
        push bp
        mov bp, sp
        mov bx, [bp+6]     ; get offset of string descriptor
        mov dx, [bx+2]     ; get address of string
        mov ah, 9          ; int call to print string
        int 21h
        pop bp

        ret 2
RString ENDP

        END

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

BC BSTRN.BAS;
MASM ASTRN.ASM;
LINK BSTRN ASTRN;

BSTRN.EXE produces the following output:

This is the string