Example of Passing Basic String Descriptor to MASM (Far) (49382)

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:

Code Example

The following Basic program is BSTRF.BAS, which passes a string descriptor (of a variable-length string) to assembly language by far reference:

    A$ = "This is the String" + "$"    ' "$" terminates the string for
                                      ' INT call
   CALLS RString(A$)   ' CALLS passes far address
   END
				

The following program is ASTRF.ASM, which gets a Basic string descriptor, then prints the string:

; The following handy .MODEL 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       ; set stack frame
        push ds
        mov ds, [bp+8]   ; segment of descriptor
        mov bx, [bp+6]   ; offset of descriptor
        mov dx, [bx+2]   ; address of actual 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: BSTRF.EXE produces the following output: