Q49388: Example of Passing Fixed-Length String Between BASIC and MASM
Article: Q49388 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: 10-AUG-1990 The two programs below demonstrate how Microsoft BASIC and assembly language pass fixed-length strings 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. 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 BFSTRN.BAS, which creates a fixed-length string that is passed to assembly language to print and receives a fixed-length string from assembly: DECLARE SUB RString(BYVAL offs AS INTEGER) TYPE fixstring s AS STRING * 20 END TYPE DIM a AS STRING * 20 CLS a = "BASIC String$" ' "$" terminates string for assembly CALL RString(VARPTR(a)) END SUB BasicSub(a AS fixstring) LOCATE 2, 1 ' Must LOCATE because print in assembly won't move PRINT a.s ' BASIC's screen position END SUB The following program is AFSTRN.ASM, which gets a fixed-length string by near reference, prints the string, then passes a string to a BASIC subprogram: ; The following handy .MODEL directive is found in MASM 5.10 but not ; in earlier versions: .MODEL MEDIUM, BASIC EXTRN BasicSub:PROC .DATA astr DB 'Assembly String ' .CODE PUBLIC RString RString PROC push bp mov bp, sp ; set stack frame mov dx, [bp+6] ; address of string mov ah, 9 ; DOS interrupt to print string int 21h mov ax, OFFSET astr ; address of assembly string push ax ; pass it to BASIC call BasicSub pop bp ret 2 RString ENDP END To demonstrate these programs from an .EXE program, compile and link as follows: BC BFSTRN.BAS; MASM AFSTRN.ASM; LINK BFSTRN AFSTRN; BFSTRN.EXE produces the following output: BASIC String Assembly String
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