The Microsoft Macro Assembler Version 5.10 includes several new
features (not found in MASM Version 5.00 or earlier) that simplify
assembly-language routines linked with high-level language programs
Two of these features are as follows:
- An extension to the .MODEL directive that automatically sets up
naming, calling, and return conventions for a given high-level
language; for example, .MODEL MEDIUM,Basic
- A modification of the PROC directive that handles most of the
procedure entry automatically. The PROC directive saves specified
registers, defines text macros for passed arguments, and generates
stack setup code on entry and stack tear-down code on exit.
These new features are supported by QuickBasic Versions 4.00, 4.00b,
and 4.50 and the Microsoft Basic Compiler Versions 6.00 and 6.00b.
Section 5 of the "Microsoft Macro Assembler 5.1: 5.1 Update" manual
discusses the new features.
Page 332 of the "Microsoft QuickBasic Version 4.00: Learning and Using
QuickBasic" manual provides an example of an assembly-language
function called by Basic. The example from Page 332 is modified below
to demonstrate the new features in the Microsoft Macro Assembler
Compile and Link Instructions are as follows:
LINK power + powera;
The following is the Basic Program, POWER.BAS, which invokes the
assembly language function POWER2:
DECLARE FUNCTION power2 (x%, y%)
PRINT power2(3, 5)
The following is POWER2.ASM, an example of using the extended .MODEL
and .PROC directives in MASM 5.10:
.model medium,Basic ;Adds the language option ",Basic"
;PUBLIC directive was removed. The label on
;the PROC directive is now the function name.
Power2 PROC arg1:word, arg2:word ;parameters added to PROC
;Note: PUSH BP and MOV BP,SP are no longer needed.
;The arguments are refered to by the names supplied on the
;PROC list instead of their offset from BP (Base Pointer):
;Note, POP BP is no longer needed.
ret ;RET is used now, instead of RET n, (where n is
;two times the number of passed arguments.)
For comparison, the following is the equivalent, earlier (MASM Version
5.00) form for POWER2.ASM, taken from Page 332 of "Learning and Using
QuickBasic" (for Versions 4.00 and 4.00b, and Basic Compiler Versions
6.00 and 6.00b):
MOV BP,SP ; Set stack framepointer
mov bx,[bp+8] ; Load Arg1 into
mov ax,[bx] ; AX
mov bx,[bp+6] ; Load Arg2 into
mov cx,[bx] ; CX
shl ax,cl ; AX = AX * (2 to power of CX)
; Leave return value in AX
POP BP ; Exit sequence -- restore old BP
ret 4 ; Return and restore 4 bytes.
Article ID: 39381 - Last Review: February 27, 2014 - Revision: 1.2
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