pgm6_1.asm

汇编编程艺术

; Simple Arithmetic
; This program demonstrates some simple arithmetic instructions.

		.386			;So we can use extended registers
		option	segment:use16	; and addressing modes.

dseg		segment	para public 'data'

; Some type definitions for the variables we will declare:

uint		typedef	word		;Unsigned integers.
integer		typedef	sword		;Signed integers.


; Some variables we can use:

j		integer	?
k		integer	?
l		integer	?

u1      	uint	?
u2		uint	?
u3		uint	?

dseg		ends

cseg		segment	para public 'code'
		assume	cs:cseg, ds:dseg

Main		proc
		mov	ax, dseg
		mov	ds, ax
		mov	es, ax

; Initialize our variables:

		mov	j, 3
		mov	k, -2

		mov	u1, 254
		mov	u2, 22

; Compute L := j+k and u3 := u1+u2

		mov	ax, J
		add	ax, K
		mov	L, ax

		mov	ax, u1		;Note that we use the "ADD"
		add	ax, u2		; instruction for both signed
		mov	u3, ax		; and unsigned arithmetic.

; Compute L := j-k and u3 := u1-u2

		mov	ax, J
		sub	ax, K
		mov	L, ax

		mov	ax, u1		;Note that we use the "SUB"
		sub	ax, u2		; instruction for both signed
		mov	u3, ax		; and unsigned arithmetic.

; Compute L := -L

		neg	L

; Compute L := -J

		mov	ax, J		;Of course, you would only use the
		neg	ax		; NEG instruction on signed values.
		mov	L, ax

; Compute K := K + 1 using the INC instruction.

		inc	K

; Compute u2 := u2 + 1 using the INC instruction.
; Note that you can use INC for signed and unsigned values.

		inc	u2

; Compute J := J - 1 using the DEC instruction.

		dec	J

; Compute u2 := u2 - 1 using the DEC instruction.
; Note that you can use DEC for signed and unsigned values.

		dec	u2





Quit:		mov	ah, 4ch			;DOS opcode to quit program.
		int	21h			;Call DOS.
Main		endp

cseg		ends

sseg		segment	para stack 'stack'
stk		byte	1024 dup ("stack   ")
sseg		ends

zzzzzzseg	segment	para public 'zzzzzz'
LastBytes	byte	16 dup (?)
zzzzzzseg	ends
		end	Main