_arrysum.asm

此为本书配套光盘.本书主要内容包括：微型计算机基础知识、IBM-PC微型计算机系统概述、汇编语言程序设计基本方法、三大结构程序设计、子程序设计、汇编语言程序设计等内容。

TITLE ArraySum Procedure                 (_arrysum.asm)

INCLUDE sum.inc

.code
;-----------------------------------------------------
ArraySum PROC,
	ptrArray:PTR DWORD,	; pointer to array
	arraySize:DWORD	; size of array
;
; Calculates the sum of an array of 32-bit integers.
; Returns:  EAX = sum
;-----------------------------------------------------
	push ecx	; don't push EAX
	push esi

	mov  eax,0	; set the sum to zero
	mov  esi,ptrArray
	mov  ecx,arraySize
	cmp  ecx,0	; array size <= 0?
	jle  AS2	; yes: quit

AS1:
	add  eax,[esi]	; add each integer to sum
	add  esi,4	; point to next integer
	loop AS1	; repeat for array size

AS2:
	pop esi
	pop ecx	; return sum in EAX
	ret
ArraySum ENDP
END