;影响 OF、CF 标志位
;指令格式:
;MUL r/m  ;参数是乘数;如果参数是 r8/m8,   将把  AL 做乘数, 结果放在 AX
;如果参数是 r16/m16, 将把  AX 做乘数, 结果放在 EAX
;如果参数是 r32/m32, 将把 EAX 做乘数, 结果放在 EDX:EAX; Test27_1.asm
.386
.model flat, stdcallinclude    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib.dataval dd 8
.code
main proc;8 位mov al, 0FFhmul byte ptr valPrintHex ax  ;07F8;16 位mov ax, 0FFFFhmul word ptr valPrintHex dx ;0007PrintHex ax ;FFF8;32 位mov eax, 0FFFFFFFFhmul valPrintHex edx ;00000007PrintHex eax ;FFFFFFF8ret
main endp
end main;把上面的例子稍作修改(mul -> imul), 得到了不同的结果:; Test27_2.asm
.386
.model flat, stdcallinclude    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib.dataval dd 8
.code
main proc;8 位mov al, 0FFhimul byte ptr valPrintHex ax  ;FFF8;16 位mov ax, 0FFFFhimul word ptr valPrintHex dx ;FFFFPrintHex ax ;FFF8;32 位mov eax, 0FFFFFFFFhimul valPrintHex edx ;FFFFFFFFPrintHex eax ;FFFFFFF8ret
main endp
end main

IMUL: 有符号乘

;影响 OF、CF 标志位
;第一种指令格式:
;IMUL r/m  ;单操作数;如果参数是 r8/m8,   将把  AL 做乘数, 结果放在 AX
;如果参数是 r16/m16, 将把  AX 做乘数, 结果放在 EAX
;如果参数是 r32/m32, 将把 EAX 做乘数, 结果放在 EDX:EAX;以上这些都是和 MUL 一样的, 只是运算结果有时一样、有时不一样.;IMUL 还有另外两种指令格式:
;IMUL r16/r32, r16/r32/m16/m32/i  ;双操作数, (1)*(2) -> (1)
;IMUL r16/r32, r16/r32/m16/m32, i ;三操作数, (2)*(3) -> (1);其中常数 i 的位数可以 <= 但不能 > 其他操作数; Test27_3.asm
.386
.model flat, stdcallinclude    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib.dataval dd 8
.code
main proc;IMUL 两个操作数mov eax, 7imul eax, valPrintDec eax ;56;IMUL 三个操作数imul eax, val, 9PrintDec eax ;72ret
main endp
end main;MUL 与 IMUL 结果的一致于不一致:; Test27_4.asm
.386
.model flat, stdcallinclude    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib.dataval db 7Fh
.code
main proc;如果操作数都没有符号位, 结果一致mov al, 7Fhmul valPrintHex ax ;3F01mov al, 7Fhimul valPrintHex ax ;3F01;如果操作数的其中之一有符号位, 结果不一致mov al, 80hmul valPrintHex ax ;3F80mov al, 80himul valPrintHex ax ;C080;如果操作数都有符号位, 结果也一致inc valmov al, 80hmul valPrintHex ax ;4000mov al, 80himul valPrintHex ax ;4000ret
main endp
end main

DIV、IDIV: 无符号除、有符号除

;它们没有定义对 EFLAGS 的影响
;它们的指令格式:
;DIV r/m  ;参数是除数;如果参数是 r8/m8,   将把 AX      做被除数; 商 -> AL,  余数 -> AH
;如果参数是 r16/m16, 将把 DX:AX   做被除数; 商 -> AX,  余数 -> DX
;如果参数是 r32/m32, 将把 EDX:EAX 做被除数; 商 -> EAX, 余数 -> EDX; DIV 测试
; Test27_5.asm
.386
.model flat, stdcallinclude    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib.code
main proc;除数是 8 位mov ax, 17   ;被除数mov cl, 3    ;除数div clPrintDec al  ;5 - 商PrintDec ah  ;2 - 余数;除数是 16 位mov dx, 0    ;mov ax, 17   ;dx:ax 是被除数mov cx, 3    ;cx    是除数div cxPrintDec ax  ;5 - 商PrintDec dx  ;2 - 余数;除数是 32 位mov edx, 0   ;mov eax, 17  ;edx:eax 是被除数mov ecx, 3   ;ecx     是除数div ecxPrintDec eax ;5 - 商PrintDec edx ;2 - 余数ret
main endp
end main;IDIV 测试
; Test27_6.asm
.386
.model flat, stdcallinclude    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib.code
main proc;除数是 8 位mov al, -17   cbw          ;ax 是被除数mov cl, 3    ;除数idiv clPrintDec al  ;-5 - 商PrintDec ah  ;-2 - 余数;除数是 16 位mov ax, -17   cwd          ;dx:ax 是被除数mov cx, 3    ;cx    是除数idiv cxPrintDec ax  ;-5 - 商PrintDec dx  ;-2 - 余数;除数是 32 位mov eax, -17  cdq          ;edx:eax 是被除数mov ecx, 3   ;ecx     是除数idiv ecxPrintDec eax ;-5 - 商PrintDec edx ;-2 - 余数ret
main endp
end main