汇编-CDQ将有符号数双字转换为四字

 将eax寄存器中的有符号数扩展为edx:eax中的有符号数。如果eax是正数，则edx会被设置为00000000h；如果eax是负数，则edx会被设置为FFFFFFFFH

.386  
.model flat,stdcall 
option casemap:none
.stack 4096

Include Irvine32.inc
includelib Irvine32.lib

ExitProcess PROTO,dwExitCode:DWORD  
 
.data   
packed_1 WORD 4536h 
packed_2 WORD 7207h 
sum DWORD ?

 
.code   
main PROC   
    
    
    mov eax,-5  ;edx=xxh   eax=FFFFFFFBh
    CDQ
    ;EDX = FFFFFFFFh     EAX = FFFFFFFB



    INVOKE ExitProcess,0  
main ENDP   
END main