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
