8.2 I/O Instructions I/O指令 The I/O instructions of the 80386 provide access to the processor's I/O ports for the transfer of data to and from peripheral devices. These instructions have as one operand the address of a port in the I/O address space. T
call和ret都是用来修改ip或cs:ip,可以用来实现子程序的设计: 1.ret和retf ret ->修改ip的内容,从而实现近转移: retf ->同时修改cs和ip,从而实现远转移: 执行ret时:相当于 pop ip 1](ip)=((ss)*16+(sp)):也就是将栈顶的值赋值给ip: 2](sp)=(sp)+2:也就是栈顶指向栈的下一个字: 执行retf时:相当于pop ip,pop cs 1](ip)=((ss)*16+(sp))