• 实验任务2
• 实验任务3
• 实验任务4
• 实验任务5
• 实验任务6
• 实验任务7

实验任务2

因为是 ROM 里的数据，所以不可修改。

实验任务3

实验任务4

 -a
 mov ax, 20
 mov ds, ax
 mov ss, ax
 mov sp, 30
 push [0] 	; 执行后,寄存器(sp) = 2E
 push [2] 	; 执行后,寄存器(sp) = 2C
 push [4] 	; 执行后,寄存器(sp) = 2A
 push [6] 	; 执行后,寄存器(sp) = 28
 pop [6]	; 执行后,寄存器(sp) = 2A
 pop [4] 	; 执行后,寄存器(sp) = 2C
 pop [2]	; 执行后,寄存器(sp) = 2E
 pop [0]	; 执行后,寄存器(sp) = 30

1. 逻辑地址: ss:30H 物理地址: ss:30H = $20H \times 16 + 30H = 230H$

2. 

3. 前:

   

   后:

   

   不变

4. 

实验任务5

1. 没有暂停。 mov sp, 30 立刻执行了。

   参考 MASM Reference^[1] 和 64-ia-32-architectures-software-developer-vol-3a-part-1-manual^[2]。

   MASM Reference: Moves the value in the source operand to the destination operand. If the destination operand is SS, interrupts are disabled until the next instruction is executed (except on early versions of the 8088 and 8086).

2. 栈空间00220H ~ 0022fH内存单元值是调用 interrupt-handler 得到的数据。^[3]

   When the processor performs a call to the exception- or interrupt-handler procedure:
   When the stack switch occurs:
   a. The segment selector and stack pointer for the stack to be used by the handler are obtained from the TSS
   for the currently executing task. On this new stack, the processor pushes the stack segment selector and
   stack pointer of the interrupted procedure.
   b. The processor then saves the current state of the EFLAGS, CS, and EIP registers on the new stack (see
   Figures 6-4).
   c. If an exception causes an error code to be saved, it is pushed on the new stack after the EIP value.

实验任务6

1. 源码

   assume cs:code
   
   code segment
   start:
   	mov cx, 10
   	mov dl, '0'
   s: 	mov ah, 2
   	int 21h
   	add dl, 1
   	loop s
   	
   	mov ah, 4ch
   	int 21h
   code ends
   end start
   

2. 汇编链接过程截图以及运行可执行程序的运行结果截图

3. 程序段前缀PSP的截图

实验任务7

assume cs:code
code segment
    mov ax, cs
    mov ds, ax
    mov ax, 0020h
    mov es, ax
    mov bx, 0
    mov cx, 17h
s:  mov al, [bx]
    mov es:[bx], al
    inc bx
    loop s
    mov ax, 4c00h
    int 21h
code ends
end

• By default, instructions that use direct memory addressing use the DS register.^[4]我们需要 mov al, [bx] 从 cs 段开始复制数据，所以 mov ds, ax
• 通过 debug 直接查出需要复制的数据占 17H 字节。也可以查手册一条指令一条指令计算，太麻烦了。

上古 8086，参考好难找，Intel 64 手册凑合用。