关于实验16的测试代码执行问题

FishC

你的问题可能与以下几个方面有关：

1. **中断处理程序未正确返回**  
   你的代码调用 `int 7ch` 之后，可能没有正确返回，导致程序停滞。你可以检查 `int 7ch` 对应的中断处理程序是否正确执行 `iret` 返回。

2. **中断 7Ch 可能未正确注册**  
   你调用 `mov ax, 102h` 和 `mov ax, 204h` 进行中断调用，但如果 `int 7ch` 处理程序没有正确安装，可能会导致后续代码无法执行。

3. **DOS 环境下的调试问题**  
   强制关闭 DOS 窗口后，可能会导致中断向量表未恢复，影响后续的测试。建议在程序退出时，确保恢复原始的中断向量。

### 解决方案：
- **确保 `int 7ch` 处理程序正确安装**，并在 `iret` 之前正确保存和恢复寄存器。
- **在程序退出时恢复原始中断**，避免影响后续测试。
- **使用 `debug` 或 `TD`（Turbo Debugger）检查 `int 7ch` 的执行情况**，看看是否正确返回。

如果你能提供 `int 7ch` 具体的中断处理代码，我可以帮你进一步分析。

以上回复来自 FishC AI 小助理，如未能正确解答您的问题，请继续追问。

FishC

laocaiye 发表于 2025-03-21 15:05
以下是安装程序

assume cs:code

code segment
...

It looks like you're implementing a custom interrupt handler at `int 7Ch`, but you're encountering issues where the interrupt only executes once, the screen freezes, and subsequent executions do not work. Let's analyze the potential causes and solutions.

---

### **Potential Issues**
1. **Interrupt Handler Not Properly Installed**
   - Your installation code copies the interrupt handler to `0:200h`, but it does not properly set the interrupt vector for `int 7Ch`. Instead, it modifies `es:[0]` and `es:[2]`, which are likely affecting `int 00h` (Divide by Zero Exception) instead of `int 7Ch`.

2. **Interrupt Handler Not Returning Properly**
   - The handler should end with `iret`, which it does in `iret` at `iret: pop bx iret`. However, if the interrupt is not properly installed, it may not be executing at all.

3. **Interrupt Handler Overwriting Memory**
   - The handler modifies video memory (`0xB8000`), but if `di` is not properly managed, it could be writing outside the intended range.

4. **Interrupt Vector Not Restored**
   - If the program is forcefully closed, the interrupt vector remains pointing to an invalid memory location, causing subsequent executions to fail.

---

### **Suggested Fixes**
#### **1. Properly Set the Interrupt Vector**
Modify your installation code to correctly set `int 7Ch` in the interrupt vector table:

1. mov ax, 0
   
2. mov es, ax
   
3. mov word ptr es:[7Ch * 4], 200h  ; Offset of handler
   
4. mov word ptr es:[7Ch * 4 + 2], 0 ; Segment of handler

复制代码

This ensures that `int 7Ch` correctly points to your handler.

#### **2. Ensure the Handler Returns Properly**
Your handler should always end with `iret` to return control to the calling program.

#### **3. Restore the Original Interrupt Vector on Exit**
Before exiting, restore the original interrupt vector to prevent issues in subsequent runs.

---

### **Next Steps**
- Try modifying your installation code to correctly set `int 7Ch`.
- If the issue persists, use a debugger (`debug.exe` or `TD`) to inspect the interrupt vector at `int 7Ch` (`d 0:7C*4`).
- If you still encounter issues, let me know what happens when you run `int 7Ch` manually in a debugger.

Would you like me to provide a corrected version of your installation code?

以上回复来自 FishC AI 小助理，如未能正确解答您的问题，请继续追问。