Update README.md

README.md

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 # NTV04_NtShutdownSystem
-NTAPI快速关闭计算机视频源代码，用于演示未公开的AP
+NTAPI快速关闭计算机视频源代码，用于演示未公开的API - NtShutdownSystem
+
+## 关于NtShutdownSystem
+
+### 函数原型
+```c++
+DWORD NtShutdownSystem(SHUTDOWN_ACTION Action);
+```
+
+### 函数指针类型
+```c++
+typedef DWORD(WINAPI* typeNtShutdownSystem)(SHUTDOWN_ACTION Action);
+```
+
+### 未导出类型
+ - SHUTDOWN_ACTION
+```c++
+typedef enum _SHUTDOWN_ACTION
+{
+    ShutdownNoReboot,
+    ShutdownReboot,
+    ShutdownPowerOff
+} SHUTDOWN_ACTION;
+```
+
+### 所在DLL
+ - ntdll.dll