A debugger extension is an entry point in a DLL called by NTSD. Debugger extensions are called when NTSD sees the following command:
![module-name.] extension-name [extension-arguments]
If the module name is specified, it is loaded into NTSD using a call to LoadLibrary(module-name). Otherwise, the default extension module is loaded using LoadLibrary("ntsdexts").
After NTSD has loaded the extension library, NTSD calls GetProcAddress to locate the extension name in the extension module. The extension name is case sensitive and must be entered exactly as it appears in the extension module's .DEF file. If the extension address is found, the extension is called.
The header file NTSDEXTS.H specifies the extension protocol.