最后，DOCTYPE项允许我们引用特殊DTD，而不需要使用正式公共标识或实际的文件名。

Lastly, the DOCTYPE entry allows us to refer to a particular DTD without using the formal public identifier or an actual filename.

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其次，操作系统项，将创建指定的操作系统映像和引用 RAMDISK 设备对象 （通过其全局唯一标识符或 GUID）。

Second, an operating system entry is created that specifies the operating system image and references the RAMDISK device object (by its globally unique identifier, or GUID).

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