『第 2 楼』:
使用 LLM 解释/回答一下
在 grub4dos 中，一个文件的所谓“连续性”是指这个文件在磁盘上的物理存放位置是一整块连续的扇区序列，中间没有“空洞”。或者用通俗的语言来说，一个“连续”的文件，就是一个“没有碎块”的文件。
操作系统所建立的文件，不一定是连续的。一个文件可能被分为很多个碎块。contig 和 wincontig 命令能够把一个不连续的文件整理成连续的文件。我用过 contig 命令，但是，它可能还不能一下子就整理完毕，可能需要多次整理，才可以最终整理成一个连续的、没有碎块文件。
map 命令能够检测到一个文件是否连续，对于不连续的文件，map 拒绝仿真它。但 map --mem 的情况不需要文件是连续的，因为此时 map 会把不连续的映像文件的各个碎片拷贝到内存，变成（内存中的）一个连续的映像文件。
由于 map 的仿真代码不使用 DOS 而只使用主板的 BIOS，所以，在 DOS 下可以访问的普通不连续的文件，在 map 的仿真代码看来就无法访问。BIOS 只认得“扇区”这个概念，不认得“文件”这个概念。而仿真代码只使用 BIOS，所以，也就不认得 DOS 的文件了。但是，当 DOS 的文件被整理成连续之后，它就变成一整块的“扇区”序列了，于是，仿真代码也就能够方便地访问它了。原则上讲，仿真代码也可设计为支持具有多个碎块的映像文件，但是，这个工作量很大，处理起来比较麻烦，实现起来有一定的困难。
grub4dos 目前已经支持软盘、硬盘以及光盘的仿真。最新的 memdisk 也已经支持这些仿真。ISO 仿真就是指用 ISO 文件来仿真光盘。
In grub4dos, the so-called "continuity" of a file means that the physical storage location of this file on the disk is a continuous sequence of sectors without "holes". Or in plain language, a "continuous" file is a "non-fragmented" file.
The files created by the operating system are not necessarily continuous. A file may be divided into many fragments. The contig and wincontig commands can organize a discontinuous file into a continuous one. I have used the contig command, but it may not be completed at one go, and may need to be organized multiple times before it can finally become a continuous, non-fragmented file.
The map command can detect whether a file is continuous. For a discontinuous file, the map refuses to simulate it. But in the case of map --mem, the file does not need to be continuous, because at this time map will copy each fragment of the discontinuous image file to memory and become a continuous image file (in memory).
Since the simulation code of map uses the BIOS of the motherboard instead of DOS, the ordinary discontinuous files that can be accessed under DOS cannot be accessed in the eyes of the simulation code of map. The BIOS only recognizes the concept of "sector" and does not recognize the concept of "file". And the simulation code only uses the BIOS, so it does not recognize DOS files. However, when a DOS file is organized into a continuous one, it becomes a continuous sequence of "sectors", so the simulation code can then access it conveniently. In principle, the simulation code can also be designed to support image files with multiple fragments, but this requires a lot of work, is more complicated to handle, and is difficult to implement.
grub4dos currently supports the simulation of floppy disks, hard disks, and optical disks. The latest memdisk also supports these simulations. ISO simulation means using an ISO file to simulate an optical disk.
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