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Question: I feel it so hard to understand "CopyBeforeWrite" (also "CopyOnWrite"?), could you please give me some easy ideas to learn this?
Asked by dave (222.90.231.x) on September 20 2010, 8:22pm
Reply on September 20 2010, 9:59pm:
    A simple summary: suppose you had a sheet of paper, and on it was information you wanted to keep and possibly change. You have a monkey sitting on each side of you, and any time you go to change a word, as you're about to write over it, the monkey on your left distracts you briefly, while the monkey on the right scribbles down on a separate piece of paper the word (or paragraph containing the it) you were about to overwrite.

    Kinda like that, except instead of two monkeys, you'd have the OS kernel, which would tag the page of memory as "read only", and if you go to write it, it would cause an exception, which the kernel would handle, copying the page of memory elsewhere, and marking the old page as writeable, and resuming.
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