Copy-on-write fork simulator

Problem

Simulate copy-on-write. Input: the number of pages of process P (frames 0 … n−1, one per page), then operations:

fork A B — process B becomes a child of A: B's page table is a copy of A's (frames are shared, their reference counts increase). Print fork A -> B: n pages shared read-only, 0 copied.
X read k — print X read k: frame f.
X write k — if X's frame for page k is shared (reference count > 1), copy it to a new frame (the next unused frame number), decrement the old frame's count: X write k: COW fault, copy frame f -> frame g; otherwise X write k: frame f (private, no copy).

At the end print COW faults: c, pages copied: c, frames in use: u (frames with a count > 0) and Eager fork would have copied: e pages (t frames), where each fork would copy all n pages and t = number of processes × n.

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