Demo: Copy a File Using a Global Buffer

The first of three variants of the same program: a small cp, taking a source and a destination file as command-line arguments. This variant stages the data through a static global buffer — memory that exists for the whole lifetime of the process, laid out by the compiler before main() ever runs, with no allocation and nothing to release.

Together with the teaching assistant you will fill in the TODOs in copy_file.c, build it, copy a file and check the result byte for byte. Keep an eye on where the buffer lives and what that costs: the next two variants copy exactly the same bytes with the memory obtained in two very different ways.