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by amitprasad
230 days ago
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I think I got stuck in the same rut that I learned address space in whilst writing that diagram. I would tend to agree with you that your model makes much more sense to the student. Related: In notation, one thing that I used to struggle with is how addresses (e.g. 0xAB_CD) actually have the bit representation of [0xCD, 0xAB]. Wonder if there's a common way to address that? |
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This convention started on early Intel chips and was kept for backward compatibility. It also has a practical benefit: it makes basic arithmetic and type widening cheaper in hardware. The "low" part of the value is always at the base address, so the CPU can load 8 bits, then 16 bits, then 32 bits, etc. starting from the same address without extra offset math.
So when you say an address like 0xABCD shows up in memory as [0xCD, 0xAB] byte-by-byte, that's not the address being "reversed". That's just the little-endian in-memory layout of that numeric value.
There are also big-endian architectures, where the most significant byte is stored at the lowest address. That matches how humans usually write numbers (0xABCD in memory as [0xAB, 0xCD]). But most mainstream desktop/server CPUs today are little-endian, so you mostly see the little-endian view.