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A hardfork is a protocol change.

• tscs37 9y ago
  Not really, a hardfork is a explicit change in consensus, everyone decides that despite the code saying A, we do B. The underlying code is overridden for a single block before reasserting it with full authority but it does not affect the protocol. The clients and nodes in the network communicate and operate just as before, in fact, a client without the hardfork code can still receive and process the hardfork block but reject it due to not being compatible with it's consensus machine. However, this is one layer above the protocol that makes up the Ethereum network. The protocol is merely interested in the validity of a block, not how to achieve this conclusion. If you wrote a client that simply accepted all blocks as valid, it would accept this hardfork without problem, sans not having a correct balance record anymore. What it would not accept is one of the newer hardforks because those actually changed the protocol and EVM to some extend, making it not understandable to old clients. Those could be interpreted as actual protocol changes.