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August 10, 2022, 06:12:30 PM Last edit: August 10, 2022, 09:00:44 PM by achow101 |
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They are literally unused and are unusable because they do not appear in the script interpreter. The main loop of the interpreter doesn't handle OP_RESERVED, and the default for unhandled opcdoes is to immediately fail. This behavior has existed since the original 0.1.0 release.
The are likely named OP_RESERVED because Satoshi was probably saving some space to add new opcodes in the future. However the only way to change the behavior of these opcodes is to do a hard fork which redefines them to only fail under specific conditions. Since the original release, the OP_NOP opcodes were added (which would also have been a hard fork), and with Taproot, OP_SUCCESS. These opcodes allow us to introduce new opcodes as soft forks.
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