Opcode
An encoded instruction interpreted by a virtual machine or transaction script engine.
An opcode identifies an operation in a virtual machine, such as pushing data, comparing values, hashing bytes, checking a signature, or controlling execution.
The same numeric code can be active, disabled, reserved, or assigned different semantics under another protocol or VM version. Opcode behavior must be read from the exact consensus specification and implementation target.
Execution remains subject to stack, transaction, validation-cost, and standardness limits. Adding an opcode can expand contract capability while also creating compatibility and resource-exhaustion risks.
Related terms
Explore connected entries beyond the alphabetical index.
Smart Contract
→Blockchain-enforced program or script logic that controls how assets or state may change.
Bitcoin Script
→The stack-based spending-condition language used by Bitcoin-family transaction outputs.
OP_RETURN
→A script opcode commonly used to create a provably unspendable output carrying a limited data payload.
CashVM
→An ecosystem name for the stack-based virtual machine that evaluates Bitcoin Cash spending bytecode.