Definition
An opcode (operation code) is a low-level instruction identifier used by a virtual machine or processor to specify a particular operation to execute. In blockchain contexts, opcodes define the discrete computational steps that a smart contract execution environment recognizes, with each opcode corresponding to a specific, enumerated action on data, control flow, storage, or the execution stack.
In Simple Terms
An opcode is a code that tells a blockchain’s execution engine exactly which basic action to perform. It is one of many predefined, low-level commands that smart contract platforms understand, such as moving data, doing arithmetic, or changing stored values, expressed in a compact, machine-readable form.
Context and Usage
In blockchain systems that use virtual machines, opcodes constitute the fundamental instruction set for executing smart contract bytecode. They are central to how contract logic is represented at the system level and are directly tied to resource accounting and execution rules. Discussion of opcodes commonly appears in low-level contract analysis, virtual machine specifications, gas accounting models, and security reviews of compiled contract code.