bytecodes

Bytecode is a form of instruction set designed for efficient execution by a software interpreter or virtual machine instead of directly by hardware. Typically produced by compiling a high-level language into an intermediate, platform-independent representation, bytecode can be executed on any system that has a compatible virtual machine. This contrasts with native machine code, which is tailored to a specific processor architecture.

Most bytecode formats are designed to be portable and safe. They are often either stack-based, with instructions that manipulate an evaluation stack, or register-based, where operations target a set of virtual registers. Java bytecode runs on the Java Virtual Machine, Python bytecode on the Python interpreter, and .NET bytecode (CIL) on the Common Language Runtime. Android’s Dalvik/DEX format is another notable example.

Execution typically uses interpretation or dynamic translation. Just-in-time compilation can convert bytecode to native code at runtime, improving performance. Verification and safety checks are common before execution to prevent illegal memory access and to enforce type safety. Bytecode’s portability and sandboxing make it attractive for cross-platform software, education, and dynamic languages.

Limitations include overhead from the runtime environment and typically lower peak performance than optimized native code. The VM or runtime also defines the supported features and libraries. Despite these trade-offs, bytecode remains a core component of many language ecosystems, enabling portability, rapid deployment, and runtime optimization strategies such as JIT and, in some systems, ahead-of-time compilation.