Bytecode

Bytecode is a low-level, platform-neutral instruction set designed for execution by a virtual machine rather than physical hardware. It occupies the middle ground between high-level source code and machine-specific assembly: more abstract than x86 or ARM instructions, but concrete enough to represent control flow, arithmetic operations, and memory access directly. Java compiles to JVM bytecode; Python compiles to CPython bytecode; the Ethereum virtual machine executes EVM bytecode.

The invention of bytecode was a recognition that portability and performance need not be mutually exclusive. By standardizing an intermediate representation, bytecode enables just-in-time compilation, ahead-of-time compilation, and sophisticated runtime optimizations that would be impossible if every compiler targeted physical hardware directly. Bytecode is the lingua franca of the virtualized world — and as virtualization becomes the default mode of computing, bytecode may be closer to the true "machine language" of the 21st century than any silicon instruction set.