Representing programs as instructions
A compiler can translate source code into instructions defined by a virtual machine. Bytecode is this intermediate program representation, rather than the programmer’s original text or necessarily the native instructions of the host processor. Loads, calculations, branches, and calls receive meanings from the instruction set of the particular runtime.
Supplying operands to instructions
Many JVM instructions consume values from an operand stack and place results back on it. Other machines can organize operands differently. Encodings distinguish operation codes from accompanying operands or additional data, so the word bytecode does not imply that every complete instruction must occupy exactly one byte.
Inspecting the intermediate form
A disassembler displays bytecode as readable instructions, revealing how source expressions were decomposed. Python’s dis module provides such an interface, but its documentation identifies CPython bytecode as an implementation detail without cross-version or cross-VM guarantees. Inspection describes a particular execution system rather than a universal permanent Python format.
References: [2]
Different ways to execute one representation
A runtime may interpret virtual instructions or compile them further into native code, so bytecode alone does not determine performance. The JVM specification and CPython implementation also have different compatibility commitments. Portability claims must identify the supported runtime and version rather than promise execution on every possible device.