Machine code

Machine code is the processor-specific encoding of instructions that a CPU executes directly. Its instruction formats and operations are defined by the processor’s instruction set architecture.

Instruction set architecture: A processor’s specification of its instructions, registers, data types, and memory behavior. It defines which machine-code instructions a compatible processor can execute.
Binary number: A number represented using the digits zero and one. Machine-code encodings are represented as bit patterns.
Stored-program computer: A computer design in which program instructions are stored in memory alongside data. Stored programs made machine-code instruction sequences loadable and executable from memory.
Bytecode: An intermediate instruction format typically executed by a virtual machine rather than directly by a CPU. Bytecode is designed for a virtual machine, unlike processor-specific machine code.
Linker: A program that combines compiled files and libraries into an executable or shared library. A linker resolves addresses and combines machine-code sections into executable files.
Opcode: The part of an instruction encoding that specifies the operation to perform. An opcode identifies the operation represented by a machine-code instruction.
Bit: A binary digit whose value is zero or one. Bits are the smallest units in machine-code instruction encodings.
EDVAC: An early electronic computer designed around the stored-program architecture. Its design helped establish the model in which instructions are represented in memory.
Microcode: Low-level control instructions that implement some processor instructions inside a CPU. Microcode is an internal implementation layer, not usually the program code the CPU fetches.
Executable file: A file formatted so an operating system can load and run a program. Executable files contain machine code arranged for loading and execution.

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