machine code - meaning and definition. What is machine code
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What (who) is machine code - definition

Native code; Machine instruction; Machine Code; Machine language; Machine Language; Native applications; Native execution; Machine instruction (computing); Program machine code; Machine instructions; CPU instruction; CPU instructions; Opcode-level programming; Opcode level; Overlapping instructions; Overlapping instruction; Overlapping machine instructions; Overlapping machine instruction; Overlapping opcodes; Overlapping opcode; Overlapping opcode sequences; Overlapping opcode sequence; Overlapping op-codes; Overlapping op-code; Overlapping op-code sequences; Overlapping op-code sequence; Superpositioned code; Code superposition; Instruction overlapping; Code overlapping; Instruction scission; Opcode overlapping; Jump into the middle of instruction; Instruction overlapping technique; Jump in the middle; Jump into the middle of an instruction; Jumping into the middle of an instruction; Jumping into the middle of instruction; Code overlap; Overlapping code; Overlapped instruction encoding; Overlapped instruction; Overlapped instructions; Semantic code overlapping; Semantic overlapping (computing); Physical overlapping (computing); Physical code overlapping; Overlapped code; Code interleaving; Code outlining; Overlapping instruction sequences; Overlapping instruction sequence; Code-overlapping technique
  • code disassembly]], as well as processor register and memory dumps.

machine code         
Machine code is a way of expressing instructions and information in the form of numbers which can be understood by a computer or microchip. (COMPUTING)
machine code         
(also machine language)
¦ noun a computer programming language consisting of binary or hexadecimal instructions which a computer can respond to directly.
machine code         
The representation of a computer program which is actually read and interpreted by the computer. A program in machine code consists of a sequence of machine instructions (possibly interspersed with data). Instructions are binary strings which may be either all the same size (e.g. one 32-bit word for many modern RISC microprocessors) or of different sizes, in which case the size of the instruction is determined from the first word (e.g. Motorola 68000) or byte (e.g. Inmos transputer). The collection of all possible instructions for a particular computer is known as its "instruction set". Execution of machine code may either be hard-wired into the central processing unit or it may be controlled by microcode. The basic execution cycle consists of fetching the next instruction from main memory, decoding it (determining which operation it specifies and the location of any arguments) and executing it by opening various gates (e.g. to allow data to flow from main memory into a CPU register) and enabling functional units (e.g. signalling to the ALU to perform an addition). Humans almost never write programs directly in machine code. Instead, they use a programming language which is translated by the computer into machine code. The simplest kind of programming language is assembly language which usually has a one-to-one correspondence with the resulting machine code instructions but allows the use of mnemonics (ASCII strings) for the "op codes" (the part of the instruction which encodes the basic type of operation to perform) and names for locations in the program (branch labels) and for variables and constants. (1995-02-15)


Machine code

In computer programming, machine code is computer code consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). Each instruction causes the CPU to perform a very specific task, such as a load, a store, a jump, or an arithmetic logic unit (ALU) operation on one or more units of data in the CPU's registers or memory.

Early CPUs had specific machine code that might break backwards compatibility with each new CPU released. The notion of an instruction set architecture (ISA) defines and specifies the behavior and encoding in memory of the instruction set of the system, without specifying its exact implementation. This acts as an abstraction layer, enabling compatibility within the same family of CPUs, so that machine code written or generated according to the ISA for the family will run on all CPUs in the family, including future CPUs.

In general, each architecture family (e.g. x86, ARM) has its own ISA, and hence its own specific machine code language. There are exceptions, e.g. the IA-64 can emulate x86.

Machine code is a strictly numerical language, and is the lowest-level interface to the CPU intended for a programmer. There is, on some CPUs, a lower level interface in the form of (modifiable) microcode that implement the machine code. However, microcode is not intended to be changed by the end user on normal commercial CPUs. Assembly language provides a direct mapping between the numerical machine code and a human readable version where numerical opcodes and operands are replaced by readable strings (e.g. 0x90 is the NOP instruction on x86). While it is possible to write programs directly in machine code, managing individual bits and calculating numerical addresses and constants manually is tedious and error-prone. For this reason, programs are very rarely written directly in machine code in modern contexts, but may be done for low level debugging, program patching (especially when assembler source is not available) and assembly language disassembly.

The majority of practical programs today are written in higher-level languages or assembly language. The source code is then translated to executable machine code by utilities such as compilers, assemblers, and linkers, with the important exception of interpreted programs, which are not translated into machine code. However, the interpreter itself, which may be seen as an executor or processor performing the instructions of the source code, typically consists of directly executable machine code (generated from assembly or high-level language source code).

Machine code is by definition the lowest level of programming detail visible to the programmer, but internally many processors use microcode or optimise and transform machine code instructions into sequences of micro-ops. This is not generally considered to be a machine code.

Pronunciation examples for machine code
1. Everything was machine code.
The Friendly Orange Glow - The Untold Story of the PLATO System _ Brian Dear _ Talks at Google
2. He writes machine code and stuff just
Batkid Begins _ Patricia Wilson, Dana Nachman + More _ Talks at Google
3. And they then wrote code, usually machine code,
4. write with mixed machine code to make it work.
Morgan Freeman & Lori McCreary _ Madam Secretary _ Talks at Google
5. of the programmer and create automatically, machine code. She, 6 months later, produces
The Invention of the Information Age _ Kurt Beyer _ Talks at Google