Source : WordNet®

machine code
     n : a set of instructions coded so that the computer can use it
         directly without further translation [syn: {machine
         language}]

Source : Free On-Line Dictionary of Computing

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} {microprocessor}s) 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 {gate}s
        (e.g. to allow data to flow from main memory into a CPU
        {register}) and enabling {functional unit}s (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 {mnemonic}s (ASCII strings)
        for the "{op code}s" (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)