machine code

In computing, a set of instructions that a computer's central processing unit (CPU) can understand and obey directly, without any translation. Each type of CPU has its own machine code. Because machine-code programs consist entirely of binary digits (bits), most programmers write their programs in an easy-to-use high-level language. A high-level program must be translated into machine code – by means of a compiler or interpreter program – before it can be executed by a computer.

Where no suitable high-level language exists or where very efficient machine code is required, programmers may choose to write programs in a low-level, or assembly, language, which is eventually translated into machine code by means of an assembler program.

Microprocessors (CPUs based on a single integrated circuit) may be classified according to the number of machine-code instructions that they are capable of obeying: CISC (complex instruction set computer) microprocessors support up to 200 instructions, whereas RISC (reduced instruction set computer) microprocessors support far fewer instructions but execute programs more rapidly.