Machine code

Machine language — a command set of the specific computer which is interpreted at the hardware level or using microprograms of the machine.

Each model of the processor has an own machine language though in many models these command sets are strongly blocked. They say that processor A is compatible to processor B if processor A completely "understands" machine code of processor B. If processor A knows several commands which does not understand processor B, then B is incompatible with A.

"Words" of a machine language are called machine instructions. Each of them describes the elementary operation performed by the processor such as "send byte from memory to the register". The program is just long list of the instructions which are carried out by the processor. Earlier processors just carried out instructions one for another, but new superscalar processors are capable to carry out several instructions for time. The direct execution thread of commands can be changed by the instruction of transition which transfers accomplishment to the instruction with the set address. The instruction of transition can be conditional, executing transition only at observance of some condition.

Also instructions are constant length (at RISC, MISC architecture) and band (at CISC architecture; for example, for architecture of x86 the command has length from 8 to 120 bits).