**RG** Central Processing Unit (CPU) is the component of the computer running the computer programs. With memory in particular, it is one of the components that have existed since the first computers, a processor built into a single integrated circuit is a microprocessor. The processors were designed from the beginning specifically for a computer of a given type. This expensive method of processor design for a specific application has led to the development of mass production of processors that are suitable for one or more uses. This standardization trend that started in mainframes (discrete transistor mainframes and minicomputers) has accelerated rapidly with the advent of integrated circuits. Integrated circuits have enabled the miniaturization of processors. The miniaturization and standardization of CPUs have contributed to their dissemination in modern life far beyond the uses of programmable machines. While the complexity, size, construction, and the general form of CPUs have changed considerably over the last sixty years, the design and basic function has not changed much. Almost all common CPUs today can be described very precisely as machines of von Neumann's stored program. Composition of a processor The essential parts of a processor are: * Arithmetic Logic Unit (ALU), which supports basic arithmetic calculations and tests; * The control unit or sequencer, which synchronizes the various components of the processor. In particular, it initializes the registers when you start the machine and it handles interruptions; * Records, which are memories of small (few bytes), fast enough that the ALU can manipulate the content at each clock cycle. A number of records are common to most processors: - Meter: This register contains the memory address of the instruction being executed; - Accumulator: This register is used to store data being processed by the ALU; - Address register: it always contains the address of the next information to be read by the ALU, that is between the current instruction or the next instruction; - instruction register: contains the instruction being processed; Register state: it is used to store the context of the processor, which means that different bits of this register are the flags for storing information regarding the outcome of the last instruction executed; - stack pointers: this type of register, whose number varies depending on the processor type, contains the address of the stack(s); - general registers: These registers are available for calculations; * Clock that synchronizes all actions of the CPU. It is present in the processors, synchronous and asynchronous absent processors and processors Autosynchronous; * The unit input / output, which supports communication with the memory of the computer or the transmission of orders for its fly specialized processors, allowing the processor to access devices on the computer.