The composition of a microprocessor

    The microprocessor consists of two main parts, the arithmetic unit and the controller.
    1. Arithmetic unit: It is the part of the computer that processes data. Its main functions include:
    (1) Performing arithmetic addition, subtraction, multiplication and division of numerical data, and performing logical operations such as AND, OR and NOT of logical data, which is completed by a circuit called ALU.
    (2) Temporarily storing the data and intermediate results involved in the operation, which is undertaken by multiple general registers.
    (3) The arithmetic unit is usually also the path for data transmission.
    2. Controller
    The part that controls the execution of instructions in the computer, and provides the control signals required for the coordinated operation of each functional component of the computer at every moment. Its main functions include:
    (1) Correctly executing each instruction: First, fetch an instruction, then analyze the instruction, and then execute the instruction according to the instruction format and function.
    (2) Ensure that instructions are automatically and continuously executed in the specified sequence.
    (3) Respond to and handle various abnormal situations and requests in a timely manner.
    3. Main registers in the CPU:
    (1) Accumulator (A): The most frequently used register, which cooperates with the ALU to perform various data processing. 
    (2) Data register (DR): It is a temporary storage unit that reads and writes data to the memory and I/O devices through the data bus.
    (3) Instruction register (IR): It temporarily stores the current instruction.
    (4) Instruction decoder (ID): It decodes each instruction into a control level.
    (5) Program counter (PC): It stores the current instruction address. When the CPU executes a program, it first fetches an instruction from the memory according to the address given by the PC, and the PC automatically increases by 1. After the CPU executes an instruction, it fetches the next instruction from the memory.
    (6) Address register (AR): It is used to save the address of the memory unit or I/O device that the current CPU wants to access.