1. General structure of CPU:
The CPU is the brain of a computer. Its primary function is to ***/run the programs. Under its control, programs and data are stored in the memory and displayed on the monitor (CRT screen) or printed on the printer. The CPU consists of Arithmetic and Logic unit, Timing and Control Unit, Accumulator, General, and special-purpose registers.
2. Program Counter Register (PC):
The PC points to memory location that holds the next instruction to be ****;
3. Memory Address Register (MAR):
it holds address of the active memory location loaded from the program counter register. The CPU transfers the instruction location from PC to MAR. From MAR it is sent to the memory through the address bus.
4. Memory Buffer Register (MBR) or Memory Data Register (MDR):
It contains data of memory location specified by MAR for the purpose of storing or to retrieve. It is connected to data bus. The flow of data from the CPU to the memory or from the memory to CPU is always through MBR.
5. Arithmetic and Logic Unit (ALU):
The function of an ALU is to perform arithmetic operations such as +, -, *, /, ^ and logic operations such as AND, OR, NOT, ++, —, >, >=, <, <=, != (not equal) etc.,
6. Accumulator Register (AR):
The accumulator usually stores one of the operands to be manipulated by the ALU. The accumulator is an 8-bit register. It holds one of the operands to be operated on by the ALU and receives the result of an operation done by the ALU. In general, the accumulator is both a source (operand) and a destination (result) register.
7. Instruction Register (IR):
It holds the instruction currently being **** and until decoded. It separates the operation part of instruction and is sent to the control unit and the address part is sent to MAR of the instruction.
8. Instruction Decoder (ID):
It is electronic hardware, which decodes the instruction and they are further divided into a set of micro-operations.
9. Timing and Control Unit (TCU):
It generates timing and control signals necessary for the ***** of instructions. It provides status, control and timing signals necessary for the operation of other parts of the CPU, memory and I/O devices. It controls the entire operation of the computer.
