Central Processing Unit

The CPU (Central Processing Unit) or processor is the component of digital computers that executes a series of instructions and data, known as programs.
It's probably the most important component of a computer.





The structure of a CPU is as follows:

o Control Unit (CU)
· controls sequences of instructions to be executed
· controls flow of data among all parts of the computer
· interprets instructions
· regulates the timing of the procressor
· sends and receives control signals from/to peripheral devices

o Arithmetic and Logic Unit (ALU)
· calculation
· logical comparsion and decision

o A number of Registers

· Program Counter (PC)
- holds the address of next instruction to be executed.

· Instruction Decoder
- interprets the instruction to be executed.

· Instruction Register (IR)
- holds the instruction being executed.

· Process Status Register
- it holds the "processor bit" about operations done by ALU.

· Accumulator (ACC)
- it stores intermediate and final results of calulation. It's the
main working area of the ALU.


· Memory Address Register (MAR)
- holds the address of the memory location where the next instruction is to be executed.

· Memory Data Register (MDR)
- contains the data to be stored in the computer storage (e.g. RAM), or the data after a fetch from the computer storage

· General Purpose Registers
- they can be used to store any temporary information during the execution of instructions.