Processor

What do we mean by Processor?

Processor is the Brain of a computer.We also call it Central Processing Unit(CPU).The role of the CPU,is to control and direct all the activities of the computer using both external and internal buses.It is a processor chip consisting of an array of millions of transistors.The main two components of the CPU are the arithmetic logic unit(ALU),which performs arithmetic and logical operations,and the control unit(CU),which extracts instructions from memory and decodes and executes them,calling on the ALU when needed.

Operation:

The typical operation of most CPU's,consisting of their physical form,is to execute a sequence of stored instructions called a program.The program is represented by a series of numbers that are kept in some kind of memory called computer memory.There are  mainly four steps that a CPU use in his operation: Fetch, Decode, Execute and Write back.

Fetch, involves reacquiring an instruction from program memory.The location in program memory is determined by a Program Counter(PC),which stores a number that identifies the current position in the program.After fetching, the PC is incremented in terms of memory units.

The fetched instructions from memory is used to determine what the CPU has to do.In the Decode step,the instruction breaks into parts that have significance to other portions of the CPU.One group of numbers in the instructions indicate which operation to perform, and the other usually provide information required for that instruction.

In Execute step the portions of the CPU are connected so they can perform the required operation.The arithmetic logic unit(ALU) is connected to a set of inputs and outputs.The inputs accommodate the numbers to be added, and the outputs contain the final sum.The ALU performs arithmetic and logical operations.

The final step Writeback  is to write the results of the previous step to some form of memory.