Central Processing Unit

Introduction

• • The Central Processing Unit (CPU) is like the Brain of the computer. This is because it takes all major decisions, makes all sorts of calculations, and directs different parts of the computer functions by activating and controlling the operations.
  • The task of performing operations like arithmetic, logical, and non-logical/arithmetic operations is called Processing.
  • The CPU is a complex IC chip having millions of transistors.
  • The CPU or central processing unit takes data and instructions from the storage/ memory unit and makes all sorts of calculations based on the instructions given and the type of data provided. It is then sent back to the storage unit to store it.
  • To carry out the operations, the computer allocates the task among its various operational units i.e. arithmetic logical unit, control unit, and register.
  • The term CPU relates to a specific chip or processor.
  • The Central Processing Unit (CPU) is considered as one of the most important components of a computer system.
  • The fundamental operation of most CPUs is to execute a series of instructions called as a program.
  • The main function of a CPU is to execute a series of instructions called a program in a specific sequence. Normally there are four steps that all CPUs use to perform their operation these are: fetch, decode, execute, and output.
  • A dual-core processor has two cores, a quad-core processor contains four cores and a hexacore processor contains six cores on a single chip. Multi-core processors implement multi-processing which improves performance and speed of executions.
  • The different chip manufacturers use different measuring standards to measure the processor’s speed. It depends on the circuit board that the chip is housed in, or the motherboard. 
  • It is responsible for executing instructions.
  • It controls and coordinates the execution of instructions.
  • Execution of an instruction involves almost all parts (CU, ALU & Registers) of the CPU. Hence, the CPU is known as the most vital component of a computer system. 
  • CPU is mainly involved in the processing of input data. Processing the data thus means manipulation of letters, numbers, and symbols in a specific manner. The processing may include calculations, decision-making, comparisons, classification, sorting, aligning & formatting, etc. The processing of data results in some meaningful values/output, often termed as ‘information’.
  • As we know, a computer takes the raw data as input and performs several operations on these data in order to produce the desired output by the CPU so it acts as a processing unit for those data.
  • The CPU chip is connected with other components of the computer through a system bus (printed wires on the motherboard) which has three sets of wires forming the Control Bus, Data Bus, and Address Bus.

Features

• CPU is considered as the Brain of the computer.
• A CPU in a computer system is an extremely fast device as compared to the main memory, but it can not work on its own. It depends on the main memory to receive data and instructions when required for processing.

Function

• The central processing unit performs the bulk of the data processing operations i.e. CPU regulates the functioning of entire operations of the processor and memory along with input and output devices.
• In other words, it controls the activities of almost all functioning parts of the computer.

Components/Structure of CPU

• • The Processor is made up of registers, arithmetic & logic units, and control units.
  • A CPU is typically comprised of a Processor and Memory Unit i.e. (A) Control Unit (CU), (B) Arithmetic & Logic Unit (ALU) (C) Set of Registers (D) Memory Unit(MU) 

(A)Control Unit (CU) – 

Click this link to go to Control Unit details

(B)Arithmetic & Logic Unit (ALU)

• • These is the major components of the CPU.
  • The ALU is responsible for performing arithmetic as well as logical operations on data/signal as per given instructions. The CU, CPU registers, and memory help in bringing the data into the ALU and then taking the results back.
  • Data are presented to ALU in registers and the results are also stored in registers. The accumulator is one such register that is very frequently used during the ALU operation.
  • ALU has many other registers such as flags and status registers, which indicate information about the operation and its result.
  • ALU has logic implemented to perform operations like addition, multiplication, division, shifting, complement, etc. The operations are performed on represented numbers, both integer and floating point numbers.
  • Modern processors work in two ways which improve ALU performance to a much higher level. These are the use of on-chip Cache memory and having more than one processor core on the same IC chip. Here, Cache memory is a fast semiconductor memory that can be used to temporarily store instructions and data that are frequently referred by the processor thus, the wait cycles introduced due to memory references are minimized and hence the processor performance improves a lot. Another modern technique of having use of more than one processor core on the same IC chip tries to perform the execution of instructions in parallel and hence the performance of the processor improves a lot.
  • The co-processor or the arithmetic-logic unit does arithmetic, non-arithmetic, and logical operations.
  • The Arithmetic Logical Unit is an important component of the CPU, which carries the actual execution of the instructions.
  • The brief working mechanism of ALU is that after entering the data through the input device it is stored in the primary storage unit/RAM. Then processing of the data and instruction are performed by the Arithmetic Logical Unit. After that output is sent to the monitor screen to display or printer to print on paper as hard copy or hard disk to store it permanently via main memory or RAM.
  • The major operations performed by the ALU during processing are addition, subtraction, multiplication, division, logic, and comparison.
  • Data is transferred to ALU from the storage unit when required. After processing, the output is returned to the storage unit for further processing or storage.

(C) Registers/CPU Registers/Processor Memory

(For More Registers memory Details, Click this Link)

(D) Memory Unit(MU)

(For More Memory Unit Details, Click this Link)