What Is Central Processing Unit (CPU)?

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  Category:  COMPUTER SCIENCE | 12th March 2024, Tuesday

The Central Processing Unit (CPU) Is The Primary Component Of A Computer System Responsible For Executing Instructions, Performing Calculations, And Coordinating The Activities Of Other Hardware Components. Often Referred To As The "brain" Of The Computer, The CPU Interprets And Carries Out Instructions Provided By Software Programs, Enabling The Computer To Perform A Wide Range Of Tasks.

The Central Processing Unit (CPU) Serves As The Brain Of A Computer System, Responsible For Executing Instructions, Performing Calculations, And Managing Data Processing Tasks. Here's An Overview Of Its Key Components And Functions:

1. Control Unit (CU):

   • The Control Unit Directs The Operation Of The CPU And Coordinates The Execution Of Instructions.
   • It Fetches Instructions From Memory, Decodes Them, And Controls The Execution Of The Appropriate Operations.

2. Arithmetic Logic Unit (ALU):

   • The Arithmetic Logic Unit Performs Arithmetic Operations (such As Addition, Subtraction, Multiplication, And Division) And Logical Operations (such As AND, OR, And NOT) On Data.
   • It Processes Binary Data According To The Instructions Provided By The Control Unit.

3. Registers:

   • Registers Are Small, High-speed Storage Units Located Within The CPU.
   • They Temporarily Hold Data, Instructions, And Memory Addresses During Processing.
   • Common Types Of Registers Include The Instruction Register (IR), Program Counter (PC), Accumulator, And General-purpose Registers.

4. Clock Speed:

   • The Clock Speed, Measured In Gigahertz (GHz), Determines How Quickly The CPU Can Execute Instructions.
   • It Represents The Number Of Cycles Per Second That The CPU Can Process.
   • Higher Clock Speeds Generally Result In Faster Performance, But Other Factors Such As Architecture And Efficiency Also Play A Role.

5. Cache Memory:

   • Cache Memory Is A Small, High-speed Memory Unit Located Within Or Near The CPU.
   • It Stores Frequently Accessed Data And Instructions To Reduce Latency And Improve Performance.
   • The Cache Hierarchy Typically Includes Levels Such As L1, L2, And L3 Caches, With Decreasing Size And Increasing Latency.

6. Instruction Pipeline:

   • The Instruction Pipeline Allows The CPU To Execute Multiple Instructions Simultaneously, Overlapping Different Stages Of Instruction Processing.
   • It Improves Throughput And Efficiency By Dividing Instruction Execution Into Sequential Stages, Such As Fetch, Decode, Execute, And Write Back.

7. Instruction Set Architecture (ISA):

   • The Instruction Set Architecture Defines The Set Of Instructions That The CPU Can Execute And The Format Of Those Instructions.
   • It Determines The CPU's Capabilities, Instruction Formats, Addressing Modes, And Supported Data Types.

8. Multicore Processors:

   • Multicore Processors Contain Multiple CPU Cores On A Single Chip, Allowing For Parallel Execution Of Instructions.
   • Each Core Operates Independently And Can Execute Its Own Set Of Instructions, Improving Overall Performance And Multitasking Capabilities.

9. Floating-Point Unit (FPU):

   • The Floating-Point Unit Handles Floating-point Arithmetic Operations, Such As Addition, Subtraction, Multiplication, And Division, On Numbers With Fractional Components.
   • It Is Often Integrated Into The CPU Or Provided As A Separate Coprocessor.

Overall, The CPU Plays A Central Role In Computer Systems, Executing Instructions, Performing Calculations, And Managing Data Processing Tasks To Enable The Functionality Of Software Applications And The Overall Operation Of The System.

Control Unit (CU)

The Control Unit Manages The Instructions Given To The Computer. It Coordinates The Activities Of All The Other Units In The System By Instructing Rest Of The Components Of The Computer About How To Carry Out A Program’s Instructions. It
reads And Interprets Instructions From Memory And Transforms Them In To Series Of Signals To Be Executed Or Stored. It Also Directs The Movement Of These Electronic Signals Between Memory And ALU Or Between CPU And Input/output Devices.

Hence It Controls The Transfer Of Data And Information Between Various Units. The User’s Program Provides The Basic Control Instructions. Conceptually, The Control Unit Fetches Instructions From The Memory, Decodes Them And Directs The Various Units To Perform The Specified Functions.

Arithmetic Logic Unit (ALU)

Arithmetic Logic Unit Or ALU Performs Two Types Of Operations - Arithmetic And Logical. Arithmetic Operations Are The Fundamental Mathematical Operations Consisting Of Addition, Subtraction, Multiplication And Shifting Operations. Logical Operations Consist Of Boolean Comparisons Such As AND, OR And NOT.

Memory Registers

The CPU Processes Data And Instruction With High Speed. There Is Also Movement Of Data Between Various Units Of The Computer. It Is Necessary To Transfer The Processed Data With High Speed. So The Computer Uses A Number Of Special Memory Units Called Registers. A Memory Register Is A Sort Of Special Storage Area  That Holds The Data And Instructions Temporarily During Processing. Since This Is Internally Located In The CPU, The Processing Time Is Very Less. They Often Hold Data For Less Than A Millisecond. This High Speed Storage Area Make Processing More Efficient.

To Locate The Characters Of Data Or Instructions In The Main Memory, The Computer Stores Them In Locations Known As Addresses. A Unique Number Designates Each Address. Addresses Can Be Compared To Post Office Mailboxes. Their Numbers Remain The Same, But Contents Continuously Change.

The Contents Of The Memory Are Held Only Temporarily, That Is, It Is Stored Only As Long As The Microcomputer Is Turned On. When You Turn The Machine Off, The Contents Are Lost. The Capacity Of The Memory To Hold Data And Program Instructions Varies In Different Computers. The Original IBM PC Could Hold Approximately Several Thousand Characters Of Data Or Instructions Only. But Modern Microcomputers Can Hold Millions Or Even Billions Of Characters In Their Memory.

How The CPU And Memory Work Together?

The CPU And Memory Work Together Closely To Execute Instructions, Process Data, And Manage The Overall Operation Of A Computer System.

Here's How They Collaborate:

1. Instruction Fetch: The CPU Retrieves Instructions From Memory, Typically From The Main System Memory (RAM). The Control Unit (CU) Sends Memory Addresses To The Memory Controller, Which Retrieves The Corresponding Instructions From RAM And Sends Them To The CPU.

2. Instruction Decode: The CPU's Control Unit Decodes The Fetched Instructions To Determine The Operations To Be Performed. It Interprets The Instruction's Opcode (operation Code) And Determines The Required Operands And The Type Of Operation (arithmetic, Logical, Data Transfer, Etc.).

3. Data Fetch: If The Instruction Involves Accessing Data From Memory, The CPU Requests The Required Data From Memory Using Memory Addresses Provided By The Instruction. The Memory Controller Retrieves The Data From RAM And Sends It To The CPU For Processing.

4. Execution: The Arithmetic Logic Unit (ALU) Performs The Necessary Arithmetic Or Logical Operations On The Data Fetched From Memory Or Stored In Registers. The ALU Carries Out Calculations, Comparisons, And Other Manipulations Based On The Decoded Instructions.

5. Write Back: After Executing The Instruction, The CPU May Need To Write The Results Back To Memory. This Involves Sending The Updated Data Or Computation Results To The Appropriate Memory Location In RAM, Where They Can Be Stored For Later Use Or Accessed By Other Components.

6. Cache Memory: In Addition To Accessing Main System Memory (RAM), The CPU May Utilize Cache Memory To Store Frequently Accessed Data And Instructions. Cache Memory Is Faster Than RAM And Helps Reduce The Time Required For The CPU To Fetch Data And Instructions, Thereby Improving Overall Performance.

7. Memory Hierarchy: The CPU And Memory Operate Within A Hierarchy Of Memory Levels, Including Registers, Cache Memory (L1, L2, L3), And Main System Memory (RAM). Each Level Of The Memory Hierarchy Offers Different Speeds, Capacities, And Costs, With Registers Being The Fastest But Smallest And Most Expensive, And RAM Being Slower But Larger And More Affordable.

Overall, The CPU And Memory Work In Tandem To Execute Instructions, Process Data, And Manage The Flow Of Information Within A Computer System. Their Collaboration Is Essential For The Smooth And Efficient Operation Of The System, Enabling It To Perform A Wide Range Of Computing Tasks.

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CPU, Central Processing Unit, What Is Cpu?