What is Hub, Bridge, Router & Switch in Networking?

Everyone is use all of them in general life but we don't know how they works and what is the difference between hub bridges etc so lets discuss all of them.

Hubs

Hubs and switches serve as a central connection for all of your network equipment and handles a data type known as frames. Frames carry your data. When a frame is received, it is amplified and then transmitted on to the port of the destination PC

Hub Icon
Image: Hub and wireless hub network icons

In a hub, a frame is passed along or “broadcast” to every one of its ports. It doesn’t matter that the frame is only destined for one port. The hub has no way of distinguishing which port a frame should be sent to. Passing it along to every port ensures that it will reach its intended destination. This places a lot of traffic on the network and can lead to poor network response times

A hub is a physical layer networking device which is used to connect multiple devices in a network. They are generally used to connect computers in a LAN.

A hub has many ports in it. A computer which intends to be connected to the network is plugged in to one of these ports. When a data frame arrives at a port, it is broadcast to every other port, without considering whether it is destined for a particular destination or not.

Usage:-

Now suppose that your office issues you a laptop, and you want to be able to telecommute (work from home) at times. Because you already have an Internet connection to your home, you might want to share that connection, rather than install a second connection for your laptop; a small hub enables you share this connection, as illustrated in Figure.

Bridge

A bridge in a computer network is one kind of network device, used to separate a network into sections.

Every section in the network represents a collision domain that has separate bandwidth. So that network performance can be improved using a bridge. In the OSI model, a bridge works at layer-2 namely the data link layer. The main function of this is to examine the incoming traffic and examine whether to filter it or forward it.

Working Principle

The working principle of a bridge is, it blocks or forwards the data depending on the destination MAC address and this address is written into every data frame.

Bridge-in-Computer-Network — bridge-in-computer-network

In a computer network, a bridge separates a LAN into different segments like segment1 & segment2, etc and the MAC address of all the PCs can be stored into the table. For instance, PC1 transmits the data to PC2, where the data will transmit to the bridge first. So the bridge reads the MAC address & decides whether to transmit the data to segment1 or segment2. Therefore, the PC2 is accessible in segment1, which means the bridge transmits the data in segment1 only & eliminates all the connected PCs in segment2. In this way, the bridge reduces traffic in a computer network.

Types of Bridges

Transparent Bridge

Translational Bridge

Source-route Bridge

Functions of Bridges in Network

Advantages/Disadvantages of Bridge in Computer Network

The advantages are

It acts as a repeater to extend a network
Network traffic on a segment can be reduced by subdividing it into network communications
Collisions can be reduced.
Some types of bridges connect the networks with the help of architectures & types of media.
Bridges increase the available bandwidth to individual nodes because fewer network nodes share a collision domain
It avoids waste BW (bandwidth)
The length of the network can be increased.
Connects different segments of network transmission

The disadvantages are

It is unable to read specific IP addresses because they are more troubled with the MAC addresses.
They cannot help while building the network between the different architectures of networks.
It transfers all kinds of broadcast messages, so they are incapable to stop the scope of messages.
These are expensive as we compare with repeaters
It doesn’t handle more variable & complex data load which occurs from WAN.

Router

Routers are networking devices operating at layer 3 or a network layer of the OSI model.

They are responsible for receiving, analysing, and forwarding data packets among the connected computer networks. When a data packet arrives, the router inspects the destination address, consults its routing tables to decide the optimal route and then transfers the packet along this route.

Features of Routers

A router is a layer 3 or network layer device.
It connects different networks together and sends data packets from one network to another.
A router can be used both in LANs (Local Area Networks) and WANs (Wide Area Networks).
It transfers data in the form of IP packets. In order to transmit data, it uses IP address mentioned in the destination field of the IP packet.
Routers have a routing table in it that is refreshed periodically according to the changes in the network. In order to transmit data packets, it consults the table and uses a routing protocol.
In order to prepare or refresh the routing table, routers share information among each other.
Routers provide protection against broadcast storms.
Routers are more expensive than other networking devices like hubs,bridges and switches.

Routing Table

The functioning of a router depends largely upon the routing table stored in it. The routing table stores the available routes for all destinations. The router consults the routing table to determine the optimal route through which the data packets can be sent.

A routing table typically contains the following entities −

IP addresses and subnet mask of the nodes in the network
IP addresses of the routers in the network
Interface information among the network devices and channels

Routing tables are of two types −

Static Routing Table − Here, the routes are fed manually and are not refreshed automatically. It is suitable for small networks containing 2-3 routers.
Dynamic Routing Table − Here, the router communicates with other routers using routing protocols to determine the available routes. It is suited for larger networks having large number of routers.

Difference b/w Switch and Hub

What is a Switch?

A network switch is a computer networking device that connects various devices together on a single computer network. It may also be used to route information in the form of electronic data sent over networks. Since the process of linking network segments is also called bridging, switches are usually referred to as bridging devices.

What is Hub?

A Hub is a networking device that allows you to connect multiple PCs to a single network. It is used to connect segments of a LAN. A hub stores various ports, so when a packet arrives at one port, it is copied to various other ports. Hub works as a common connection point for devices in a network.

Thanks For Reading

Shivanshu Tiwari

File Management:-

what is file management :-This part is most important part of the window . it is use to handle the file , creating new ,editing deleting etc.This is useful not useful not only file but directory also called folder management by opening window Explorer window you can create a new file or folder , or delete selected file/folder.You can also create copy the selected file and posts for another file.

File:-

A file is a container which contains some specific kind of data or important . A file is built by the system itself or by a user for his/her own purpose . A file has always two segment -first one is the file name and second one is File Extension and both are separated using dot(.) character . A file name is used or kept to search and use it easily whereas the the file extension is used to the tell the type of the file.

here we see some example of file extension of a file created by a user .doc ,.docx,.txt,.bmp,.xls,.xlsx,.ppt,.pptx,.htmp etc.and some example of a file extension created by the system .dll,msc,.sys,.zip,.exe,.ini etc.

Using essential accessories

There is a number of essential accessories in the computer system comes with the operating system package in default like paint, Notepad,World pad, calculator,etc Here comes the details those follows:-

System tools:=

system tools are the built in tool command which are used is system management and configuration related to disk management ,disk Defragmentation etc.

Disk cleanup:-

Disk Cleanup is used to free up space on your hard disk , Disk Cleanup finds and then removes temporary files on your computer that you decide you no longer need. If you have more than one drive or partition on your computer ,you will be promoted to choose which drive you want Disk Cleanup to clean.

Here is the step to conduct a Disk Cleanup.

👉.Click start button and go to Accessories and then.

👉 Goto System tool and choose Disk cleanup.

👉 This will prompt you select a partition if there is more than one partition.

Select the partition and click OK;and you will see a dialog containing lift of unnecessary files to be cleaned by deleting files.

👉 Check to select for cleaning those from the computer system and click OK

Disk Defragmenter:-

Fragmentation makes your hard disk do extra work that can slow down your computer . Removable

storage device such as USB drivers can also become fragmented . Disk Defragmenter rearrange fragmented data so your disk and drivers can work more efficiency .Disk Defragmenter runs on a schedule ,but you can also analyze and defragment your disk and drive.

👉Click Defragment disk, if you sre prompted for an administrator password or confirmation ,type the password or provide confirmation .

Disk Defragmenter might take from several min to a few hours to finish . depending on the size and degree of fragmentation on your HDD ,you can still use your computer during defragmentation process.

Clean Temp File:-

Programs often store temporary files on your hard drive. Over time, these files can start to take up a lot of space. If you are running low on hard drive space, clearing temporary files is a good way to reclaim additional disk storage space.

Click any image for a full-size version.

Press the Windows Button + R to open the "Run" dialog box.
Enter this text:
%temp%

👉 Click "OK." This will open your temp folder.

👉 Press Ctrl + A to select all.
👉 Press "Delete" on your keyboard and click "Yes" to confirm.

Prefetch:-

Prefetch files are automatically created to speed up the launch of certain applications and don't usually take up much space on your drive. There's no real reason to delete these files unless you need to free up a small amount of space

👉Press win+R to open RUN Dialog Box.

👉Type Prefetch in to the Run box and Hit enter(OK).

👉CTRL+A select all file and hit cmd SHIFT+DELETE and hit eneter.

Now check your c drive and stay happy ...

Temp File:-

A file created by an application for its own purposes. In the days of limited main memory, temporary files were the only way to store large amounts of interim data that the application was generating. Today, main memory is often used instead. Temporary files typically have a .TMP or .TEMP file extension, but any naming convention might be used.

Not Always Deleted

An application is responsible for deleting its temporary files; however, such files often remain on disk if the computer crashed, and the program was not closed properly. See temporary folder and temporary internal file

THANKS YOUR READING

SHIVANSHU TIWARI(SSKKT)

What is CPU Register:-

Register is a temporary storage memory that is built into Processor(CPU). In the Computer Architecture, registers are special types of computer memory which are performed their tasks quickly such as (Fetching, transferring, and storing) data and instructions.

These are the high speed memory location built into the microprocessor.Register small areas of extremely fast storage
usually measured by the no of bits they hold e.g._a "32 bit register or a ""64 bit register".

x86 architecture provide 16 basic program register:

General Purpose Register (EAX,EBX,ECX,EDX,ESL,ESL,EBP,ESP,)
Segment Register(CS,DS,SS,ES,FS,GS,EFLAG,EIP)

X64 ADDRESS an additional 8 general purpose register:

RAX, RBX, R CX, RDX, RDL, RSL ,RBP ,RSP ,R8-R15.

The cpu usages these location to store data and instruction temporarily for pro
cpu process , store and transfer data from one components to another with the help of register .
The number of register variable among computers.
it increases the performance of cpu.
Each register receive the information , holds the temporarily and pass it on, as direct by CU
the size of register depend on the computer architeture..

PC(Program Counter)

IR(Instruction register)

MAR (Memory Address Register)

IP(Instruction Pointer)

SPR(Stack Pointer Register(SP)

GPR (General Purpose Register)(A,B,C,D)

Address and Segment Register(CS,DS,ES,SS)

Index Register(Dl , Sl)

PC(Program counter):_

1. it holds the add of the next instruction to be fetched and executed .
2. when instruction is fetched the value us automatically incremented and its points to the add of next instruction.

IR(Instruction Register):-

it holds the current instruction that is being executed.

MAR Register

MAR stand for “Memory Address Register”, and its main objective is to store all memory addresses of entire data and instructions.MAR helps to make the communication with using of MDR (Memory Data Register) in between the CPU and Main Memory

MBR(Memory Buffer Register):-

it holds the content of memory location read from or written in the memory.

FR Register

FR register stands for “Flag Register“, and this register helps to indicate the specific condition. Flag register contains the one or two bytes, and further every byte is splitted into 8 bits. And every bit delivers the flag means condition.

Few flags register are Carry flag, Parity flag, Sign flag, Zero flags, and Overflow flag.

GPR Registers

GPR stands for “General Purpose Registers“, and these are unified types of registers. These registers are capable to store the memory addresses, data values as well as floating-point values. Mostly, GPR registers are used into modern CPU and GPUs due to their best flexibility.

SPR Register

SPR stands for “Special Purpose Registers“, and they are used to hold the program state. SPR registers are enabled with PC (Program Counter) and SR (Status Register).

General Purpose Register:-

These register are used to perform arithmetic and logical operation

EAX, EBX, EDX, are 4 byte register AX, BX, CX and DX are 2byte AH ,AL BH,BL,CH,CL,DH and DL are 1 byte register.

AX(Accumulator Register)

it is used to asthmatic and logical operation,it holds the initial data to be operated upon and the final result for processing .
the result of arithmetic operation are returned to accumulator to transfer to the main memory through buffer.
BX(Base Register)
it is an address register that can be used for in directing addressing.
CX(counter Register)
it is used for counting purpose,it acts as counter loop ex .for(int i=10;i>0;i--)
DX(Data Register)
it is special role in division and multiplication.

Segment Register / Address Register:

it is a group of four segment CS,DS,ES,SS.
size of each segment register is 2 byte.
CS(Code Segment)
it hold the base location of all executable instruction in the program .CS along with ip register fetches the next instruction.
DS(Data Register)
it is default base location for memory variable.
DS points of data in memory using Dl and SI
CPU calculate the offset variable using the values of DS.
ES(Extra Segment)
it is additional base location for memory of DS .
SS(Stack Segment):
it contains the base location of the current program stack.

Index Register:
index Registry are used for data movement.
there are two type of index registers.
SI(Source Index)
DI(Destination Index
DS Point to data in memory using DI (destination index) or SI(source Index) registes.

IP(Instruction Pointer)
CS along with ip Register fetched the next instruction.

THANKS FOR READING

SHIVASNHU TIWARI

WHAT IS ANTIVIRUS

Anti Virus:-

it is interesting to node that the arrive of the computer virus generate a whole cub-industry of software development concentrating on providing software antivirus tool to the user . it is also interesting to node that most user prefer to think that it is the antivirus guys whole themselves crate and release viruses. After all, a

in fact, most antivirus personnel know perfectly how harmful a virus is,and the potential for damage involved ,and would refrain from doing any such thing,However industry has its black sheep and it is indeed possible that all antivirus personnel may not have the same high moral standard ,Most antivirus personnel have accumulated may not specialized knowledge about antivirus .So they admittedly have the knowledge to churn out highly complicated virus.

What is antivirus software designed to do?

What exactly is antivirus software designed to do? We’re talking about a program or umbrella of programs whose purpose is to scan for and eradicate computer viruses and other malicious software, also known as malware. Antivirus software is a vital component of your overall online and computer security strategy in its protection against data and security breaches along with other threats.

Free antivirus software: Does it work?

Another common question is whether free antivirus software protects us. But is anything ever really free? “Free” antivirus inevitably supports and makes money with advertising and tracking, and by installing junkware.

Free downloads also can hide malware. If you go this route, only download software from sites that you absolutely trust. You also must ensure that your security setting is set high enough to detect malicious codes.

Another thing to keep in mind when considering whether to rely on free antivirus protection? Identity theft protection, mobile security, and data security support options. These important security features often are lacking with free software.

PREVENTERS AND CHECK-SUMMERS:-

one category of antivirus program deals with preventing the virus from entering the system . The notion is that if that if the system can not be infected ,virus will never spread .These preventor work either by scanning for specific viruses signature during program execution or by looking for virus like behavior . While the benefit of having a preventor is unquestionable ..

Most of the antivirus package come along with a prevention program that is cable of defecting the virus before the system infected . for ex:-Na-shot Antivirus package comes with the "NashMen" prevent-or.

Checksummer are used to report the change in content of executable file in the system.When a new virus infect the system ,it has to necessarily make modification either to the system area(boot/partition sector) or to the executable files present in the system. The checksummer keeps track of a checksum or CRC(cyclic Redundancy Check) associate with each exe file and informs the user when a change happen.

SCANNERS:-

scanners program check for the presence of virus signature either in memory of program file and can tell you if your system in infected or not. Most scanner perform both a memory and a file scan .Scanners do not remove virus ,they merely report the presence of the infection.As a result ,some antivirus companies give away their scanning software as freeware ,so that the user would be able to evaluate the product ,Of course ,if you want to remove an infection ,you will have to boy the product.

Most scanner merely check for the presence of the virus signature in the files .Some scanner also include heuristic scanning -which is also capable of ducting most new viruses .However ,all scanner which support the heuristic method of scanning also pop up a warning message about possible midsection.

REMOVERS:-

if any computer system is affected by virus then there are remedies to wash off the virus .These are special computer program or software which are used to detected virus by scanning the whole system ,and later repairing it by removing the viruses .These are called anti virus program.

the most popular antivirus program is NORTAN ANTI VIRUS or NAV in short.

it is a very powerfull software which can detect and remove almost every kind of computer virus. it can also check the virus from the internet through e-mail.if this anti virus is executeed with the booting and kept remains executing till the computer is on, it check the virus from being executed as and when a file a recevied .it filter all incoming file through e-mail to stop them entering computer system.

TROJAN:-

A Trojan horse or Trojan is a type of malware that is often disguised as legitimate software. Trojans can be employed by cyber-thieves and hackers trying to gain access to users' systems. Users are typically tricked by some form of social engineering into loading and executing Trojans on their systems. Once activated, Trojans can enable cyber-criminals to spy on you, steal your sensitive data, and gain backdoor access to your system. These actions can include:

⇨Deleting data
⇨Blocking data
⇨Modifying data
⇨Copying data

zombies:-

They are program that isntall themselves on computers are remain dormant until some event them into action .The action could include corrupting,truncating ,or stealing your info and sending it to a predefined email account or opening up remote control access ports

if you have any problem about this pls contact shivanshut9889@gmail.com

Thanks for Reading

SHIVANSHU TIWARI

What is virus:-

The name is enough to scare any user . No computer in the world is protect from virus .Virus infect the computer in many ways and are various types. There are many program to stop them . This chapter will deal with information about virus in details.

Usually when we comes across the term virus we are mistake of the virus we suffer from and get ill with flu and like that . It is actually not.Virus in term of computer is not a living organism which affects our body.A computer virus ,in real , is a tiny program which when enters a computer ,gets associated with pre-install program and application and induces malfunction the program.

The computer virus (a program) when enters the computer destructs the proper working of a computer .it can affect working of a computer ,

⟹ by destroying important information in the computer.

⟹ by making change in the directories

⟹ by formatting floppy and HDD

⟹ by diminishing the speed of the computer processing

⟹ by altering the function of the keys on keyword

⟹ by hindering the booting of a computer

⟹ by altering the size and structure of life

⟹ by stopping or hindering the execution of file

When a virus affected program is executed ,the virus executes itself in the primary memory of the computer.

How virus work:

It is computer program which can duplicate itself. But ,since virus is a computer program it too has its limits ,Virus can do as much as it has been instructed by the programmer through program . for example , a Michael Angelo virus destroys data on march 6 as the programmer has instructed is to ensure ,first,it is 6 march and if he ascertain and if he ascertain that it is 6 march it displace the disk sector.
We also know that no command can be executed themselves .till we issue such as an instruction, Likewise a virus program is either executed directly by the user or when another program is executed by the user .Now the question is why a user will execute a virus on his own computer .for it,virus creator use technique so that the user can be fooled to execute virus .In most of the situation ,virus are present in already .exe file .when file is executed the virus code too are executed.
Usually the virus program gradually start copying themselves in other exe files; and when these file are executed by the user then they start spreading on the entire system.

Reason:-

Using pirated software:-

when user acquire a program illegally it is called a pirated software .A pirated software has max portability to be infected from virus as it comes from unauthentic sources and whenever the pirated software are used,they carry viruses.

Through Network System:-

on the network when gets affected and it is shared with other clients than this cause infection spread among all the shared clits.

Through Secondary Storage Device:-

When a file is copied from a virus affected computer through secondary storage device , virus also gets communicated to that very system.

Through Internet:-

internet is supposed to the most critical carries of viruses.

Types Of Computer Virus:-

Virus can be classified into many categories .They are classified as follow on the basis of their style of affecting the computer system.

Boot sector Virus:-

these type of computer virus get themselves stored in the boot sector or floppy and hard disk .When we boot a computer system it hinders the loading of operating system . if somehow operating system becomes operative , then it start affecting the other device of the computer.

Partition Table Virus:-

these kind of virus affect the partition table of hard disk but do not affect the data in the computer

It only affect MBR -Master Boot Record of the HDD which may have following

This virus executes itself on the high priority place in MBR.
It decrease the capacity of RAM.
it affect the I/O stream of disk which leads to the malfunctioning of I/O program.

File Virus:-

this kind of virus gets associated with exe file . When an EXE file is executed , virus also executed to affect the computer system.

Stealth Virus:-

a Stealth virus is a computer virus that makes every effort to conceal its presence from the user . The techniques range from hiding the increasing the increase in size of an infected file from the user , all the way to infecting the disk in multiple areas so the simply removing the infection from one area does not actually remove the virus.

Polymorphic Virus:-

A polymorphic virus is one that is capable of changing itself so that each infection of the virus is completely different from the original it is very difficult to check such virus since every time they are completely different.

Macro Virus:-

It is type of file such as documents file and spreadsheet file. Micro virus designed as macro ( a special program contain set of command for execution of a particular task in the very software ), can damage data when used

Thanks For Reading .

Mercury

Central Processing Unit(CPU)

What is Central Processing Unit(CPU), CPU an acronym for Central Processing Unit , supposed to be the brain of computer it mainly executes the program and controls different parts of a computer such as memory , input and output devices. Program and data are stored under its control . It helps you see your output on the screen and gets print out on the paper through printer.

The Processing device are central processing unit (CPU);also called microprocessor chip in computer which receive input and provide output . It composed of silicon & contains of transistor for e.g. Pentium dual core,Core 2 Duo,Core i3. i5, i7 etc.

Central processing Unit include mainly 3 parts , they are as follows:

Arithmetic & Logic Unit
Main Memory Unit
Control Unit

WHAT DOES A CPU LOOK LIKE?

It’s basically a silicon chip in the shape of a square or rectangle with millions of microscopic transistors. On the bottom and backside are hundreds of short, rounded, metallic connector pins

Arithmetic Logic Unit:

Arithmetic Logic Unit is Know as A.L.U. in shorts . This unit performs mathematical operations as well as logical operation on data . It contain an electronic circuit . That can do calculation like add,multiplication become multiple times addition and later gets transmitted after converting them into electrical Pulses .

In Logical operation ,A.L.U. Compare two no and data makes decision while processing,

A.L.U. takes instruction or guidelines from control unit . it gets data from memory and return information to the same A.L.U. works amazingly fast , its estimate speed is about 1 million+ calculation per second it contains several register and accumulator which works as virtual memory during calculation A.L.U. ., as instructed by the control unit according to be programs receive data from memory and place them on accumulator.

for ex, you are add two no A&B . control unit select a from memory and add to B available in A.L.U. output gets in memory or for future calculation it is stored in accumulator .

Control Unit:

Decode instruction and determine which next to be executed . Control unit is a part of the processor that is in-charge and it direct the computer system to execute stored program instruction . It communication with other parts of the hardware.

Control Unit is a internal process of a computer . It controls the input and output process of the computer . It also direct the exchange of data and instruction between memory & ALU

It received the instruction of a program to execute the program itself from memory. Then it convert the instruction into electronic signal and delivers them to the appropriate device to complete the data processing . Control unit also direct the ALU about the location of the data processed in the memory . The control unit also instruct the ALU about what operation to be performed , and after processing , where to the store the output. the instruction in the form of signal are sent to various parts of computer through the control bus carrier electronic signal through out the system unit . they are named on the basis of the type of signal they carry. the main bus of the system unit is called system bus . And the BUS used for the transportation of control signal is called control BUS.

Registers:

Computer instruction are carried out the C.P.U. to execute instruction , information is exchanged C.P.U. of computer uses a memory unit to exchange information fast and sanctification . This memory unit is called a register.In memory unit data are stored during the processing. Its speed is faster access then memory formally we call this Register too.

Register are not a part of main memory . They store information for time being . Size of a register equals to the capacity of its storage of bit . For instance , If a register can store 8-bits then it is called 8 bit register . Nowadays 16-bit register are in vogue while 32 bit and 64 bit processor are also in use. the more bit register would have , the faster data processing of computer will be, computer has got following type register:

➱ Memory Address Register:

This store active memory location of computer instruction.

➱ Memory Buffer Register:

This register store the content read from to write onto memory.

➱ Program Control Register:

This stored address of the instruction to be execute next.

➱Accumulator Register:

This Register stored the middle and last result of the data being execute Normally . these register are used while execution of information.

➱Instruction Register:

These register store instruction to be executed.

➱ Input/Output Register:

These register are used to communicate info between input or output device.

BUS:

Let us discuss what is BUS is. it acts like a path between the components of computer a computer has two main buses , First Internal OR system bus and second external or expansion bus . The system bus is situated on the motherboard and links the CPU with other device on the motherboards .The task of expansion has BUS is to link the CPU with external device for ex key-boards ,mouse,modern,printer etc.The chords of disk drive and other device are plugged in the bus . The system bus has two parts -DATA BUS & ADDRESS BUS . Data bus is an electrical path which attaches , CPU , memory and other hardware device . in fact , a bus is a set of parallel chords.The number of chords in the bus affects the transaction of data between hardware components .Because every chords can transfer 1 bite of data at a time . one eight chords bus can carry eight bite . It means one byte at a time.Address bus too is a set of chords like data bus ,An address bus links only a CPU and RAM and carries memory address only , every byte in the ram is attached to a number which is its memory address.

Instruction Set:

Let us see what an instruction set is. Every process accomplishes takes like receiving character from the memory or getting a large number after comparing between two number .All of these operation have their own number which are called instruction . The list of instruction in processor is called instruction set . Each processor in mind.

C.P.U. instruction which are for executing are prepared in a control unit instruction or instruction set list such operation that C.P.U can perform . Each instruction of instruction set represented in micro codes that instruct C.P.U about how to carry out complex operation.

Processor Speed:

Processor speed stands for the speed at which the CPU execute the instruction . It is measured in megahertz(MHz).

Processor speed depends upon data bus being used by the processor . Data bus is used to transfer data on the processor . These data buses comes in 8 bits (1 byte) data at a time .

System Clock:

Let us see what a system clock plays in a computer . The events inside a computer takes a place at a decide speed which is controlled by an electronic dumber . It is called system clock . This part is an electronic circuit which create pulses at a fast speed which is measured in million of cycle per second . The rate of the processor clock is called its clock speed , and one pulse is called clock ticks . the system clock normally does nothing to maintain time and date . To do all these thing there is a separate circuit in all the computers . The system clock synchronizes the internal activities of a computer.

Thanks for Reading.

SHIVANSHU TIWARI

What is an Operating System.

Introduction:-

An Operating System (OS) is a software that acts as an interface between computer hardware components and the user. Every computer system must have at least one operating system to run other programs. Applications like Browsers, MS Office, Notepad Games, etc., need some environment to run and perform its tasks.

Operating System is a system software . There are a number of Operating system . Single , Multi- Programming , Multi-tasking are few terms very much familiar with the operating system and how to work on same prominent operating system.

Operating system is the first Software that loads after the computer starts . it means it is a mandatory software for booting your computer system . it is not only mandatory for booting computer system but is also essential for running other application software & utility software .

Operating system plays an important role in computer. As one know computer is an electronic device . it can perform the task according to computer given instruction . computer system can be divide in to four components

1. Hardware

2. Operating System

3. Application program

4. User's

In this 4 components OS is a software program.

Why an Operating System:-

Operating system is Mysterious Power which control all hardware and software on computer . It work as a mediator between hardware and software . just because of the OS. The programmer don't need to know the complexity of hardware program communicate with hardware through OS.

Your computer has mainly resource such as memory , Hard disk , CPU , keyboard , Network ,co-ordination etc. The most important objectives of Operating system is to organism them resource . An OS ensure that all the application get proper hardware resources as required and the application get enough CPU times to get their commands processed and they enough memory to store data.

An OS is provide user interface which helps the user to give commands to the OS to run the application of their choice . Today OS provide us graphical interface ,where , instead of typing the commands they are clicked and double click to get them implemented.

Today are many operating system in market but all have same fundamentals but their functional method are different.they functional method are depends upon how they are designed.

Function Of Operating System:-

Process Management:-

Every program running on a computer , be it background services or application , is a process as long as the von Neumann architecture used build computer. only one process per CPU could be run at a time . Older microcomputer OS such as MS_DOS , did not attempt to bypass this limit , with the exception of interrupt processing , only one process could be run under them.

.Process management is an operating system's way of dealing with running multiple processes.since most computer contain one processor with one (or more) core.multitasking is done by simply switching process quickly, depending on operating system. In many system there is a background process , such as the system idle process in window, which will run when no other process is waiting for the CPU.

Memory Management:-

Current computer architecture arrange the computer's memory in a hierarchical manner.starting from fastest register , CPU cache, ran and disk storage memory management is the act of managing computer memory. The management of main memory is critical to the computer system.

The basic objective of memory management system it is provide fast-uninterrupted access by the processor to the memory such that the processor can operate at the speed it is expected to work.

An Operating system memory manager coordinate the use of these various types of memory by tracking which one is available , which is to be allocate or deallocate and how to move data between and how to move data between them . this activity , usually referred to as virtual memory management.increasing the amount of memory available for each process by making the disk storage seem like main memory.There is a speed penalty associate with using disks or other slower storage as memory, if running process required significantly more RAM than is available , the system may start trashing . This can happen either because one process requires a large amount of a memory than is available/ This leads transfer of each process of data to slower storage.

Another important part of memory management is managing virtual address.

Main memory is divide into two parts:-

1.Resident Moniter:

The area of main memory which can be accessed by user process and in this only operating system resides.

2.User Area:

This is the part of main memory where space for the user process allocate.

Disk and File System:-

All operating system include support for a variety of file systems .Modern file system comprise of a hierarchy of dir . While the ideas is conceptually similar across all general purpose file system, some different in implementation exists . Two noticeable example of this are the same char used to seprate dir , & case sensitivity.

Networking:-

A distributed system is a group of processors which do not share memory, hardware devices, or a clock. The processors communicate with one another through the network. .

Security Management:-

Typically an OS offers various services to other network computer and users These services are usually provides through ports or numbered access points beyond the OS network add. Typically services include offering such as file sharing , print service,email,web site, FTP.

At the front line of security are hardware device know as firewalls . at the OS level , there are a number of software firewalls available.

Device Driver:-

A Device Driver is specific type of computer software developed allow interaction with hardware. device Typically this consists an interface for communicating with device , through specific computer bus or communications subsystem that the hardware is connected to, providing commands to and receiving data

from the device.

What is a Kernel?

The kernel is the central component of a computer operating systems. The only job performed by the kernel is to the manage the communication between the software and the hardware. A Kernel is at the nucleus of a computer. It makes the communication between the hardware and software possible. While the Kernel is the innermost part of an operating system, a shell is the outermost one.

Types of Operating System :-

As computer have progressed and developed so have the different types Operating System. The basic of different types is follows:

Batch Operating System

Multi-programmed batch system

personal-computer operating system

Distributed operating system

Simple batch operating system

Time sharing operating system

Real time operating system

Multi processing

Multi tasking operating system etc.

Batch operating system

The users of a batch operating system do not interact with the computer directly. Each user prepares his job on an off-line device like punch cards and submits it to the computer operator. To speed up processing, jobs with similar needs are batched together and run as a group. The programmers leave their programs with the operator and the operator then sorts the programs with similar requirements into batches.

The problems with Batch Systems are as follows −

Lack of interaction between the user and the job.
CPU is often idle, because the speed of the mechanical I/O devices is slower than the CPU.
Difficult to provide the desired priority.

Real Time operating System

A real-time system is defined as a data processing system in which the time interval required to process and respond to inputs is so small that it controls the environment. The time taken by the system to respond to an input and display of required updated information is termed as the response time. So in this method, the response time is very less as compared to online processing.

Real-time systems are used when there are rigid time requirements on the operation of a processor or the flow of data and real-time systems can be used as a control device in a dedicated application. A real-time operating system must have well-defined, fixed time constraints, otherwise the system will fail. For example, Scientific experiments, medical imaging systems, industrial control systems, weapon systems, robots, air traffic control systems, etc.

There are two types of real-time operating systems.

Hard real-time systems

Hard real-time systems guarantee that critical tasks complete on time. In hard real-time systems, secondary storage is limited or missing and the data is stored in ROM. In these systems, virtual memory is almost never found.

Soft real-time systems

Soft real-time systems are less restrictive. A critical real-time task gets priority over other tasks and retains the priority until it completes. Soft real-time systems have limited utility than hard real-time systems. For example, multimedia, virtual reality, Advanced Scientific Projects like undersea exploration and planetary rovers, etc.

Multi-Tasking/Time-sharing Operating systems

Time-sharing operating system enables people located at a different terminal(shell) to use a single computer system at the same time. The processor time (CPU) which is shared among multiple users is termed as time sharing.

Thanks for Reading.

The Linux Booting Process.

In Linux, the login page is handled by the GNOME Display Manager (GDM) or the LightDM. When you press the power button, an electrical signal passes through your system’s motherboard and awakens the entire hardware system. As we all know, the Linux kernel works in a very different method than the traditional booting system. In Linux, the boot process includes a few steps.

Linux’s boot process activates the kernel user mode that activates the BIOS, MBR, boot menu, GRUB, and the login page. To cover the entire method of the Linux booting process, we will also discuss the power supply, hardware setup, hardware virtualization, storage system, RAM, complementary MOS (CMOS) battery, and all the other booting related topics.

The Linux Boot Process consists of several stages. each represent by a different components .the following list is briefly summarizes the boot process and features all the major components involved.

BIOS

BIOS stands for basic input/output system.
The BIOS perform platform (rather than OS ) specific startup task.
The BIOS loaded and executes the partition boot code from the designed boot device,which contain phase 1 of Linux boot loader , phase 1 load phase 2 (the bulk of boot loader code). some ladder may use an intermediate stage to achieve this (know as phase 1.5) since modern large disk may not be fully readable without further code.
once the boot loader program is detected and loaded into the memory , BIOS gives the control to it.
so in a simple term BIOS loads and executes the MBR boot loader.

MBR

MBR stands for Master Boot Record.If you’re thinking about switching from Windows to Linux, there is a chance that you have already heard the term MBR vs. GPT. Master boot record or in the shot MBR is well known among Linux enthusiasts because it is maintainable from the BIOS system. Basically, the MBR partition holds the boot records and the booting related files.
In the Linux system’s boot process, the MBR partition also stores the data about all the other storage drives and how they will be acting on your Linux system. If you mess up with the MBR partition, your Linux system is in trouble.
It only requires 4096 Bits of storage to store the GRUB and Linux booting files inside the MBR partition. Though the MBR partition is found in Linux distributions, the GPT partitioning scheme replaces the MBR table in the modern era. Actually, using the GPT scheme is safer than using the MBR scheme for multiple booting.

so , in simple term MBR loads and executes the GRUB boot loader.

GRUB

GRUB stands for Grand Unified Bootloader.
if you have multiple kernel image installed on your system, you can choose which one to the executed.
GRUB display a splash screen , waits for few second , if you don't enter anything , it loads the default kernel image as specified in the group configuration file.
GRUB has knowledge of file system .
so , in simple word GRUB just load and execute kernel and initrd images .

KERNEL

Kernel () then perform the majority of system setup (interrupts, the rest of memory management device initialization , drivers etc) before spawning separately , the idle process and scheduler , and the init process (which executed in users space).

the scheduler effectively takes control of the system management as the kernel goes dormant (idle).

Kernel executes the /sbin/init program.

initrd stands for initial RAM Disk.

INIT

Looks at the /etc / inittab files to decide the Linux run level.
following are available

0- halt

1- single user mode

2- multi user ,without NFS

3- Full multi user mode

4- Unused

5- x11

6- Reboot

init identifies the default initlevel from / etc / inittab and uses that to load all appropriate programs.
Execute 'grep' init default / etc / inittab on your system to identify the default run level.
the init process execute scripts as need that set up all non-kernel services and structures in order to allow a user environment to be create and than presented the user with a login screen.

RUNLEVEL

When the Linux system is booting up, you might see various services getting started , for example , it might say "start sendmail...OK".Those are the runlevel program , execute from run level dictionary as defined by run level .
Depending on your default init level setting the system will execute the program , execute the program from one on the following directories.

* Run level 0- / etc / rc.d / rc0.d /

* Run level 1- / etc / rc.d / rc1.d /

* Run level 2- / etc / rc.d / rc2.d/ * Run level 3- / etc / rc.d / rc3.d /

* Run level 4- / etc / rc.d / rc4.d/

* Run level 5- / etc / rc.d / rc5.d /

* Run level 6- / etc / rc.d / rc6.d /

pls note that there are also symbolic links available for these directory under / etc directly ,So /etc / rc0.d is linked to / etc / rc.d / rc0.d.
under the /etc / rc.d / rc*.d / directories . you would see program that stared with S and K .
program start during S are used during startup . S for startup.
program start with k are used during shutdown . k for kill.
there are number right s to k in the program names . these are the sequence number which the program should be started or killed.
for example S12 syslog is to start the syslog daemon . which has the sequence number of 12. s80 sendmail is to start the sendmail daemon ,which has sequence number of 80. so, syslog program will be started before send mail.

On shutdown , init is called to close down all user space functionality in a controlled manners , again via scripted direction , following which init terminated and Kernel execute its own shut down.

Virtualization: Enable Virtualization Technology on a Virtual Machine

The hardware virtualization is a setting that you can find inside the BIOS framework. Typically, you do not need to enable the virtualization technology to boot a regular Linux OS on your machine. But, if you are using a mare or a virtual machine to boot the Linux system, you probably need to enable the hardware virtualization feature to accelerate your virtual machine’s efficiency.