What are Virtual Machines..?

A virtual machine uses a combination of software and your existing computer to emulate additional computers, all within one physical device.
Virtual machines provide the ability to emulate a separate operating system (the guest), and therefore a separate computer, from right within your existing OS (the host). This independent instance appears in its own window and is typically isolated as a completely standalone environment, although interactivity between guest and host is often permitted for tasks such as file transfers.

Everyday Reasons For Using a Virtual Machine

There are many reasons why you may want to run a VM, including developing or testing software on various platforms without actually utilizing a second device. Another purpose could be gaining access to applications that are native to an operating system different than your own. An example of this would be wanting to play a game exclusive to Windows when all you have is a Mac.

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In addition, VMs provide a level of flexibility in terms of experimenting that is not always feasible on your main, host operating system. Most VM software allows you to take snapshots of the guest OS, which you can later revert back to if something were to go wrong such as key files becoming corrupted or even a malware infection taking place.

Why Businesses Might Use Virtual Machines

On a grander, non-personal scale, many organizations deploy and maintain several virtual machines.

Rather than having a large number of individual computers running at all times, companies opt to have a bunch of VMs hosted on a much smaller subset of powerful servers, saving money not only on physical space but also on electricity and maintenance. These VMs can be controlled from a single administrative interface and made accessible to employees from their own remote workstations, often spread out across multiple geographical locations.

Because of the isolated nature of the virtual machine instances, companies can even allow users to access their corporate networks via this technology on their own personal computers—adding to both flexibility and cost savings.

Full control is another reason that they are an attractive alternative for admins, as each VM can be manipulated, started and stopped instantly with just a simple mouse click or command line entry. Couple that with real-time monitoring ability and advanced security oversight and virtual machines become quite a viable option.

Common Limitations of Virtual Machines

While VMs are certainly useful, there are notable limitations that need to be understood beforehand so that your performance expectations are realistic. Even if the device hosting the VM contains powerful hardware, the virtual instance itself may run significantly slower than it would on its own independent computer. Advancements in hardware support within VMs have come a long way in recent years, but the fact remains that this limitation will never be completely eliminated.
Another obvious limitation is cost. Aside from the fees associated with some virtual machine software, installing and running an operating system – even within a VM – still requires a license or other authentication method in some instances, depending on the particular OS.

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For example, running a guest instance of Windows 10 requires a valid license key just as it would if you were installing the operating system on an actual PC. While a virtual solution is typically cheaper in most cases than having to purchase additional physical machines, the costs can add up when you require a larger-scale rollout.

Other potential limitations to consider would be lack of support for certain hardware components as well as possible network constraints. With all of that said, as long as you do your research and have realistic expectations going in, implementing virtual machines in your home or business environment could be a real game changer.

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Details about Java Virtual Machine you mus know.

                            
JVM is an specification that provides run-time environment in which java byte-code can be executed.
JVMs are available for many hardware and software platforms (i.e. JVM is platform dependent).

What is JVM

It is:

1. A specification where working of Java Virtual Machine is specified. But implementation provider is independent to choose the algorithm. Its implementation has been provided by Sun and other companies.
2. An implementation Its implementation is known as JRE (Java Runtime Environment).
3. Runtime Instance Whenever you write java command on the command prompt to run the java class, an instance of JVM is created.

What it does

The JVM performs following operation:

• Loads code
• Verifies code
• Executes code
• Provides runtime environment

JVM provides definitions for the:

• Memory area
• Class file format
• Register set
• Garbage-collected heap
• Fatal error reporting etc.

Internal Architecture of JVM

Let’s understand the internal architecture of JVM. It contains classloader, memory area, execution engine etc.

                                

1) Classloader

Classloader is a subsystem of JVM that is used to load class files.

2) Class(Method) Area

Class(Method) Area stores per-class structures such as the runtime constant pool, field and method data, the code for methods.

3) Heap

It is the runtime data area in which objects are allocated.

4) Stack

Java Stack stores frames.It holds local variables and partial results, and plays a part in method invocation and return.

Each thread has a private JVM stack, created at the same time as thread.

A new frame is created each time a method is invoked. A frame is destroyed when its method invocation completes.

5) Program Counter Register

PC (program counter) register. It contains the address of the Java virtual machine instruction currently being executed.

6) Native Method Stack

It contains all the native methods used in the application.

7) Execution Engine

It contains:

1) A virtual processor

2) Interpreter: Read bytecode stream then execute the instructions.

3) Just-In-Time(JIT) compiler: It is used to improve the performance.JIT compiles parts of the byte code that have similar functionality at the same time, and hence reduces the amount of time needed for compilation.Here the term ?compiler? refers to a translator from the instruction set of a Java virtual machine (JVM) to the instruction set of a specific CPU.

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Virus VS Malware

Difference Between Viruses and Malware

These days many of us talk about like malware and spyware a lot more than the virus. Have you ever wondered what exactly are all these?
Beginning with to understand what a virus is we will start with the original biological meaning of the word.                                                                                                        

Biological viruses like the ones that can make you sick are parasitic. They inject their code in this case either DNA or RNA into a host cell as a means of replication this code causes the cell to make a ton of copies of the virus and ultimately burst to send new viruses everywhere. Computer Viruses operate via a similar principle unlike some forms of malware which are fully executable programs.

  Viruses tend to be smaller pieces of code that confused with other programs or  files 
and only replicate when conditions are right. So they can be triggered by a particular date and time opening a certain program or even hitting a certain amount of disk usage. After a virus is triggered, it will try to copy itself and spread infecting other files and programs along the way sometimes over a network and just like real viruses these virus copies can be a little different from the original making it hard for antivirus software to eliminate them. Some even come encrypted making detection even more complicated.

A computer virus can contain a payload that will cause some effect which could be anything from just displaying a joke to permanently corrupting your important data.
To make it simple now, Malware is any computer infection, which includes viruses and malicious software. Since other types of malware can cause these annoying effects, many people have used the terms virus and malware interchangeably, but this is incorrect. Much modern malware like ransomware and adware are also standalone programs that can be passed around and executed on their own.

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How does an Image Sensor Chips and Camera Works.

All webcams work in broadly the same way: they use an image sensor chip to catch moving images and convert them into streams of digits that are uploaded over the Internet. The image sensor chip is the heart of a webcam—so how does that bit work? Let's take a webcam apart and find out.
Take the outer case off a webcam and you'll find it's little more than a plastic lens mounted directly onto a tiny electronic circuit board underneath. The lens screws in and out to increase its focal length, controlling the focus of your cam:

                                            

Now take the lens off and you can see the image sensor (CCD or CMOS chip): it's the square thing in the middle of this circuit. Only the tiny, green-colored central part is light-sensitive: the rest of the chip is concerned with connecting the light detector to the bigger circuit that surrounds it
:

                                            

Here's a closeup:

                                           

Webcams versus digital cameras

So the image sensor is the "electronic eye" of a webcam or a digital camera. It's a semiconductor chip  made of millions of tiny, light-sensitive squares arranged in a grid pattern. These squares are called pixels. Basic webcams use relatively small sensors with just a few hundred thousand pixels (typically a grid of 640 × 480. Good digital cameras use sensors with many more pixels; that's why cameras are compared by how many megapixels (millions of pixels) they have. A basic webcam has about 0.3 megapixels (300,000, in other words), while a digital camera with 6 megapixels has over 20 times more—probably arranged in a rectangle with three thousand across and two thousand down (3000 x 2000 = 6 million). A better camera rated at 12 megapixels would have a 4000 x 3000 pixel sensor. Take a photo the same size with those two cameras and the 12 megapixel one is going to give you 1000 more dots horizontally and 1000 more vertically—smaller dots giving more detail and higher resolution. A single pixel in a really good sensor is something like 10 micrometers (10μm) in diameter (5–10 times smaller than the diameter of a typical human hair)!

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How does an image sensor convert a picture into digital form?

 

                                                      

When you take a digital photo or stare into your webcam, light zooms into the lens. This incoming "picture" hits the image sensor, which breaks it up into individual pixels that are converted into numeric form. CCDs and CMOS chips, the two kinds of image sensor, do this job in slightly different ways. Both initially convert incoming light rays into electricity, much like photoelectric cells (used in things like "magic eye" intruder alarms or restroom washbasins that switch on automatically when you put your hands under the faucet). But a CCD is essentially an analog optical chip that converts light into varying electrical signals, which are then passed on to one or more other chips where they're digitized (turned into numbers). By contrast, a CMOS chip does everything in one place: it captures light rays and turns them into digital signals all on the one chip. So it's essentially a digital device where a CCD is an analog one. CMOS chips work faster and are cheaper to make in high volume than CCDs, so they're now used in most low-cost cellphone cameras and webcams. But CCDs are still widely used in some applications, such as low-light astronomy.
Whether images are being generated by a CMOS sensor or a CCD and other circuitry, the basic process is the same: an incoming image is converted into an outgoing pattern of digital pixels. Let's just refer to "the image sensor" from now on (and forget about whether it's a CCD and other chips or a CMOS sensor). First, the image sensor measures how much light is arriving at each pixel. This information is turned into a number that can be stored on a memory chip inside the camera. Thus, taking a digital photograph converts the picture you see into a very long string of numbers. Each number describes one pixel in the image—how bright or dark and what color it is.

Step by step

• Light from the object (in this case, a bicycle) enters the camera lens.

• The image sensor inside the camera splits the image up into millions of pixels (squares). An LCD display on the back of the camera shows you the image that the sensor is capturing—not an image of the object seen through a series of lenses (as with a conventional camera), but a redrawn, computerized version of the original object displayed on a screen.

• The sensor measures the color and brightness of each pixel.

• The color and brightness are stored as binary numbers (patterns of zeros and ones) in the camera's memory card. When you connect your camera to a computer, these numbers are transmitted instantly down the wire.                  

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Everything You must know About the BITCOINS.

A few days ago, the world has seen the biggest Ransomware attack called WannaCry. The hackers encrypted all the information of victims and asked for Bitcoins to decrypt the data. You may wonder why hackers asked for Bitcoins instead of dollars or euro? What is Bitcoin and Bitcoin mining? What is the reason for asking Bitcoins?
In this article, I am going to share everything you need to know about Bitcoins and how do they work.

What is a Bitcoin?

Bitcoin is the virtual banking currency of the internet also known as ‘cryptocurrency’. It is the world’s “first decentralized digital currency”. A mysterious person known as Satoshi Nakamoto launched bitcoin in 2009. His true identity is still unknown. It has existed for several years now and many people have questions about them such as Where do they come from? Are they legal? Where can you get them?.
Bitcoins are digital coins, you can send over the internet. Compared to other choices, bitcoin have many advantages. They are transferred straight from person to another via Internet without going to the bank. It means that the transactions fees are extremely lower, anyone can use them in every country, the account cannot be frozen and there are no limits.


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Bitcoins are a form of digital public money that is created by painstaking mathematical computations and policed by millions of computer users called ‘miners’. Bitcoins are, in essence, electricity converted into long strings of code that have money value. The value of a single Bitcoin has fluctuated wildly, reaching a high of around $1,000 in late 2013 before falling to less than half that level, and then rebounding in 2016. In 2017, it’s value has reached to $2500 (per bitcoin).

How Does Bitcoin Work? (Bitcoin Mining)

Many currency exchanges exist on the Internet where you can buy and sell bitcoins. Your coins are saved in your digital wallet on your computer or mobile device or any online wallet. Sending and receiving Bitcoins is as easy as sending and receiving email, you can buy anything with Bitcoin.



                           

Bitcoin is underpinned by a peer-to-peer computer network made up of its users’ machines, akin to the networks that underpin BitTorrent, a file-sharing system, and Skype, an audio, video and chat service. Bitcoins are mathematically generated as the computers in this network execute difficult number-crunching tasks, a procedure known as ” Bitcoin mining “.
To use Bitcoin, you need to install Bitcoin wallet. Once you have installed a Bitcoin wallet on your computer or mobile phone, it will generate your first Bitcoin address and you can create more whenever you need one. You can disclose your addresses to your friends so that they can pay you or vice versa. This is pretty similar to how email works but you can use one bitcoin address at once.
The bitcoins system is secured by individuals called Bitcoin miners. Workers or miners are paid newly created bitcoins for verifying transactions. All transactions after verified are recorded in a transparent public record. The mathematics of the Bitcoin system were set up so that it becomes progressively more difficult to “mine” Bitcoins over time, and the total number that can ever be mined is limited to around 21 million. There is therefore no way for a central bank to issue a flood of new Bitcoins and devalue those already in circulation.

 

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Amazing Use of OTG Cable that you might don't Know.

                                                   

USB OTG or the OTG cable is also known as USB On-The-Go cable is the cable which allows USB devices to act as a host which further allows USB devices to be attached with them. The OTG cable is generally used extend the device’s functionality, which allows you to transfer the data from the smartphone to Pen Drive and vice versa. But, there are other interesting uses of the OTG cable which we will figure out in the article below.

Connect a portable hard drive

You can connect the external hard drive to your smartphone with the help of OTG cable. Once the external hard drive is connected, you can easily access all the files on your smartphone. Also, you can transfer the files from phone to the external storage and vice versa with the help of OTG cable.

Connect USB light

You can connect the USB based LED light with your Android phone to light up the LED. Through OTG cable, you can even connect the LED flashlight to capture images at night if your phone doesn’t have front flash feature.

 
                                    
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Share messages and contacts between two phones

You can transfer the contacts, messages and call logs between two Android phones through SmartSwitch App from Samsung and OTG cable. This method of transferring is easy and useful. Also, it consumes less battery.

Connect your camera

If you want to connect your camera with the Android smartphone, then you can connect it using the OTG cable. Also, you don’t have to connect a camera with the computer if you want to clear few pictures through your Android device.

Connect USB fan

USB fans work with the electric charge, but you might have seen Laptop cooling pads which are connected to the device with the help of USB cable. So similarly, you can connect the USB fan with the Android device through an OTG cable.

Connect Ethernet

You can connect wired Internet or the Ethernet on your Android devices using the OTG cable. If you don’t have access to the Wi-Fi or the mobile data then connecting your Android phone with the Ethernet is useful through an OTG cable.

Connect a card reader

If your Android phone doesn’t support MicroSD card, then you can connect the card reader with your phone through an OTG cable. You should have OTG Plus Card reader, which will allow you to connect the MicroSD card with any Android device.

Charge Android phone with another Android phone

You can charge your Android phone with the help of another Android phone through an OTG cable where the USB host will help you to charge the phone. This is the helpful technique if you want to charge your phone in the emergency.

Connect a game controller

You can connect the game controller with your Android device through OTG cable. Many Android games support external gamepad, and you can connect an external game controller through the OTG cable.

Connect LAN cable

You can connect the broadband internet with the Android phone with the help of LAN to USB controller and OTG cable.

Connect Mouse and Keyboard

You can connect the keyboard and mouse with your phone with the help of OTG cable, which is very useful to exchange the messages through keyboard and mouse.

Print saved documents

You can connect the Printer and Android phone with the help of OTG cable to print the documents. You have to install the app called PrintShare which will download the USB drivers on your Android phone.

Create Music

You can connect the musical instruments with PC through MIDI standard cable. But, you can connect the modern musical instruments with your Android phone through OTG cable and create music of your choice.

Record Audio

You can connect the external microphone with your android phone via an OTG cable to record audio on your Android phone. This feature is useful for the YouTubers.

Chromecast

You can use Chromecast or HDMI cable and OTG cable to connect your phone to TV or LED in the USB port. You can mirror your Android screen with the TV and can watch any movies or play audios.


                                    
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How does PING works.

                                  

How does internet ping work

Ping is a type of network packet that is used to check if a machine that you want to connect to over the internet is available or not. A ping is a network packet termed an Internet Control Message Protocol (ICMP) packet. The process of a ping is done when a machine sends an ICMP echo request packet to another machine or interface over the internet. If the receiving machine is available and is enabled to reply back, it will respond with an echo reply packet.

This not only shows us that the receiving machine is alive and working, it also helps us to identify a number of things such as total time taken, loss of packets, etc that are used to judge the reliability of the connection.  To run a ping from your Linux machine, you will need to open a terminal and write a command. The syntax of the command is “ping destination_ip” – replace “destination_ip” with the actual IP address of the machine you want to connect with.

All recent versions of Windows and Linux come enabled with the ICMP command. On Windows, the command will send 4 echo requests before stopping while Linux will continue sending echo requests until a user stops it themselves.

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