WHAT IS BITCOIN?

Bitcoin is the first decentralized peer-to-peer payment network that is powered by its users with no central authority or middlemen. From a user perspective, Bitcoin is perhaps best described as ‘cash for the Internet’, but Bitcoin can also be seen as the most prominent triple entry bookkeeping system in existence.
It is also known as digital cash, cryptocurrency, an international payment network, the internet of money – but whatever you call it, Bitcoin is a revolution that is changing the way everyone sees and uses money.
WHO CREATED BITCOIN?
The original Bitcoin code was designed by Satoshi Nakamoto under MIT open source credentials. In 2008 Nakamoto outlined the idea behind Bitcoin in his White Paper, which scientifically described how the cryptocurrency would function.
Bitcoin is the first successful digital currency designed with trust in cryptography over central authorities. Satoshi left the Bitcoin code in the hands of developers and the community in 2010. Thus far hundreds of developers have added to the core code throughout the years.
WHAT IS THE BLOCKCHAIN?
The blockchain is simply a vast, distributed public ledger of account. It keeps track of every transaction ever made in the network, and all transactions are timestamped and verified by network miners.
This is how it works: miners with specialized computers compete to solve mathematical puzzles with other computers, and once they solve a puzzle they are awarded some Bitcoin, but they also add a “block” of completed transactions to the blockchain for future viewing and verifiability.
Once a block is added to the chain the cycle repeats itself, and the computers continue to compete to solve these difficult problems. Every transaction on the blockchain is completely transparent and accounted for in its log. Anyone can see the public keys of any transaction they want (although there are no names associated with transactions).
One could go all the way back and view the very first transactions ever made on the first block ever created. This block was unironically called the Genesis Block. 
WHAT IS BITCOIN MINING?

One of the most common analogies that people use for Bitcoin is that it’s like mining gold. Just like the precious metal, there is only a limited amount (there will only ever be 21 million Bitcoins) and the more that you take out, the more difficult and resource intensive it is to find.
Apart from that, Bitcoin actually works quite differently and it’s actually quite genius once you can get your head around it.
Bitcoin mining serves to both add transactions to the blockchain and to release new Bitcoin. The mining process involves compiling recent transactions into blocks and trying to solve a computationally difficult puzzle. The first participant who solves the puzzle gets to place the next block on the blockchain and claim the rewards.
The first participant who solves the puzzle gets to place the next block on the blockchain and claim the rewards. The rewards incentivize mining and include both the transaction fees (paid to the miner in the form of Bitcoin) as well as the newly released Bitcoin.
IS IT PROFITABLE TO MINE BITCOIN?
There are many calculators on the web that shows you exactly what the ROI is on any given hash rate when you take into account cost of electricity. Based on how much you spend on your computer hardware or cloud contract and what your electricity cost is, the payback for profitability might be 9-12 months out. So why do miners continue to mine?
Because the calculators only take into account what Bitcoins are worth today. At the time of writing, each Bitcoin is worth $4,000. But if Bitcoin’s value rises to $10,000 by next year, then the ROI on your mining significantly dropped to maybe a few months. And if Bitcoin’s value rises to $100,000 in 3 years, then your ROI would drop to mins. And whatever Bitcoins you’ve mined would be worth 25x more.
Remember Bitcoin has a finite number and as we approach the 21st million Bitcoin, the value will significantly rise.
 IS IT TOO LATE TO INVEST IN BITCOIN?
Anyone who’ve heard about Bitcoin probably has heard stories about early adopters becoming millionaires. Bitcoin’s value has gone from a few cents to $4,000 dollars within a few years and insane amounts of wealth have been generated for those lucky enough who got in early. But those who are reading this are probably wondering if it’s still possible to get rich from Bitcoin today.
 Currently 1 bitcoin will costs you around $7700.{Rs-5,00,000} Its better to start earning bitcoins from today as because its rate is increasing day by day.1 btc = 100,000,000 satoshis.
 At start 1Bitcoin= 9 INR (Rs) only
 last September 1Bitocoin = 70,000 INR (1088$)
 this October 1Bitocoin = 3,70,000 INR (5266$)and Today 11/16/17) 
1 Bitcoin = 486074.14 INR (7464$)(Experts predicted that it will reach 10,000$ in next 1 to 2 years.) Note:Google it 1 BTC to INR or USD it will change 24/7.
Is it too late to invest in bitcoin?
Take a look at Is It Too Late To Invest In Bitcoin to find out here..https://cryptosrus.com/is-it-too-late-to-invest-in-bitcoin/
WHY ARE THERE WILD FLUCTUATIONS WITH BITCOIN PRICES?
Since people now have access to Bitcoin anywhere in the world, whenever there is any news about inflation, currency devaluations, war, trade issues, etc… people usually bulk up on Bitcoin from that country or region. And whenever there is news about Bitcoin exchanges being hacked or halting withdraws, influential people calling Bitcoin fraud or bubble, Bitcoin dips based on fear.

Since the total market cap in Bitcoin is still relatively small (Around $70 billion), these buying sprees and selling sprees can result in these wild fluctuations. But as the market cap increases, these fluctuations become smaller and smaller.
Wireless LAN Basics  IEE802.11

IEEE802.11 Overview
                       The fundamental building block of the 802.11 architec is the cell, known as the basic service set (BSS) in 802.11 parlance. A BSS typically contains one or more wireless stations and a central base station, known as an access point (AP) in 802.11terminology.
            This is on IEEE 802.11 WiFi training is designed for people who work on development, testing and verification of IEEE 802.11 protocol. Students/Developer  will learn the internals of IEEE 802.11 protocol that helps them with a much better understanding of their current IEEE 802.11 work.
       
 OSI LAYERS:
The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to their underlying internal structure and technology.
Upper layers:
  • 7. application
  • 6. presentation
  • 5. session
Lower layers:
  • 4. transport
  • 3. network
  • 2. data link
  • 1. physical
What is the difference between WLAN and WiMAX?
                        Answer-1.WLAN is used as wireless local area network for providing connectivity between WLAN compliant devices. WiMAX is used as wide area network for providing access between various wireless devices. WLAN standards are evolving including 11a, 11b, 11g, 11n, 11ac, 11ad and more. WiMAX follows IEEE standards viz. 16d and 16e
WLAN Network Basics
WLAN network topology
– Infrastructure Mode
– Repeater Mode
– Bridge Mode
– Ad-hoc Mode
Channel scanning and synchronization
– Passive Scan
– Active Scan
Authentication and association
– Open Authentication
– Shared Key Authentication
Explain the WLAN physical layer frame as per 802.11a?
         WLAN has physical layer frame formats different in 11a, 11b, 11g, 11n and 11ac? They all have three generic fields i.e. preamble, header and data payload (PSDU). Preamble carries STF (short training field) and LTF (long training field) used for front end synchronization. Front end synchronization includes time offset estimation and correction; frequency offset estimation and correction and channel estimation and equalization. Header carries two important parameters rate and length. Rate specify modulation-code rate of the data payload part and length field specify length of data payload in units of OFDM symbol
         What is the difference between 802.11a, 11b, 11g and 802.11n? Answer-3.The difference between the 11a, 11b, 11g and 11n lies in terms of data rate, frequency of operation, distance coverage and more

Physical Layer Technologies
Radio channels and frequencies
– Frequency Channel Allocation for 802.11a/b/g
Modulation technologies
– Direct Sequence Spread Spectrum
– Orthogonal Frequency Division Multiplexing (OFDM)
PHY data rates used
– 802.11b
– 802 11a
– 802 11g
– 802 11n
Improving data transfer:diversity and polarization
– Antenna Diversity
– Polarization
What are the messages exchange between STA and AP in WLAN?
         There are various messages exchanged between Station (STA) and Access Point (AP) in a WLAN network for various purpose such as establishing connection, data transfer, terminate the connection and more. Access points are devices which help extend wired network with wireless capabilities
What is the change in WLAN-11ac with respect to previous versions of WLAN
               WLAN-11ac has been introduced after previous version of WLAN which include 802.11a, 11b, 11g and 11n. 80MHz channel bandwidth is added
Wireless LAN Standards
802.11a – 54 Mbps standard, 5 GHz signaling (ratified 1999)
802.11b – 11 Mbps standard, 2.4 GHz signaling (1999) 11 Mbps standard, 2.4 GHz signaling (1999)
802.11c – operation of bridge connections (moved to 802.1)
802.11d – worldwide compliance with regulations for use of wireless signal
spectrum (2001)
802 11e – Quality of Service (QoS) support (2005)
802.11f – Inter access point protocol to support roaming clients (2003)
802.11g – 54 Mbps standard, 2.4 GHz signaling (2003)
802.11h – Enhanced version of 802.11a to support European regulatory
requirements (2003)
802.11i – Security improvements for the 802.11 family (2004)
802.11j – Enhancements to 5 GHz signaling to support Japan regulatory
requirements (2004) requirements (2004)
802.11k – WLAN system management (in progress)
802.11l – Skipped to avoid confusion with 802.11i

What is the difference between WiFi and Bluetooth?
         WiFi fall under WLAN category while Bluetooth fall under WPAN category. WLAN specifications are published under IEEE 802.11 and Bluetooth under IEEE 802.15 standards. Bluetooth is the standard for wireless personal area networks or WPAN. It allows high speed transmission of data over very short distances.
802.11m – Maintenance of 802.11 family documentation
802.11n – Future 100+ Mbps standard (in progress)
Protocol Architecture
The Physical Medium Dependent Layer
The Data Link Layer
The Network Layer
The Transport Layer
Explain OSI stack and differentiate with TCPIP protocol stack?
        OSI protocol stack is the generic stack developed to make it easy for different manufacturers devices inter-operate without any interfacing issues. TCP IP stack is specifically designed for internet applications. 
802.11 MAC Protocol
Framing data to be transmitted
– Management Frames
– Control Frames
– Data Frames
Spacing between frames
– Inter Frame Spaces (IFS)
Avoiding collisions: carrier sensing
– Physical Carrier Sensing
– Virtual Carrier Sensing
What is the difference between ad-hoc and infrastructure mode in IEEE 802.11? \
          In ad-hoc mode WLAN mobile and stationary terminals referred as STAs (stations) communicate directly. In the infrastructure mode STAs communicate via entity called as AP (Access Point). It is similar to mesh and star topologies used in other wireless networks. Infrastructure mode used to connect with wired network.
Security Protocols in WLANs
Common WLAN Attacks
– Passive Attacks: eavesdropping
– PHY Layer attacks: RF Jamming
– Active Attacks: hacking
– Man in the Middle Attack
WLAN Security Solutions
– WEP-SharedKey
– WPA-PSK
– WPA-Open
– Server Based Authentication
– Server-based security: 802.1x / 802.11i
Newton’s laws of motion

Newton’s laws of motion:
Relations between the forces acting on a body and the motion of the body, first formulated by English physicist and mathematician Sir Isaac Newton.


Newton’s first law:

 It states that, if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force. This postulate is known as the law of inertia. The law of inertia was first formulated by Galileo Galilei for horizontal motion on Earth and was later generalized by René Descartes. 
Before Galileo it had been thought that all horizontal motion required a direct cause, but Galileo deduced from his experiments that a body in motion would remain in motion unless a force (such as friction) caused it to come to rest. 

Newton’s second law:

It is a quantitative description of the changes that a force can produce on the motion of a body. It states that the time rate of change of the momentum of a body is equal in both magnitude and direction to the force imposed on it. The momentum of a body is equal to the product of its mass and its velocity. Momentum, like velocity, is a vector quantity, having both magnitude and direction. 
A force applied to a body can change the magnitude of the momentum, or its direction, or both. Newton’s second law is one of the most important in all of physics.
 For a body whose mass m is constant, it can be written in the form F = ma, where F (force) and a (acceleration) are both vector quantities. If a body has a net force acting on it, it is accelerated in accordance with the equation. Conversely, if a body is not accelerated, there is no net force acting on it.
          A lesson proving immovable objects and unstoppable forces are one and the same.


Newton’s third law states:
That when two bodies interact, they apply forces to one another that are equal in magnitude and opposite in direction. The third law is also known as the law of action and reaction. This law is important in analyzing problems of static equilibrium, where all forces are balanced, but it also applies to bodies in uniform or accelerated motion. The forces it describes are real ones, not mere bookkeeping devices. 
For example, a book resting on a table applies a downward force equal to its weight on the table. According to the third law, the table applies an equal and opposite force to the book. This force occurs because the weight of the book causes the table to deform slightly so that it pushes back on the book like a coiled spring. 

            In the 20th century Newton’s laws were replaced by quantum mechanics and relativity as the most fundamental laws of physics. Nevertheless, Newton’s laws continue to give an accurate account of nature, except for very small bodies such as electrons or for bodies moving close to the speed of light. Quantum mechanics and relativity reduce to Newton’s laws for larger bodies or for bodies moving more slowly.

mechanics:
   Newton’s laws of motion and equilibrium
                    science concerned with the motion of bodies under the action of forces, including the special case in which a body remains at rest. Of first concern in the problem of motion are the forces that bodies exert on one another. This leads to the study of such topics as gravitation, electricity.
evolution: 
 Genetic equilibrium: the Hardy-Weinberg law
     They were, evolution could not occur. Why, then, is the law significant if its assumptions do not hold true in nature? The answer is that it plays in evolutionary studies a role similar to that of Newton’s first law of motion in mechanics. Newton’s first law says that a body not acted upon by a net external force remains at rest or maintains a constant velocity.
Physics
Mechanics: Dimensions and Units

                    There is a difference between dimensions and units. A dimension is a measure of a physical variable (without numerical values), while a unit is a way to assign a number or measurement to that dimension.


 For example, length is a dimension, but it is measured in units of feet (ft) or meters (m).

               There is one most common primary unit systems, The International System of Units (SI units, from Le System International d’Unites, more commonly simply called metric units)

                 In total, there are seven primary dimensions. Primary (sometimes called basic) dimensions are defined as independent or fundamental dimensions, from which other dimensions can be obtained.

                 The primary dimensions are: mass, length, time, temperature, electric current, amount of light, and amount of matter. For most mechanical and thermal science analyses, however, only the first four of these are required. The others will not be of concern to most mechanical engineering analyses.


            SI derived units include the hertz , the newton , the pascal (unit of pressure or stress) , the ohm , the farad , the joule , the coulomb , the tesla , the lumen , the becquerel , the siemen , the volt , and the watt .
SI base units:
              
  The meter (abbreviation, m) is the SI unit of displacement or length. One meter is the distance traveled by a ray of electromagnetic (EM) energy through a vacuum in 1/299,792,458 (3.33564095 x 10 -9 ) second. 
  The kilogram (abbreviation, kg) is the SI unit of mass. It is defined as the mass of a particular international prototype made of platinum-iridium and kept at the International Bureau of Weights and Measures. It was originally defined as the mass of one liter (10 -3cubic meter) of pure water.
  The second (abbreviation, s or sec) is the SI unit of time. One second is the time that elapses during 9.192631770 x 10 9 cycles of the radiation produced by the transition between two levels of Cesium 133. 
  The kelvin (abbreviation K), also called the degree Kelvin (abbreviation, o K), is the SI unit of temperature. One Kelvin is 1/273.16 (3.6609 x 10 -3 ) 
  The ampere (abbreviation, A) is the SI unit of electric current. One ampere is the current that would produce a force of 0.0000002 (2 x 10 -7 ) newton between two straight, parallel, perfectly conducting wires having infinite length and zero diameter, separated by one meter in a vacuum.
 The candela (abbreviation, cd) is the SI unit of luminous intensity. It is the electromagnetic radiation, in a specified direction, that has an intensity of 1/683 (1.46 x 10 -3 ) watt per steradian.
   
What is F and O in Share Market?

Futures:
                A futures contract is a contract between two parties to buy or sell an asset for a price agreed upon today with delivery and payment occurring at a future point, the delivery date.
                This means you agree to buy or sell the underlying security at a 'future' date. If you buy the contract, you promise to pay the price at a specified time. If you sell it, you must transfer it to the buyer at a specified price in the future.
What is an options contract ?
                  This gives the buyer the right to buy/sell the underlying asset at a predetermined price, within, or at end of a specified period. He is, however, not obligated to do so. The seller of an option is obligated to settle it when the buyer exercises his right.
How can the contract be settled? 
                   The contract will expire on a pre-specified expiry date (for example, it is the last Thursday of the month for equity futures contracts). Upon expiry, the contract must be settled by delivering the underlying asset or cash. You can also roll over the contract to the next month. If you do not wish to hold it till expiry, you can close it mid-way.


Options:
                 An option is a contract which gives the buyer (the owner) the right, but not the obligation, to buy or sell an underlying asset or instrument at a specified strike price on or before a specified date. The seller has the corresponding obligation to fulfill the transaction – that is to sell or buy – if the buyer (owner) "exercises" the option. The buyer pays a premium to the seller for this right.
 Leverage: Options help you profit from changes in share prices without putting down the full                    price of the share. You get control over the shares without buying them outright.

  Hedging : They can also be used to protect yourself from fluctuations in the price of a share and            letting you buy or sell the shares at a pre-determined price for a specified period of time.
 Though they have their advantages
            In this trading in options is more complex than trading in regular shares. It calls for a good understanding of trading and investment practices as well as constant monitoring of market fluctuations to protect against losses.
‘CALL’ Option :
                    The ‘Call Option’ gives the holder of the option the right to buy a particular asset at the strike price on or before the expiration date in return for a premium paid upfront to the seller. Call options usually become more valuable as the value of the underlying asset increases. Call options are abbreviated as ‘C’ in online quotes.
Example:
v  Step1:Purchase 1 Lot of TCS May  3000 Call option, Spot price Rs.2900/Share
v  Step2:Pay premium of 25000 or Rs.250/Share          
v  Step3:If spot Price Exceeds Rs.3250,Exercise option
v  Step4:If spot price under Rs.3250 on Expiry, Let option Expire 
                    This means, under this contract, Karthick has the rights to buy one lot of 100 Infosys shares at Rs 3000 per share any time between now and the month of May. He paid a premium of Rs 250 per share. He thus pays a total amount of Rs 25,000 to enjoy this right to sell.
Now, suppose the share price of TCS rises over Rs 3,000 to Rs 3200, Karthick can consider exercising the option and buying at Rs 3,000 per share. He would be saving Rs 200 per share; this can be considered a tentative profit. However, he still makes a notional net loss of Rs 50 per share once you take the premium amount into consideration. For this reason, Karthick may choose to actually exercise the option once the share price crosses Rs 3,250 levels. Otherwise, he can choose to let the option expire without being exercised.
‘PUT’ Option :
             The Put Option gives the holder the right to sell a particular asset at the strike price anytime on or before the expiration date in return for a premium paid up front. Since you can sell a stock at any given point of time, if the spot price of a stock falls during the contract period, the holder is protected from this fall in price by the strike price that is pre-set. This explains why put options become more valuable when the price of the underlying stock falls.
Similarly, if the price of the stock rises during the contract period, the seller only loses the premium amount and does not suffer a loss of the entire price of the asset.
Month
Price
Premium
February (Current month)
Rs 1040 Spot
NA
May
Rs 1050 Put
Rs 10
May
Rs 1070 Put
Rs 30

Karthick buys 1000 shares of Company X Put at a strike price of 1070 and pays
Rs 30 per share as premium. His total premium paid is Rs 30,000.
If the spot price for Company X falls below the Put option Karthick bought, say to Rs 1020; Karthick can safeguard his money by choosing to sell the put option. He will make Rs 50 per share (Rs 1070 minus Rs 1020) on the trade, making a net profit of Rs 20,000 (Rs 50 x 1000 shares – Rs 30,000 paid as premium).
Alternately, if the spot price for Company X rises higher than the Put option, say Rs 1080; he would be at a loss if he decided to exercise the put option at Rs 1070. So, he will choose, in this case, to not exercise the put option. In the process, he only loses Rs 30,000 – the premium amount; this is much lower than if he had exercised his option.