Interview Questions-Basics of Electronics and Communication Engg

1. Interview Questions-Basics of Electronics and Communication Engg

Sanjeev Bahadur

2.

3. Doping in Semiconductors

• In semiconductor production, doping
deliberately introduces impurities into an
extremely pure ( referred as intrinsic)
semiconductor for the purpose of changing or
modulating its electrical properties.
The impurities are dependent on the type of
semiconductor. Lightly and moderately doped
semiconductors are referred to as extrinsic.
Semiconductor doped to such high levels that it
acts more like a conductor than a semiconductor
is referred to as degenerate.

4. Silicon and Ge as Semiconductor Material

• The semiconductor materials are either basic
such as silicon and germanium or compound
such as gallium arsenide.
Silicon is the most used semiconductor for
discrete devices and integrated circuits. One of
the prominent German scientists wrote in an
article about silicon that this era is the silicon era
since silicon impacted and still affecting the
modern civilization development very much..

5. Diodes

• Diodes are used in circuits to stop electricity
from flowing back into the circuit. They only let
current through in one direction. The diodes in
the distortion pedal are what make the
distortion. Diode-clipping distortion is what this
is called!
There is a certain way to connect diodes. It is
pretty straight forward.
There is always some sort of line on a diode
(except for LED's) but on regular diodes there is
always a line

6. Zener Diodes

7. Zener diode is a diode which allows current to flow in the forward direction

• A Zener diode is a diode which allows current to flow in the
forward direction in the same manner as an ideal diode, but also
permits it to flow in the reverse direction when the voltage is above
a certain value known as the breakdown voltage, "Zener knee
voltage", "Zener voltage", "avalanche point", or "peak inverse
voltage".
• The device was named after Clarence Zener, who discovered this
electrical property. Strictly speaking, a Zener diode is one in which
the reverse breakdown is due to electron quantum tunnelling under
high electric field strength—the Zener effect. However, many diodes
described as "Zener" diodes rely instead on avalanche breakdown as
the mechanism. Both types are used with the Zener effect
predominating under 5.6 V and avalanche breakdown above.

8. NPN Transistor,Schematic

Shown here are schematic symbols and physical diagrams of these two transistor types.

9. Bipolar Transistor

• A bipolar transistor consists of a three-
layer "sandwich" of doped (extrinsic)
semiconductor materials, either P-N-P or
N-P-N.
• Each layer forming the transistor has a
specific name, and each layer is provided
with a wire contact for connection to a
circuit.

10. PNP Transistor

11. NPN Transistor

12. Satellite Dish

13. Logic Circuits and Truth Table-Examples

Logic Circuits and Truth TableExamples

14. Example of Circuit Diagram

• The 555 timer IC is an integrated circuit
(chip) used in a variety of timer, pulse
generation, and oscillator applications.
The 555 can be used to provide time
delays, as an oscillator, and as a flip-flop
element.

15. Amplifiers

16. SMPS Power Supply

17. Switched Mode Power Supplies (SMPS).

• D.C. to D.C. converters and D.C. to A.C. Converters
belong to the category of Switched Mode Power
Supplies (SMPS).
Various types of voltage regulators, used in Linear
Power Supplies (LPS), fall in the category of dissipative
regulator, as they have a voltage control element
usually transistor or zener diode which dissipates power
equal to the voltage difference between an unregulated
input voltage and a fixed supply voltage multiplied by
the current flowing through it.
The switching regulator acts as a continuously variable
power converter and hence its efficiency is barely
affected by the voltage difference .

18. SMPS

• The input D.C. Supply is chopped at a higher frequency
around 15 to 50 kHz using an active device like the BJT,
power MOSFET or SCR and the converter transformer.
Here the size of the ferrite core reduces inversely with
the frequency.
The lower limit is around 5 kHz for silent operation and
an upper limit of 50 kHz to limit the losses in the choke
and in active switching elements.
The transformed wave form is rectified and filtered. A
sample of the output voltage is used as the feedback
signal for the drive circuit for the switching transistor to
achieve regulation.

19. RAM and ROM

20. Block Diagram-Computer

21. Cache Memory

• Small memories on or close to the CPU can operate faster than the
much larger main memory. Most CPUs since the 1980s have used
one or more caches, and modern high-end embedded, desktop and
server microprocessors may have as many as half a dozen, each
specialized for a specific function. Examples of caches with a
specific function are the D-cache and I-cache (data cache and
instruction cache).
• Translation lookaside buffer Main article: Translation lookaside
buffer
A memory management unit (MMU) that fetches page table
entries from main memory has a specialized cache, used for
recording the results of virtual address to physical address
translations. This specialized cache is called a translation
lookaside buffer (TLB]
Disk cache:
• Page cache
• While CPU caches are generally managed entirely by hardware, a
variety of software manages other caches. The page cache in main

22. Disk Buffer

• While the hard drive's hardware disk buffer is sometimes misleadingly
referred to as "disk cache", its main functions are to write sequencing and
read pre fetching. Repeated cache hits are relatively rare, due to the small
size of the buffer in comparison to the drive's capacity. However, high-end
disk controllers often have their own on-board cache of hard disk data
blocks.
Finally, a fast local hard disk can also cache information held on even
slower data storage devices, such as remote servers (web cache) or local
tape drives or optical jukeboxes. Such a scheme is the main concept of
hierarchical storage management.
Web cache
Web browsers and web proxy servers employ web caches to store previous
responses from web servers, such as web pages and images. Web caches
reduce the amount of information that needs to be transmitted across the
network, as information previously stored in the cache can often be reused. This reduces bandwidth and processing requirements of the web
server, and helps to improve responsiveness for users of the web.
Web browsers employ a built-in web cache, but some internet service
providers or organizations also use a caching proxy server, which is a web
cache that is shared among all users of that network.

23. Intel Core 2 Duo Processor& Motherboard

Intel Core 2 Duo Processor&
Motherboard

24. VLSI Chip

VLSI VL82C106 Super I/O chip

25. Plotter

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28. Raster and Vector Graphics

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33. Satellite Dish

• When the signal reaches the viewer's house, it is
captured by the satellite dish. A satellite dish is
just a special kind of antenna designed to focus
on a specific broadcast source.
The standard dish consists of a parabolic
(bowl-shaped) surface and a central feed horn.
To transmit a signal, a controller sends it
through the horn, and the dish focuses the
signal into a relatively narrow beam.

34.

The curved dish focuses incoming radio waves onto the feed horn

35. Radio Spectrum

• Radio spectrum refers to the part of the electromagnetic
spectrum corresponding to radio frequencies – that is, frequencies
lower than around 300 GHz (or, equivalently, wavelengths longer
than about 1 mm). Electromagnetic waves in this frequency range,
called radio waves, are used for radio communication and various
other applications, such as heating.
• The generation of radio waves is strictly regulated by the
government in most countries, coordinated by an international
standards body called the International Telecommunications Union
(ITU). Different parts of the radio spectrum are allocated for
different radio transmission technologies and applications. In some
cases, parts of the radio spectrum is sold or licensed to operators of
private radio transmission services (for example, cellular telephone
operators or broadcast television stations).
• Ranges of allocated frequencies are often referred to by their
provisioned use (for example, cellular spectrum or television
spectrum

36. VHF-Very High Frequencies

• Very high frequency (VHF) is the ITU designation for
the range of radio frequency electromagnetic waves
from 30 MHz to 300 MHz, with corresponding
wavelengths of ten to one meters. Frequencies
immediately below VHF are denoted high frequency
(HF), and the next higher frequencies are known as ultra
high frequency (UHF).
Common uses for VHF are FM radio broadcasting,
television broadcasting, land mobile stations (emergency,
business, private use and military), long range data
communication up to several tens of kilometres with
radio modems, amateur radio, and marine
communications.
Air traffic control communications and air navigation
systems (e.g. VOR, DME & ILS) work at distances of 100
kilometres or more to aircraft at cruising altitude.

37. AM and FM

• AM (or Amplitude Modulation) and FM (or
Frequency Modulation) are ways of broadcasting
radio signals. Both transmit the information in the form
of electromagnetic waves.
AM works by modulating (varying) the amplitude of the
signal or carrier transmitted according to the information
being sent, while the frequency remains constant.
This differs from FM technology in which information
(sound) is encoded by varying the frequency of the wave
and the amplitude is kept constant.

38. Amplitude Modulation

• In AM, a radio wave known as the "carrier" or
"carrier wave" is modulated in amplitude by the
signal that is to be transmitted. The frequency
and phase remain the same.
AM has poorer sound quality compared with FM,
but is cheaper and can be transmitted over long
distances. It has a lower bandwidth so it can
have more stations available in any frequency
range.AM radio ranges from 535 to 1705 KHz
(OR) Up to 1200 bits per second.

39. AM-Tx and Rx

• Transmitter and receiver are simple but
syncronization is needed in case of SSBSC
AM carrier.

40. Frequency Modulation

• In FM, a radio wave known as the "carrier" or
"carrier wave" is modulated in frequency by the
signal that is to be transmitted.
The amplitude and phase remain the same.FM
is less prone to interference than AM. However,
FM signals are impacted by physical barriers.
FM has better sound quality due to higher
bandwidth.FM radio ranges in a higher spectrum
from 88 to 108 MHz. (OR) 1200 to 2400 bits per
second.

41. FM-TX and RX

• Transmitter and receiver are more
complex as variation of modulating signal
has to be converted and detected from
corresponding variation in frequencies.(i.e.
voltage to frequency and frequency to
voltage

42. Signal-to-noise ratio (often abbreviated SNR or S/N

• Signal-to-noise ratio (often abbreviated SNR or S/N)
is a measure used in science and engineering that
compares the level of a desired signal to the level of
background noise. It is defined as the ratio of signal
power to the noise power, often expressed in decibels. A
ratio higher than 1:1 (greater than 0 dB) indicates more
signal than noise. While SNR is commonly quoted for
electrical signals, it can be applied to any form of signal
(such as isotope levels in an ice core or biochemical
signaling between cells).
The signal-to-noise ratio, the bandwidth, and the
channel capacity of a communication channel are
connected by the Shannon–Hartley theorem

43. Satellite telephone, Satellite phone

• A satellite telephone, satellite phone, or
satphone is a type of mobile phone that
connects to orbiting satellites instead of
terrestrial cell sites.
They provide similar functionality to terrestrial
mobile telephones; voice, short messaging
service and low-bandwidth internet access are
supported through most systems.
Depending on the architecture of a particular
system, coverage may include the entire Earth,
or only specific regions.

44. Satphone

• A fixed installation, such as one used aboard a ship, may include
large, rugged, rack-mounted electronics, and a steerable microwave
antenna on the mast that automatically tracks the overhead
satellites.
• Smaller installations using VoIP over a two-way satellite broadband
service such as BGAN or VSAT bring the costs within the reach of
leisure vessel owners. Internet service satellite phones have
notoriously poor reception indoors, though it may be possible to get
a consistent signal near a window or in the top floor of a building if
the roof is sufficiently thin.
• The phones have connectors for external antennas that can be
installed in vehicles and buildings. The systems also allow for the
use of repeaters, much like terrestrial mobile phone systems.

45. Geosynchronous satellite

• A geosynchronous satellite is a satellite in
geosynchronous orbit, with an orbital period the same as
the Earth's rotation period. Such a satellite returns to the
same position in the sky after each sidereal day, and
over the course of a day traces out a path in the sky that
is typically some form of analemma.Orbit si about 36000
kms above a point of Earth.
A special case of geosynchronous satellite is the
geostationary satellite, which has a geostationary
orbit – a circular geosynchronous orbit directly above the
Earth's equator. Another type of geosynchronous orbit
used by satellites is the Tundra elliptical orbit

46. Advantage of Geosynchronous satellites

• Geosynchronous satellites have the advantage of
remaining permanently in the same area of the sky, as
viewed from a particular location on Earth, and so
permanently within view of a given ground station.
Geostationary satellites have the special property of
remaining permanently fixed in exactly the same position
in the sky, meaning that ground-based antennas do not
need to track them but can remain fixed in one direction.
Such satellites are often used for communication
purposes; a geosynchronous network is a
communication network based on communication with or
through geosynchronous satellites.

47. Cybersecurity standards

• Cybersecurity standards are security
standards which enable organizations to practice
safe security techniques to stop cybersecurity
attacks.
These guides provide general outlines as well as
specific techniques for implementing
cybersecurity.
For certain standards, cybersecurity
certification by an accredited body can be
obtained. There are many advantages to
obtaining certification including the ability to get
cybersecurity insurance.

48. Digital signal processing (DSP)

• Digital signal processing (DSP) is the mathematical manipulation
of an information signal to modify or improve it in some way. It is
characterized by the representation of discrete time, discrete
frequency, or other discrete domain signals by a sequence of
numbers or symbols and the processing of these signals.
The goal of DSP is usually to measure, filter and/or compress
continuous real-world analog signals. Usually, the first step is
conversion of the signal from an analog to a digital form, by
sampling and then digitizing it using an analog-to-digital converter
(ADC), which turns the analog signal into a stream of discrete
digital values. Often, however, the required output signal is also
analog, which requires a digital-to-analog converter (DAC). Even if
this process is more complex than analog processing and has a
discrete value range, the application of computational power to
signal processing allows for many advantages over analog
processing in many applications, such as error detection and
correction in transmission as well as data compression
Digital signal processing and analog signal processing are
subfields of signal processing. DSP applications include audio and
speech signal processing, sonar and radar signal processing,
sensor array processing, spectral estimation, statistical signal
processing, digital image processing

49. 2D and 3D visualization

Today’s complex products require a new design approach where multiple boards can
managed as a single design with 2D and 3D visualization.

50. 3D product visualization

• 3D product visualization is becoming a
critical need as the electrical and
mechanical designs converge with little
room for error. Detection at the prototype
phase may be too late.

51. Computer-aided technologies (CAx)

• Computer-aided technologies (CAx is a broad term that means the use
of computer technology to aid in the design, analysis, and manufacture of
products.
Advanced CAx tools merge many different aspects of the product lifecycle
management (PLM), including design, finite element analysis (FEA),
manufacturing, production planning, product
Computer-aided design (CAD)
Computer-aided engineering (CAE)
Computer-aided industrial design (CAID)
Computer-aided manufacturing (CAM)
Computer-aided requirements capture (CAR)
Computer-aided rule definition (CARD)
Computer-aided rule execution (CARE)
Computer-aided software engineering (CASE)
Computer-assisted surgery (CAS)
– Computer-aided surgical simulation (CASS)
• Computational fluid dynamics (CFD)

52. Chip-Package-Board Co-design

Chip-Package-Board Codesign
• Poor I/O assignments on a newly designed
package can leave a PCB unroutable.
Merging the packaging and PCB design
into a single design solution significantly
increases design quality.

53. Flow Architect Studio 3D

54. Flow Architect Studio 3D

• Flow Architect Studio 3D is a software
package for design and presentation. It
enables you to design and visualize in 3D,
any scene you need for example:
buildings, interiors, spaces or your
products.
• Flow helps you to present your work to
others with screenshots, movies and a
real-time virtual 3D walkthrough

55. Digital image processing

• Digital image processing is the use of computer
algorithms to perform image processing on digital
images. As a subcategory or field of digital signal
processing, digital image processing has many
advantages over analog image processing.
It allows a much wider range of algorithms to be
applied to the input data and can avoid problems such
as the build-up of noise and signal distortion during
processing. Since images are defined over two
dimensions (perhaps more) digital image processing may
be modeled in the form of multidimensional systems

56. Photogrammetry

• Photogrammetry is the science of making
measurements from photographs, especially for
recovering the exact positions of surface points.
Moreover, it may be used to recover the motion
pathways of designated reference points located on any
moving object, on its components and in the
immediately adjacent environment.
Photogrammetry may employ high-speed imaging and
remote sensing in order to detect, measure and record
complex 2-D and 3-D motion fields (see also sonar,
radar, lidar etc.). Photogrammetry feeds the
measurements from remote sensing and the results of
imagery analysis into computational models in an
attempt to successively estimate, with increasing
accuracy, the actual, 3-D relative motions within the
researched field.

57. Rugged Computers

Latitude 12 Rugged Extreme
12" fully rugged flip-hinge convertible notebook
that adapts to changing conditions with a crisp
outdoor-readable display and glove-capable
multi-touch.

58. What Is A Klystron? And How Does It Work

Now that we have caught up on basic tube theory, and understand how a beam of
electrons can be formed in a vacuum, we are well on our way to understanding how a
KLYSTRON operates.
If we have a device, which generates a beam of electrons, we notice that the
electrons flow in a smooth steady stream at a particular uniform velocity. The area of
the tube that the electron beam travels down is known as the DRIFT TUBE. If we
insert, within the beam a grid, we can use this grid to control the beam. As we
increase the positive potential on the grid, (assuming that we do not go over a
certain potential which is less than the anode voltage), the electrons will be attracted
to the grid, and by means of attraction, will be accellerated. On the other hand,
should we decrease the potential, making it more negative, it will have the opposite
effect on the beam, and try to slow down the electrons.
We insert two grids, properly spaced for our experiment, and apply an alternating
current source to the grids, such that as one grid swings positive, the other swings
negative. This would mean that the electrons which are aproaching the positive going
grid will be speeding up, as the ones aproaching the negative going grid will be
slowing down. As the phase of the AC cycle changes 180 degrees, we have the same
effect, only backwards. The result would be a sort of "slinky" effect, where the
electron beam is interrupted, and moves along in bursts. This effect is known as
VELOCITY MODULATION. In German, they say that electrons are moving in
"Klystern". (Klyster is the German word for CLUSTER or BUNCH). Hence, the name
Klystron.
On the other end of our experimental Klystron, we have two more grids installed. The
purpose of these are to "feel" the now pulsing beam of electrons as it passes by them

59. Maxwell's equations

• Maxwell's equations are a set of partial differential equations that, together with
the Lorentz force law, form the foundation of classical electrodynamics, classical
optics, and electric circuits. These fields in turn underlie modern electrical and
communications technologies. Maxwell's equations describe how electric and
magnetic fields are generated and altered by each other and by charges and
currents. They are named after the Scottish physicist/mathematician James Clerk
Maxwell, who published an early form of those equations between 1861 and 1862.
The equations have two major variants. The "microscopic" set of Maxwell's
equations uses total charge and total current, including the complicated
charges and currents in materials at the atomic scale; it has universal
applicability but may be unfeasible to calculate. The "macroscopic" set of
Maxwell's equations defines two new auxiliary fields that describe largescale behavior without having to consider these atomic scale details, but it
requires the use of parameters characterizing the electromagnetic
properties of the relevant materials.
The term "Maxwell's equations" is often used for other forms of Maxwell's equations.
For example, space-time formulations are commonly used in high energy and
gravitational physics. These formulations, defined on space-time rather than space
and time separately, are manifestly compatible with special and general relativity. In
quantum mechanics and analytical mechanics, versions of Maxwell's equations based
on the electric and magnetic potentials are preferred.
Since the mid-20th century, it has been understood that Maxwell's equations are not
exact laws of the universe, but are a classical approximation to the more accurate
and fundamental theory of quantum electrodynamics. In most cases, though,

60. Images

61. Traveling Wave Tubes, Klystrons & Magnetrons

Traveling Wave Tubes, Klystrons &
Magnetrons
• Electron Energy magnets and assemblies
are used in sophisticated, performancecritical components of advanced
technology systems, such as traveling
wave tubes (TWTs), klystrons, and
magnetrons.
These are all used to amplify signals at
microwave frequencies for highperforming radar, communications and
electronic countermeasure systems.

62. Waveguides

63. Beam waveguide antenna

• A beam waveguide antenna is a particular
type of parabolic antenna that transports the
signal between a stationary transmitter or
receiver and a movable dish by means of a
beam waveguide. With a conventional "front
fed" parabolic antenna, the antenna feed, the
small antenna that transmits or receives the
radio waves reflected by the dish, is suspended
at a focus, in front of the dish, and moves as the
antenna is repositioned to track specific targets.

64. Internet

• The Internet is a global system of interconnected computer networks that
use the standard Internet protocol suite (TCP/IP) to link several billion
devices worldwide. It is an international network of networks that consists
of millions of private, public, academic, business, and government packet
switched networks, linked by a broad array of electronic, wireless, and
optical networking technologies. The Internet carries an extensive range
of information resources and services, such as the inter-linked hypertext
documents and applications of the World Wide Web (WWW), the
infrastructure to support email, and peer-to-peer networks for file sharing
and telephony.
The origins of the Internet date back to research commissioned by the
United States government in the 1960s to build robust, fault-tolerant
communication via computer networks. While this work, together with
work in the United Kingdom and France, led to important precursor
networks, they were not the Internet. There is no consensus on the exact
date when the modern Internet came into being, but sometime in the early
to mid-1980s is considered reasonable.
From that point, the network experienced decades of sustained
exponential growth as generations of institutional, personal, and mobile
computers were connected to it.

65.

66. TCP/IP

• TCP/IP, Transmission Control Protocol/Internet
Protocol, is a suite of communications protocols
used to interconnect network devices on the
Internet.
TCP/IP implements layers of protocol stacks,
and each layer provides a well-defined network
services to the upper layer protocol. TCP and IP
are the two protocols used by TCP/IP, as well as
the (higher) application, (lower) data link and
(lower) physical layer protocols

67. Decimal to Binary conversion example

68.

69. Parity Bit

• Hamming code
• In communications, parity checking refers to the use of parity bits
to check that data has been transmitted accurately. The parity bit
is added to every data unit (typically seven or eight bits ) that are
transmitted. The parity bit for each unit is set so that all bytes
have either an odd number or an even number of set bits.
Assume, for example, that two devices are communicating with
even parity(the most common form of parity checking). As the
transmitting device sends data, it counts the number of set bits in
each group of seven bits. If the number of set bits is even, it sets
the parity bit to 0; if the number of set bits is odd, it sets the parity
bit to 1. In this way, every byte has an even number of set bits. On
the receiving side, the device checks each byte to make sure that
it has an even number of set bits. If it finds an odd number of set
bits, the receiver knows there was an error during transmission.
The sender and receiver must both agree to use parity checking
and to agree on whether parity is to be odd or even. If the two
sides are not configured with the same parity sense,
communication will be impossible

70. Hamming Codes

• In telecommunication, Hamming codes are a
family of linear error-correcting codes that
generalize the Hamming(7,4)-code invented by
Richard Hamming in 1950. Hamming codes can
detect up to two-bit errors or correct one-bit
errors without detection of uncorrected errors.
By contrast, the simple parity code cannot
correct errors, and can detect only an odd
number of bits in error. Hamming codes are
perfect codes, that is, they achieve the highest
possible rate for codes with their block length
and minimum distance 3

71.

• Due to the limited redundancy that Hamming codes add
to the data, they can only detect and correct errors
when the error rate is low. This is the case in computer
memory (ECC memory), where bit errors are extremely
rare and Hamming codes are widely used. In this
context, an extended Hamming code having one extra
parity bit is often used. Extended Hamming codes
achieve a Hamming distance of , which allows the
decoder to distinguish between when at most one bit
error occurred and when two bit errors occurred. In this
sense, extended Hamming codes are single-error
correcting and double-error detecting, abbreviated as
SECDED.

72. System Software

• Actually, a system software is any computer software which manages and controls
computer hardware so that application software can perform a task. Operating
systems, such as Microsoft Windows, Mac OS X or Linux, are prominent examples of
system software. System software contrasts with application software, which are
programs that enable the end-user to perform specific, productive tasks, such as
word processing or image manipulation.
System software performs tasks like transferring data from memory to disk, or
rendering text onto a display device. Specific kinds of system software include
loading programs, operating systems, device drivers, programming tools, compilers,
assemblers, linkers, and utility software.
Software libraries that perform generic functions also tend to be regarded as system
software, although the dividing line is fuzzy; while a C runtime library is generally
agreed to be part of the system, an OpenGL or database library is less obviously so.
If system software is stored on non-volatile memory such as integrated circuits, it is
usually termed firmware while an application software is a subclass of computer
software that employs the capabilities of a computer directly and thoroughly to a task
that the user wishes to perform. This should be contrasted with system software
which is involved in integrating a computer's various capabilities, but typically does
not directly apply them in the performance of tasks that benefit the user.

73. Application software

• Typical examples of software applications are word processors,
spreadsheets, and media players.
Multiple applications bundled together as a package are sometimes
referred to as an application suite. Microsoft Office and OpenOffice.org,
which bundle together a word processor, a spreadsheet, and several other
discrete applications, are typical examples. The separate applications in a
suite usually have a user interface that has some commonality making it
easier for the user to learn and use each application. And often they may
have some capability to interact with each other in ways beneficial to the
user. For example, a spreadsheet might be able to be embedded in a word
processor document even though it had been created in the separate
spreadsheet application.
User-written software tailors systems to meet the user's specific needs.
User-written software include spreadsheet templates, word processor
macros, scientific simulations, graphics and animation scripts. Even email
filters are a kind of user software. Users create this software themselves
and often overlook how important it is.

74. Thank You-Hope you find it useful

• Source of information: Internet
• World famous Swami Vivekananda(below)