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digital
A digital system
is one that uses numbers,
especially
binary
numbers, for input, processing, transmission, storage, or display,
rather
than a continuous
spectrum of values (an analog
system)
or non-numeric symbols
such as letters
or icons.
The distinction of "digital" versus "analog" or "symbolic" can refer to
method of input, data storage and transfer, the
internal working of an instrument, and the kind of display. The word
comes from the same source as the word digit
and digitus: the Latin
word for finger
(counting on the fingers) as these are used for discrete counting.
The word digital is most commonly used in computing
and electronics,
especially where real-world information is converted to binary
numeric form as in digital
audio and
digital
photography. Such data-carrying signals carry either one of two
electronic
or optical pulses, logic 1 (pulse present) or 0 (pulse absent). The
term is often meant by the prefix "e-", as in
e-mail
and ebook,
even though not all electronics systems are
digital.
Digital noise
When data are transmitted using analog methods, a certain amount of noise
enters into the
signal. This can have myriad causes: data transmitted by radio
may be received badly, suffer
interference
from other radio sources, or pick up background radio noise from the
rest of
the universe. Electric pulses being sent down wires are attenuated by
the resistance of the wire, and dispersed by its
capacitance, and heat variations can increase or reduce these effects.
While digital transmissions are also degraded, any slight
variations can be safely ignored. With an analog signal, any variance
can provide a great amount of distortion. In a digital
signal, these variances can be overcome, as any signal close to a
particular value will be interpreted as that value. Care must
be taken when connecting digital and analog systems; tolerable
variances for the digital part can leak into the analog part and
become intolerable.
Analog, symbolic, and digital displays; ease
of reading
For human readable information, digital,
analog, and symbol display
methods can all be useful. Should an instant impression be
required, analog meters and indicator lights often give information
quickly. Many people glance quickly at their analog watch and
know roughly what the time is or at an automobile dashboard and know
that a door is ajar. When accuracy is required, however,
digital displays are preferred. Reading analog meters requires time and
a little bit of skill, whereas writing down the value on
a digital display is merely a case of copying down the numbers. In
cases where both accuracy and quick reckoning are both
required, dual displays are often used.
A needle (analog) just touching onto
the bottom of an orange shaded area is much different from a needle
almost
touching into the red area, but an indicator lamp (symbol) would
just glow orange and a numeric (digital) display,
although it could be colored orange, would not indicate the relative
level of danger to an untrained operator.
Analog to digital conversion
- Main article: Analog-to-digital
converter
Converting an analog source to digital data
is done with two steps: sampling,
which changes the source to a series of discrete
values (called samples), and quantization,
which converts each sample to a number. For example, the sensor of a
digital camera contains millions of sensing elements (one for each pixel).
When an exposure is
made, the light focused on the array is converted into millions of
electric charges (sampled). These charges are then amplified
and converted to numbers (quantized). The resulting digital
image is then processed and
stored in the camera's memory card. The samples in this case are
spatial. In contrast, converting an audio source to digital
requires temporal samples: it is converted to an electrical signal
using a microphone,
and
the voltage of this signal is sampled thousands of times per second
(the sampling
frequency). Each sample is then quantized to form the digital
audio data.
Both sampling and quantization will result in
a loss of data. Changes in the original data that occur between the
samples will
not appear in the digital data (or worse, will cause aliasing,
the appearance of data not
present in the original source). And while a voltage can be any of a
seemingly unlimited number of values between its minimum and
maximum (limited only by quantum
mechanics), a digital representation using
n bits can have only 2n possible values. While
this information will be preserved in future transmission, the data has
been lost.
The amount of information that can be stored
in a digital representation is called its resolution. And since
the
conversion to digital is a two step process, there are two types of
resolution: sampling resolution and quantization resolution.
Sampling resolution can be either spatial (expressed in pixels
per inch) or temporal
(expressed as samples per second) or both (for example, a video).
Quantization resolution is usually expressed as the number of
bits
used to represent each sample and is thus often called the bit depth or
(for pictures) the
color
depth.
The best resolution for a given set of
digital data depends on the processing it will undergo and its ultimate
purpose. For
example, compact
discs
use a sampling resolution of 44,100 samples/second, which is
sufficient for audio in the range of human hearing. Most digital
photographs use a bit depth of 8 bits/color, which produces more
colors than the human eye can discern. However many photographers use camera
raw with
12 bits/color to allow for more accuracy during processing before
producing a final photograph at 8 bits/color for display or
printing. Scientific photography may also require greater bit depth.
If sufficient resolution is used, the data
loss caused by the conversion to digital is offset by the accuracy of
digital
processing. When analog signals are transmitted and stored, accuracy is
lost due to noise
and distortion.
So neither digital nor analog offer perfect fidelity;
resolution is sacrificed for accuracy with digital and vice versa for
analog. When both high
resolution and high accuracy are needed, either a high resolution
digital system or a high accuracy analog system must be used
(with a correspondingly high cost).
Symbol to digital conversion
Since symbols are not continuous, converting
symbols to digital is simpler and less prone to data loss than analog
to digital
conversion. Instead of sampling and quantization, similar steps are
used: polling
and
encoding.
A symbol input device usually consists of a
number of switches that are polled at regular intervals to see which
switches are
pressed. Data will be lost if, within a single polling interval, two
switches are pressed, or a switch is pressed, released, and
pressed again. This polling can be done by a specialized processor in
the device to prevent burdening the main CPU.
When a new symbol has been entered, the device sends an interrupt
to alert the CPU to read it.
For devices with just a few switches (such as
the buttons on a joystick),
the status of each
can be encoded as bits (usually 0 for released and 1 for pressed) in a
single word. This is very useful when combinations of key
presses are meaningful, and is sometimes used for passing the status of
modifier keys on a keyboard (such as shift and control).
But it does not scale to support more keys than the number of bits in a
single byte or word.
Devices with many switches (such as a computer
keyboard)
usually arrange these
switches in a scan matrix, with the individual switches on the
intersections of x and y lines. When a switch is pressed, it
connects the corresponding x and y lines together. Polling (often
called scanning in this case) is done by activating each x line
in sequence and detecting which y lines then have a signal, thus which
keys are pressed. When the keyboard processor detects that
a key has changed state, it sends a signal to the CPU indicating the
scan code of the key and its new state. The symbol is then
encoded,
or converted into a number, based on the status of modifier keys and
the desired
character
encoding.
Using a custom encoding
for a specific application can be done with no loss of
data. However, using a standard encoding such as ASCII
is problematic if a symbol such as 'ß'
needs to be converted but is not in the standard.
Historical digital systems
Although digital signals are generally
associated with the binary electronic digital systems used in modern
electronics and
computing, digital systems are actually ancient, and need not be binary
nor electronic.
-
A beacon
is perhaps the simplest non-electronic digital signal, with just two
states
(on and off). In particular, smoke
signals are one of the oldest examples of a
digital signal, where an analog "carrier" (smoke) is modulated
with a blanket to generate a
digital signal (puffs) that conveys information.
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DNA
comprises a long sequence of four digits (denoted A,
C, G,
and T),
effectively a
base-four numeral
system. (In fact, in the double
helix structure, there are two strands, but one of them is never
read.) Each of these digits is an organic molecule, known
as a nucleotide.
DNA is the major system of information transfer from one generation to
another, and evolution
has developed its digital properties into a
robust method of
communication.
-
Morse
code
uses five digital states—dot, dash, short gap (between each letter),
medium
gap (between words), and long gap (between sentences)—to send messages
via a variety of potential carriers such as electricity or
light, for example using an electrical
telegraph or a flashing light.
-
Semaphore
signalling uses rods or flags held in particular positions to
send messages to the receiver watching them some distance away.
-
More recently invented, a modem
modulates an analog "carrier" signal (such as sound) to encode
binary electrical digital information, as a series of binary digital
sound pulses. A slightly earlier, surprisingly reliable
version of the same concept was to bundle a sequence of audio digital
"signal" and "no signal" information (i.e. "sound" and
"silence") on magnetic
cassette tape for use with early home
computers.
This entry is from Wikipedia, the leading
user-contributed encyclopedia. It may not have been reviewed by
professional editors (see full disclaimer)
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peasant

In a detail of Brueghel's
Land of Cockaigne
(1567) a soft-boiled egg
has little feet to rush to the luxuriating peasant who catches drops of
honey on his tongue, while roast pigs roam wild: the 16th
century was a good time for European peasants
A peasant, from 15th
century French païsant meaning one from the
pays, the countryside
or region, (from Latin pagus, country district) is an
agricultural
worker with roots in the countryside in which he or she dwells, either
working
for others or, more specifically, owning or renting
and working by his or her own labour a small
plot of ground, in England a "cottager". Peasants exist in a world
before the modern division of labor: a peasant must be a
jack-of-all trades, handy at everything. Peasants depend on the cultivation
of their land;
without stockpiles of provision they thrive or starve according to the
most recent harvest (illustration, above right).
Peasants live to agricultural time; the "world-time", in Fernand
Braudel's term, of
politics and economics does not directly affect the peasant. Peasants
typically make up the majority of the agricultural
labour force in a pre-industrial society.
Though a word of not very strict application,
once a market
economy has taken
universal root, it is now frequently used of the traditionalist rural
population in countries where the land is chiefly held by
smallholders, peasant proprietors.
In the great majority of pre-industrial
societies, peasants constitute the bulk of
the population, the authentic "silent
majority". A rural peasant population differs
enormously in its values and economic behavior from an urban worker
population. Peasants tend to be more conservative
than urbanites, and are often very loyal to inherited power structures
that define their
rights and privileges and protect them from interlopers, despite their
generally low status within them.
Peasant societies generally have very well
developed social support networks. Especially in harder climates,
members of the community who have a poor harvest or suffer some form of
hardship will be taken care of
by the rest of the community. Loyalties
and vengeance
both run
very deep. Peasant communities are extremely tight, and are often
difficult to access or understand by outsiders.
Peasant societies can often have very stratified
social hierarchies within them.

Sedentary Occupations of the
Peasauts.--Facsimile from an Engraving on Wood, attributed to Holbein,
in the "Cosmographie" of
Munster (Basle, 1552, folio).
In a barter
economy, peasants characteristically have a different attitude to
work than
peasants— or towndwellers— in a money
economy would. Most of them are content to live at a
subsistence level and will not expend unnecessary labour raising their
standard of living. Traditionally many non-peasants have
viewed this as laziness. However, it does make sense from their
perspective, since there would rarely be any point in producing
more than could be consumed.
Fernand
Braudel devoted the first volume of his major work, Civilization
and
Capitalism 15th–18th Century to the largely silent and invisible
world that existed below the market economy, in The
Structures of Everyday Life.
Since the literate classes who left the most
record tended to
dismiss the peasants as figures of coarse appetite and rustic
comedy, "peasant" may have a pejorative rather than descriptive
connotation in historical memory. However, it was not always that
way; peasants were once viewed as pious and seen with respect and
pride. Life was hard for peasants, but before technology and a
money economy created a chasm
between rich and poor, life was hard for everyone. Society was
theorized as organized in three "estates": those who work, those who
pray and those who fight. Those who theorized did so for
those whose recent ancestors did little but fight, ecclesiastics and
nobles who increasingly lived more private lives. A new
consciousness of inalienable rights and new, unjust impositions from
above contributed to the popular
(or peasant) uprisings of the 14th century,
the breakdown of the feudal
system and the rise of modernity. Once a money economy had intruded on
the old agricultural order, the peasant was slowly
transformed into the laborer for wages, or he might hold a precarious
position as an independent smallholder, one of the "yeomen"
of sentimental history.
In some countries in central and eastern
Europe where a barter economy obtained in self-sufficient societies,
reintroduced
serfdom
continued up to the 19th century in places, and in some third world
countries the term
is still broadly applicable today.
Peasant Sayings
-
"Arbeit
macht frei" German peasant saying that means "Work makes free"
literally,
but conveys the meaning "Labor/Work liberates."
This entry is from Wikipedia, the leading
user-contributed encyclopedia. It may not have been reviewed by
professional editors (see full disclaimer)
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Translations for:
Digital
Nederlands (Dutch)
digitaal (in cijfers)
Français (French)
digital, numérique, à affichage numérique, touche
(du piano)
Deutsch (German)
adj. - digital
n. - Taste
Ελληνική (Greek)
adj. ψηφιακός n. δάκτυλο(ς), (μουσ.) πλήκτρο
Italiano (Italian)
digitale
Português (Portuguese)
adj. - digital
n. - tecla (f) (de instrumento)
Русский (Russian)
цифровой
Español (Spanish)
adj. - digital, que usa dígitos
n. - dígito, formato digital
Svenska (Swedish)
adj. - digital
n. - digital-
中国话 (Simplified Chinese)
adj. - 数字的
n. - 数字, 数字式
中國話 (Traditional Chinese)
adj. - 數位的
n. - 數位, 數位式
日本語 (Japanese)
n. - 指, 鍵, デジタル
adj. - 指の, 指のある, 数字で表示する, 数字で計算する
العربيه (Arabic)
(صفه) رقمي, إصبعي ( ذو علاقه
بأصابع اليد أو القدم) (الاسم) إصبع أو مفتاح في الأرغن ( يضغط عليه بإصبع
اليد لإصدار نغم)
עברית (Hebrew)
adj. - ספרתי, דיגיטלי, של אצבע
n. - מקש, קליד
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Translations for:
Peasant
Nederlands (Dutch)
boer, lomperd
Français (French)
paysan
Deutsch (German)
n. - Bauer, Landarbeiter
adj. - Bauern-, bäurisch
Ελληνική (Greek)
n. χωρικός, χωριάτης, αγρότης adj. χωριάτικος, χωριάτης
Italiano (Italian)
contadino
Português (Portuguese)
n. - camponês (m), lavrador (m)
adj. - rural
Русский (Russian)
крестьянин
Español (Spanish)
n. - campesino, labrador, labriego
adj. - campesino, labrador
Svenska (Swedish)
n. - bonde, jordbrukare, lantis, bondtölp
adj. - allmoge-
中国话 (Simplified Chinese)
n. - 农夫, 乡下人
中國話 (Traditional Chinese)
n. - 農夫, 鄉下人
日本語 (Japanese)
n. - 農夫, 小作農, 田舎者
العربيه (Arabic)
(الاسم) قروي, فلاح (صفه) فلاحي,
ريفي خلوي
עברית (Hebrew)
n. - איכר, בור, גס
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